A new Yahoo! group and mailing list have been established for BT Vision/ HomePlug/ PLC interference victims in the UK, and anyone else worldwide who wants to help formulate strategies for preserving the HF listening hobby in all countries. It is at:
http://tech.groups.yahoo.com/group/UKQRM/
Other Links:
British Telecom
BT Vision (all this trouble for us, so people can watch Desperate Housewives in the bedroom)
BT Group Wiki Entry (we're a long way from the post office!)
BT Vision Wiki Entry
Typical UK interference problem
British OfCom Investigations
Taiwanese mfr of the DH-10PF
AcBel spec sheet
Why the 200 MB claim by the mfr AND in the BT web store is false advertising
The BPL/PLC industry's side of the story
What the interference sounds like
OfCom complaint web page
Severe interference in Hobart, Australia (YouTube video)
Sunday, July 06, 2008
Friday, July 04, 2008
HomePlug/ PLC no stranger to ARRL
It appears that certain modest efforts have been made to protect US amateurs from this assault on HF radio. Unfortunately, these do not cover the rest of HF, and also (according to UK listeners), they don't prevent all of the noise, just the loudest stuff.
Here's something from ARRL:
It seems evident that we must now create a similar problem for these manufacturers. It is NOT OK to shift the problem onto other radio services that aren't as well organized. We need this technology OFF HF!
Here's something from ARRL:
Even if measurements are made correctly at 30 meters, the absolute maximum limits in the Part 15 rules are high enough that harmful interference is likely. Those S9+ level signals from otherwise legal Part 15 radiators would cause harmful interference to almost all received amateur signals.
Although a manufacturer is responsible only for meeting those limits, in many cases, they end up assuming some responsible for harmful interference on behalf of their customers. As a minimum, there are very real costs associated with dealing with interference complaints, and as word of mouth about widespread interference spreads, it could well have an effect on product sales.
Many trade associations for similar products have recognized the need to offer additional protection to radio services that might be found near their products. For systems deployed in residential neighborhoods, it is quite likely that these systems will have nearby amateur radio operators.
Over the past few years, ARRL has worked closely and productively with several of these organizations. As a result of joint testing performed with ARRL, HomePlug has chosen to include a spectral mask (notches) in the HF ham bands. (There were a number of amateurs on the HomePlug working groups who well understood why it was in their employer’s best interests to avoid widespread interference from their products.)
Although there is still some potential for interference, the specification has reduced their signal levels in the ham bands about 30 dB below what is required under Part 15. HomePlug chose to add the spectral masks to avoid the potential for widespread harmful interference to Amateur Radio in areas near HomePlug systems.
It seems evident that we must now create a similar problem for these manufacturers. It is NOT OK to shift the problem onto other radio services that aren't as well organized. We need this technology OFF HF!
Thursday, July 03, 2008
More on the enemy - it's the Universal Powerline Assn
Here's what we are up against. Thanks to Wikipedia (boldface mine):
Anyone who thinks this trend is peculiar to the UK has not been following developments in this technology. Hundreds of thousands of these adapters are being deployed all over Europe.
From Eurocom:
Here's more on the UPA, which is the enemy:
Here is the FAQ on the UPA's own site. It makes the magnitude of the struggle facing us only too stark.
It should be obvious to everyone that this technology is starting to deploy worldwide. While we worried about power companies putting RF into their lines, we missed telephone companies putting it into home wiring. We have catching up to do. It is best that we do it, or there will be no more HF.
The BT Vision Box is a rebranded Philips DIT9719 operating Microsoft Mediaroom software, and requires the BT Home Hub and BT Broadband internet. That said, a number of customers are using alternatives to the BT Home Hub without problems[citation needed].
The set-top box is connected to the hub via an ethernet cable either connected directly to the BT Home Hub, or to one of a pair of Comtrend UPA (Universal Powerline Association) compliant Ethernet adapters. The Comtrend UPA adaptors use the mains wiring in a house to create an ethernet network. A second adaptor is plugged into the mains and connected to the BT Home Hub via an ethernet cable. These plugs are provided as part of the BT Vision package. Additional Comtrend adaptors are available from BT so that a local area network can be created in the users home.
Anyone who thinks this trend is peculiar to the UK has not been following developments in this technology. Hundreds of thousands of these adapters are being deployed all over Europe.
From Eurocom:
15 October, 2007 13:59
Comtrend delivers 590,000 PLC solutions for Europe in 2007
Comtrend Corporation, a network solutions manufacturer and broadband, VoIP and data networks technologies specialist, has announced the delivery of 590,000 200-Mbps PLC Ethernet adapters, the PowerGrid DH-10PF, by the end of 2007. The solutions will be supplied to the English, Spanish and Portuguese markets respectively, making Comtrend the first international manufacturer capable of delivering such a high volume of PLC Ethernet adapters.
[Similar problems are reported by radio users in Spain and Portugal. -hugh]
In 2006, Comtrend Corporation also opened an office in Central Europe and confirmed its development in several countries within Northern Europe.
Developed in partnership with DS2, a PLC solutions specialist, Comtrend's PowerGrid DH-10PF establishes broadband home networks for sharing data, sound and high-definition TV content. In compliance with the 200-Mbps PLC standard supported by the UPA (Universal Powerline Association), to which Comtrend and DS2 belong, the DS2 PLC technology built into the PowerGrid DH-10PF helps to provide a solution cutting out dead spots, while delivering the speed and quality of service required for distributing video throughout the home.
Here's more on the UPA, which is the enemy:
• Universal Powerline Association (UPA)
– The Universal Powerline Association (UPA) is an International association working to harmonize global standards and regulations in the fast developing power line communications market. Power Line Communications (PLC) is a technology that utilizes existing electrical distribution lines, whether in-building or out in the
utility’s distribution system, for delivering high-speed communications services
– www.upaplc.org
• Wide Alliance of Industry Support
– Predominantly used in Europe and South America
– Single source vendor today (DS2)
– Alliance consist of silicon manufacture, system operators and system integrators
• Field Proven Home Networking Technology
– Over one million PLC chips shipped
– Selected by Belgacom, British Telecom, Telecom Italia & Telefonica as the main home networking technology
Here is the FAQ on the UPA's own site. It makes the magnitude of the struggle facing us only too stark.
It should be obvious to everyone that this technology is starting to deploy worldwide. While we worried about power companies putting RF into their lines, we missed telephone companies putting it into home wiring. We have catching up to do. It is best that we do it, or there will be no more HF.
HF: Defend It or Lose It!
I have never been more serious than right now. The use of HF radio is OVER unless all of us organize and fight with a single voice.
The situation:
Everyone wants high speed Internet access and digital video on demand. The current Internet cannot carry all this information. Whoever solves this problem will become very wealthy indeed, and will also have made a major contribution.
Unfortunately, in the rush to open up new information pipelines, a number of ill-conceived or self-serving schemes have emerged. For our purposes in the radio hobby, the worst of these is communication using power lines, which almost always involves putting wideband RF energy into ready-made antennas by any other name.
We haven't learned to live with BPL (Broadband Over Power Lines) yet, but now there is a far worse problem. It's PLC (Power Line Communication), and it's taking off like wildfire in Europe and South America. It's supported by the United Powerline Association, a global industry association with several very powerful and influential corporate members.
The first I knew that anything had gone badly, nightmarishly wrong was when two of this column's contributors in the UK suddenly stopped doing radio altogether. They reported huge blasts of high-pitched noise, hash, and general crud blanketing everything pretty much from DC to daylight.
Since this was new to the UK, it took a while to figure out what was going on there. What's happening is that British Telecom (BT; a phone company that also operates HF comm sites, and thus should know better) is providing its customers with power line adapters which send Ethernet through the house wiring. Not the power company's lines, but the wires in your house.
You plug one adapter from the Internet/Video on Demand box (called a BT Home Hub) into the power line, and plug in the second one near a television you want to use for the video.
It is probably well known to most technically aware people that Ethernet is basically RF. These adapters are broadband HF transmitters which turn your house into a giant radio station which can radiate hundreds of feet.
These are being made by the usual companies, and being widely promoted as the solution to the previous expense of running Ethernet cables through homes. These things will undoubtedly spread worldwide if they are not stopped right now.
The future:
It's not hard to imagine the result of millions of these gadgets being installed all over populated areas. The side effect will be the worldwide deployment the most effective HF jammer ever invented. It will create vast areas in our populated regions that are little more than HF exclusion zones. The HF spectrum, which used to belong to the public by way of its national and international licensing bodies, will have been hijacked!
As long as there's a buck to be made, there will be influential people and companies seeking to send RF through any available conductors for computer networking and digital media. Wires were designed to conduct electricity, fence off property, etc etc. They were never intended to be used in place of cable or Cat5 twisted pair. When used in this manner, they become antennas. It's simple physics.
The only conclusion:
HF is over unless we fight for it. As a hobby, we must become as united as the corporations we need to fight. We must make it clear that denying the use of internationally regulated radio services so that someone else can profit from cheap, badly designed consumer electronics is NEVER all right - EVER.
Let's get started.
The situation:
Everyone wants high speed Internet access and digital video on demand. The current Internet cannot carry all this information. Whoever solves this problem will become very wealthy indeed, and will also have made a major contribution.
Unfortunately, in the rush to open up new information pipelines, a number of ill-conceived or self-serving schemes have emerged. For our purposes in the radio hobby, the worst of these is communication using power lines, which almost always involves putting wideband RF energy into ready-made antennas by any other name.
We haven't learned to live with BPL (Broadband Over Power Lines) yet, but now there is a far worse problem. It's PLC (Power Line Communication), and it's taking off like wildfire in Europe and South America. It's supported by the United Powerline Association, a global industry association with several very powerful and influential corporate members.
The first I knew that anything had gone badly, nightmarishly wrong was when two of this column's contributors in the UK suddenly stopped doing radio altogether. They reported huge blasts of high-pitched noise, hash, and general crud blanketing everything pretty much from DC to daylight.
Since this was new to the UK, it took a while to figure out what was going on there. What's happening is that British Telecom (BT; a phone company that also operates HF comm sites, and thus should know better) is providing its customers with power line adapters which send Ethernet through the house wiring. Not the power company's lines, but the wires in your house.
You plug one adapter from the Internet/Video on Demand box (called a BT Home Hub) into the power line, and plug in the second one near a television you want to use for the video.
It is probably well known to most technically aware people that Ethernet is basically RF. These adapters are broadband HF transmitters which turn your house into a giant radio station which can radiate hundreds of feet.
These are being made by the usual companies, and being widely promoted as the solution to the previous expense of running Ethernet cables through homes. These things will undoubtedly spread worldwide if they are not stopped right now.
The future:
It's not hard to imagine the result of millions of these gadgets being installed all over populated areas. The side effect will be the worldwide deployment the most effective HF jammer ever invented. It will create vast areas in our populated regions that are little more than HF exclusion zones. The HF spectrum, which used to belong to the public by way of its national and international licensing bodies, will have been hijacked!
As long as there's a buck to be made, there will be influential people and companies seeking to send RF through any available conductors for computer networking and digital media. Wires were designed to conduct electricity, fence off property, etc etc. They were never intended to be used in place of cable or Cat5 twisted pair. When used in this manner, they become antennas. It's simple physics.
The only conclusion:
HF is over unless we fight for it. As a hobby, we must become as united as the corporations we need to fight. We must make it clear that denying the use of internationally regulated radio services so that someone else can profit from cheap, badly designed consumer electronics is NEVER all right - EVER.
Let's get started.
No New HFDL Ground Station
I'm receiving New York squitters now, but there is no mention of a new ground station, and others report that it is no longer being sent. Perhaps confusion in the HFDL system, now resolved?
New HFDL Ground Station?
Nothing from ARINC, but several HFDL ground stations are mentioning a new ground station called UNKNOWN in their squitters. Unfortunately, the closest one to The Land That Short Wave Forgot is New York, and there's not propagation from there yet. We'll try to get some more information.
Tuesday, July 01, 2008
CW Night of Nights in 11 days!
The annual Maritime Radio Historical Society "Night of Nights" event is less than one month [two weeks now -hugh] away.
Every year on 12 July (US time) many famous coast stations return to the air to commemorate the closure of commercial Morse in the USA. This year stations KPH, KFS, KSM and KLB have confirmed they will be on the air. We hope that US Coast Guard stations NMC, NOJ and NMN will join us as they did last year.
Amateur station K6KPH will guard 3550, 7050 and 14050kc for reception reports.
Preliminary information has been posted on the MRHS Web site: http://www.radiomarine.org
Check back often for updated information as it becomes available.
If you would like to receive announcements like this and are not already a member of our mailing list just send a message to: radiomarine-subscribe@yahoogroups.com
VY 73,
RD
=================================
Richard Dillman, W6AWO
Chief Operator, Coast Station KSM
Maritime Radio Historical Society
http://www.radiomarine.org
=================================
Thursday, June 26, 2008
"Digital" Mode of the Week: HF FAX
FAX stands for facsimile, or in this case radiofacsimile. Unlike the more recently developed office FAX machines used over wire telephone circuits, it is completely analog, using FM emission (F3C). It dates from work done by various inventors in the late 19th and early 20th centuries to send pictures over telegraph and later radio.
HF FAX was very widely used in the 20th century to send news photos and even entire newspapers over HF point to point circuits. Machines used huge drum scanners and similar drums to print at the other end. They were very precise, and very, very expensive. Now it can be done with simple computer sound card software, though at considerable loss of precision in this rather fussy mode.
Today's HF FAX uses a continuous FM carrier with a narrow 800-Hz deviation. Usually, anything around 1500 Hz, the lower limit, is reproduced as black, with the brightness increasing until it reaches a white point up around the high limit of 2300 Hz. By ear, fax can make a number of different sounds, but usually it makes a cyclic pulsing with a high-pitched shreik underneath.
Nowadays, instead of using true FM transmitters, the corresponding baseband audio tone is sent to a normal, single-sideband, suppressed-carrier, HF transmitter. The result sounds the same, only displaced in frequency due to the offset from the missing carrier. FAX is tuned in USB, or else it will reproduce as a negative, and the dial should read 1.9 kHz (the tone center) lower than published frequencies. Most of the time, one centers the waterfall display between two marks, and it's tuned in. Slight mistuning has no effect except to possibly wash out the blacks or whites, depending on which direction it is.
Two other parameters are essential for the reception of FAX. The first is called drum speed, though obviously nowadays transmission speed would be a better name. It's expressed in lines per minute. The receiving software must sync to this speed, or the pictures will not reproduce properly.
Far, far the most common speed is 120 LPM. It is used for nearly all weather FAX. Some more complex pictures are sent at 60 LPM, a speed which can sound like a time signal.
The second parameter is Index of Cooperation (IOC), expressed as an integer. This is a really arcane thing also dating from the use of drum scanners. It measures the resolution of the FAX. Nobody really has to know what the IOC measures, just what the number is, and it is nearly always 576. On very rare occasion, it's 288. This is way less important for computer screens than it is for rotating drums.
Those who are really curious as to just what the Index of Cooperation is will be pleased to know that it's commonly defined as the product of the total line length and the number of lines per unit length, divided by Pi. It's measuring the ratio of how much distance the scan steps for a new line to the diameter of the drum. The length of time any single FAX can last is determined proportional to the IOC. At 120/576, the standard weather format, this is 18.8 minutes, which is plenty. Going to 60/576 doubles this, along with increasing resolution, though of course the fax takes twice as long to send.
Now it's all clear, right? :-)
Most FAX software allows the setting of black and white or continuous tone (grey scale) modes. Except for satellite weather images, just about every FAX sent on HF nowadays is in black and white. I'll get some argument here, but I've always just kept it on continuous anyway. Otherwise lines get kind of jagged, and typical HF ionospheric multipath fuzz can get grungy looking in a hurry. Plus you have to change it whenever a satellite image is sent, and then change it back again.
Radiofax typically uses a standard called APT (Automatic Picture Transmission). This allows the unattended reception of faxes. Different bands and services use different versions of this, but the one we're interested in is as follows:
5 sec Start Tone (alternate black and white at 300 Hz)
Phasing (30 seconds of white with one black pulse per line)
Image (may have a white interval for sync)
5 sec Stop Tone (alternate black and white at 450 Hz)
Optional 10 sec black
Different agencies have slight variations on this, and these are usually just enough to confuse amateur software. Even so, one will notice that all the information needed to set parameters and receive faxes is here, except maybe for IOC and that's almost always 576 anyway.
Why more computer programs don't take advantage of this is beyond me. They don't however, and so your received fax is usually displaced (left edge is somewhere else in the screen) and slanted (computer is not printing lines at the exact speed of transmission). There are nearly always ways to fix these, either during or after reception.
Slant is way the more annoying of the two, because computer sound cards really aren't up to the task. They don't have the tight frequency tolerance that an expensive dedicated device would have. Typically, the proper slant compensation has to be found manually for a given station, and then it will vary for others, or even change during a long FAX.
I like FAX because it's radio with pictures. One learns how to read the weather charts pretty fast. They're not that different than the ones on the Weather Channel. Also, the satellite images are as good as the ones on your local TV, and better if you get into colorized WEFAX downlinking on higher frequencies.
Many coast guards and weather offices still send hours of these a day, and since they are being used by boats for serious navigation and safety of life at sea, they won't go away any time soon. Check the various lists and radio loggings for something audible in your area.
HF FAX was very widely used in the 20th century to send news photos and even entire newspapers over HF point to point circuits. Machines used huge drum scanners and similar drums to print at the other end. They were very precise, and very, very expensive. Now it can be done with simple computer sound card software, though at considerable loss of precision in this rather fussy mode.
Today's HF FAX uses a continuous FM carrier with a narrow 800-Hz deviation. Usually, anything around 1500 Hz, the lower limit, is reproduced as black, with the brightness increasing until it reaches a white point up around the high limit of 2300 Hz. By ear, fax can make a number of different sounds, but usually it makes a cyclic pulsing with a high-pitched shreik underneath.
Nowadays, instead of using true FM transmitters, the corresponding baseband audio tone is sent to a normal, single-sideband, suppressed-carrier, HF transmitter. The result sounds the same, only displaced in frequency due to the offset from the missing carrier. FAX is tuned in USB, or else it will reproduce as a negative, and the dial should read 1.9 kHz (the tone center) lower than published frequencies. Most of the time, one centers the waterfall display between two marks, and it's tuned in. Slight mistuning has no effect except to possibly wash out the blacks or whites, depending on which direction it is.
Two other parameters are essential for the reception of FAX. The first is called drum speed, though obviously nowadays transmission speed would be a better name. It's expressed in lines per minute. The receiving software must sync to this speed, or the pictures will not reproduce properly.
Far, far the most common speed is 120 LPM. It is used for nearly all weather FAX. Some more complex pictures are sent at 60 LPM, a speed which can sound like a time signal.
The second parameter is Index of Cooperation (IOC), expressed as an integer. This is a really arcane thing also dating from the use of drum scanners. It measures the resolution of the FAX. Nobody really has to know what the IOC measures, just what the number is, and it is nearly always 576. On very rare occasion, it's 288. This is way less important for computer screens than it is for rotating drums.
Those who are really curious as to just what the Index of Cooperation is will be pleased to know that it's commonly defined as the product of the total line length and the number of lines per unit length, divided by Pi. It's measuring the ratio of how much distance the scan steps for a new line to the diameter of the drum. The length of time any single FAX can last is determined proportional to the IOC. At 120/576, the standard weather format, this is 18.8 minutes, which is plenty. Going to 60/576 doubles this, along with increasing resolution, though of course the fax takes twice as long to send.
Now it's all clear, right? :-)
Most FAX software allows the setting of black and white or continuous tone (grey scale) modes. Except for satellite weather images, just about every FAX sent on HF nowadays is in black and white. I'll get some argument here, but I've always just kept it on continuous anyway. Otherwise lines get kind of jagged, and typical HF ionospheric multipath fuzz can get grungy looking in a hurry. Plus you have to change it whenever a satellite image is sent, and then change it back again.
Radiofax typically uses a standard called APT (Automatic Picture Transmission). This allows the unattended reception of faxes. Different bands and services use different versions of this, but the one we're interested in is as follows:
5 sec Start Tone (alternate black and white at 300 Hz)
Phasing (30 seconds of white with one black pulse per line)
Image (may have a white interval for sync)
5 sec Stop Tone (alternate black and white at 450 Hz)
Optional 10 sec black
Different agencies have slight variations on this, and these are usually just enough to confuse amateur software. Even so, one will notice that all the information needed to set parameters and receive faxes is here, except maybe for IOC and that's almost always 576 anyway.
Why more computer programs don't take advantage of this is beyond me. They don't however, and so your received fax is usually displaced (left edge is somewhere else in the screen) and slanted (computer is not printing lines at the exact speed of transmission). There are nearly always ways to fix these, either during or after reception.
Slant is way the more annoying of the two, because computer sound cards really aren't up to the task. They don't have the tight frequency tolerance that an expensive dedicated device would have. Typically, the proper slant compensation has to be found manually for a given station, and then it will vary for others, or even change during a long FAX.
I like FAX because it's radio with pictures. One learns how to read the weather charts pretty fast. They're not that different than the ones on the Weather Channel. Also, the satellite images are as good as the ones on your local TV, and better if you get into colorized WEFAX downlinking on higher frequencies.
Many coast guards and weather offices still send hours of these a day, and since they are being used by boats for serious navigation and safety of life at sea, they won't go away any time soon. Check the various lists and radio loggings for something audible in your area.
More from Charles Brain on the Vista Problem
Charles:
Hello Vista users,
I have done a Google search and it seems that the problem is due to the fact that Microsoft have moved the sound drivers from Kernel space to user space. This has caused the hardware acceleration used by some cards to stop working. Accurate information on this problem is very difficult to come by.
It seems the reason that Microsoft did this was to protect Vista from errant sound card drivers not under their control. They were getting fed up with being blamed for crashes that weren't their fault. There are some other reasons for wanting to move the drivers to user space I have been told.
At the moment I can't see any short term fix to this problem as it appears to be outside my control. I understand that this problem is causing a lot of grief among P.C gamers too as they have lost some of their special sound effects.
I am guessing here but what I think is happening is that when I ask for a 48K sample rate the card is returning something else (possibly 44.1K) and that is why it does not work. I base this guess on the fact that I can get PC-HFDL to start on a Vista laptop and display hfdl packets on the spectrum display (indicating the sound handling is working) what it does not do is decode the actual packets (indicating a sample rate problem).
I am sorry I can't be any more helpful/hopeful than that.
- Charles
Thursday, June 19, 2008
Annual VLF Alternator Transmission Coming Up
The Alexanderson Alternator was the first continuous-wave CW transmitter. It is literally a large electric motor-generator that makes RF. A global network of these huge stations was rapidly replacing "King Spark" for maritime coastal radio, when vacuum tubes replaced both.
A working example is at SAQ, Grimeton Radio. RF power is on the order of 200 kW, but the frequency is so low (17.2 kHz, not MHz) as to make it a real catch in North America. From the web site in Sweden:
A working example is at SAQ, Grimeton Radio. RF power is on the order of 200 kW, but the frequency is so low (17.2 kHz, not MHz) as to make it a real catch in North America. From the web site in Sweden:
GRIMETON RADIO/SAQ TRANSMISSION
The annual transmission on "Alexanderson Day" with the Alexanderson alternator on VLF 17.2 kHz will take place Sunday 29th June 2008 at 09:00 UTC (tuning up from after 08:00 UTC) and will be repeated at 13:00 UTC (tuning up from after 12:00 UTC).
The station will be open to visitors.
Amateur Radio Station with special event call "SK6SAQ" will be QRV 09:15 -12:00 UTC on the following frequencies:
- 14.035 kHz CW
- 14.215 kHz SSB
>From 07:00 UTC also on:
- 3.755 kHz SSB.
QSL via SK6DK or direct to address below.
QSL-reports to SAQ and SK6SAQ are kindly received:
- E-mail to: info@alexander.n.se
- or fax to: +46-340-674195
- or via: SM bureau
- or direct by mail to: Alexander - Grimeton Veteranradios Vaenner,
Radiostationen
Grimeton 72
SE-430 16 ROLFSTORP
S W E D E N
Charles Brain: Bad News for PC-ALE Under Vista
From the hflink group on Yahoo:
Hello Folks,
Well I have done yet another Google search to try and find why programs like PC-ALE won't work properly under Vista.
All I can find is that the Microsoft Vista sound development team have completely re-written the Sound subsystem, they have moved it from Kernel space to User space. Apparently the reason they did this was because Microsoft was being blamed for OS crashes by errant sound drivers that were not their fault.
The side effect of this change has been to disable hardware acceleration in a number of soundcards most notably Creative Devices ones. Creative got around the problem by using their version of ALchemy.
I have not tried this but it might help.
Unfortunately this problem with Vista goes places in Windows that I fear to tread so unless some genius comes up with a simple fix Vista support for PC-ALE will never happen. It seems like the only cards that stand a chance of working are the simplest ones with no hardware acceleration.
Looks like my next project will be Linux based!
- Charles
Wednesday, June 11, 2008
Baltops Participating Units
From German Navy:
The multinational Baltic maneuver BALTOPS 2008, a total of 47 international units from 13 different nations.
Dänemark
HDMS OLFERT FISCHER
HDMS VIBEN
HOMEGUARD CUTTERS
RHIBS
EOD TEAM
Deutschland
FGS BAYERN
FGS ELBE
FGS S 72 PUMA
FGS U 15
FGS S 80 HYÄNE
FGS ENSDORF
24 Minen
1x PC-9 Pilatus
1x MPA
2x TORNADO
SubOPauth
MAO C
Estland
BALTRON
Finnland
FNS RAAHE
FNS NAANTALI
Frankreich
FS LOIRE
FS CROIX DE SUD
FS ERIDAN
EOD TEAM
Lettland
LVNS VIESTURS
Litauen
LNS JOTVINGIS
Niederlande
HNLMS MAASLUIS
HNLMS MAKKUM
HNLMS VLAARDINGEN
HNLMS WILLEMSTAD
RNLNA KINGSBERGEN
Polen
ORP GROM
ORP MAMRY
ORP WIGRY
ORP SOKOL
Russland
RFS NEUSTRASHIMY
RFS KALININGRAD
RUS SU-24
RUS SEA BASED HELIX
RUS LAND BASED HELIX
Schweden
HSWMS SKAFTOE
Großbritannien
HMS BULWARK
Vereinigte Staaten von Amerika
USS GETTYSBURG
USS COLE
USNS PATUXENT
1x MPA
NATO Baltops Exercise Under Way
5102.5 lit up with US and German participating units. Norwegian navy also heard. Expect tactical comm on many European frequencies. NUKO formatting and unit calling NAA. Sounds like old times.
Friday, June 06, 2008
Digital Mode of the Week: PSK31 (Part 2 - Phase-Shift Keying)
PSK31 was developed in 1998 by Peter Martinez, a British ham with the call G3PLX. It was intended to improve on RTTY for the purpose of direct, keyboard-to-keyboard contacts and rag chews. PSK stands for Phase-Shift Keying, and 31 refers to the baud rate of 31.25. This sounds slow, but it is perfect for hand typing, and it was also easy to count down from the 8000-Hz sample rate common for sound cards of the era.
Unlike many digital modes, which continued to be somewhat esoteric for ham use, PSK31 caught on immediately. From very early on, it was extremely well suited for generating and decoding with user-friendly, sound card software on ordinary personal computers. In use, the mode proved to be very efficient in its use of power and spectrum, allowing hams to communicate on HF without the equipment taking over their lives (and pocketbooks).
Right now, one can tune to 14070 kHz any time the band is open and find multiple signals all warbling away. Often it sounds like an attack from extraterrestrial science fiction insects. Less active frequencies are 10138-40 and 7035.
While PSK31 can have different modulation schemes, the one most commonly used is Binary Phase-Shift Keying (BPSK). Data is transmitted by commanding the sound card to shift the phase of the baseband audio signal by 180 degrees, in effect inverting the polarity.
Ordinarily, this would create a tremendous key click, but the amplitude is synchronously shaped by cosine modulation at the same time. The result is a best-case bandwidth for a PROPERLY MODULATED signal that is theoretically equal to the baud rate - yes, 31.25 hertz!! That is narrower than "hard" on-off keyed CW at a comparable 50 WPM.
Of course, things in the real world are somewhat more complicated. As can be easily seen on the waterfall, many signals have varying amounts of clicking or IM audio distortion, and they are maybe 40 or 50 Hz wide. This gets worse if the operator is hitting it too hard and causing more sidebands to appear. For the most part, though, PSK31 is one of the narrowest modes ever designed for hams.
The narrow bandwidth and low data rate make PSK31 practically immune to selective ionospheric fading (that Moog whooshing sound you hear on wider modes like HFDL and STANAG 4285). It performs less well under phase and Doppler distortion such as from aurora.
In this keying system, any phase flip signals a 0 bit. If there's no shift at the right time, it's a one bit. As we've seen, the state doesn't matter, it's the change in state. Again, it can be tuned in USB or LSB, though USB is traditional.
A character space is two zeroes - 00. This is why all the characters end in 1.
The PSK31 idler consists of all zeroes, which flip the phase at the baud rate. This and the cosine shaping produce what is basically double-sideband suppressed-carrier emission (J2B). ITU refers to it as 60H0J2B, in the long international designators. This means suppressed-carrier modulation for automatic reception using a maximum channel width of 60 hertz.
The transmission starts with a distinctive railroad track pattern on the waterfall. Bursts of hand typing create something looking more like a DNA molecule. At the end of the transmission, it all collapses back into the single tone.
Receiving consists of syncing to the baud rate, which is determined from the signal, and sending the resulting data to a Viterbi decoder. There are no connections, and no error checks. Stations take turns sending, just like RTTY. Character hits print gibberish, again like RTTY. However, the copy is usually much better on HF, everything else being equal.
There's not much else to know. BPSK31 is very uncomplicated to the user. You click on a signal and copy comes out.
PSK31 immediately gave rise to a bewildering array of phase-shift keyed, character-based, half-duplex modes. If you've used MultiPSK you know what I'm talking about. Each new version has more little buttons and more funny noises than the last one. Since decode sync is determined from the signal, there's also an autodetect mode.
An early variant that should be in just about all PSK31 software is QPSK31. This stands for quaternary phase-shift keying. On the standard computer phase constellation display, you will see four points instead of two. This is done through the use of a second BPSK carrier shifted 90 degrees (in quadrature), driving a second receive demodulator.
While this should double throughput, the extra capacity is used for an error check and more robust decoding. The performance of this mode on degraded circuits is impressive, but at the cost of more bandwidth and a tuning precision challenging even modern solid-state radios.
Other BPSK and QPSK modes are at 10, 63, 125, and 250 baud. There's also PSK220F, a 220-baud mode well adapted to broadcasting. It is used by the Cuban numbers operation at times.
Unlike many digital modes, which continued to be somewhat esoteric for ham use, PSK31 caught on immediately. From very early on, it was extremely well suited for generating and decoding with user-friendly, sound card software on ordinary personal computers. In use, the mode proved to be very efficient in its use of power and spectrum, allowing hams to communicate on HF without the equipment taking over their lives (and pocketbooks).
Right now, one can tune to 14070 kHz any time the band is open and find multiple signals all warbling away. Often it sounds like an attack from extraterrestrial science fiction insects. Less active frequencies are 10138-40 and 7035.
While PSK31 can have different modulation schemes, the one most commonly used is Binary Phase-Shift Keying (BPSK). Data is transmitted by commanding the sound card to shift the phase of the baseband audio signal by 180 degrees, in effect inverting the polarity.
Ordinarily, this would create a tremendous key click, but the amplitude is synchronously shaped by cosine modulation at the same time. The result is a best-case bandwidth for a PROPERLY MODULATED signal that is theoretically equal to the baud rate - yes, 31.25 hertz!! That is narrower than "hard" on-off keyed CW at a comparable 50 WPM.
Of course, things in the real world are somewhat more complicated. As can be easily seen on the waterfall, many signals have varying amounts of clicking or IM audio distortion, and they are maybe 40 or 50 Hz wide. This gets worse if the operator is hitting it too hard and causing more sidebands to appear. For the most part, though, PSK31 is one of the narrowest modes ever designed for hams.
The narrow bandwidth and low data rate make PSK31 practically immune to selective ionospheric fading (that Moog whooshing sound you hear on wider modes like HFDL and STANAG 4285). It performs less well under phase and Doppler distortion such as from aurora.
In this keying system, any phase flip signals a 0 bit. If there's no shift at the right time, it's a one bit. As we've seen, the state doesn't matter, it's the change in state. Again, it can be tuned in USB or LSB, though USB is traditional.
A character space is two zeroes - 00. This is why all the characters end in 1.
The PSK31 idler consists of all zeroes, which flip the phase at the baud rate. This and the cosine shaping produce what is basically double-sideband suppressed-carrier emission (J2B). ITU refers to it as 60H0J2B, in the long international designators. This means suppressed-carrier modulation for automatic reception using a maximum channel width of 60 hertz.
The transmission starts with a distinctive railroad track pattern on the waterfall. Bursts of hand typing create something looking more like a DNA molecule. At the end of the transmission, it all collapses back into the single tone.
Receiving consists of syncing to the baud rate, which is determined from the signal, and sending the resulting data to a Viterbi decoder. There are no connections, and no error checks. Stations take turns sending, just like RTTY. Character hits print gibberish, again like RTTY. However, the copy is usually much better on HF, everything else being equal.
There's not much else to know. BPSK31 is very uncomplicated to the user. You click on a signal and copy comes out.
PSK31 immediately gave rise to a bewildering array of phase-shift keyed, character-based, half-duplex modes. If you've used MultiPSK you know what I'm talking about. Each new version has more little buttons and more funny noises than the last one. Since decode sync is determined from the signal, there's also an autodetect mode.
An early variant that should be in just about all PSK31 software is QPSK31. This stands for quaternary phase-shift keying. On the standard computer phase constellation display, you will see four points instead of two. This is done through the use of a second BPSK carrier shifted 90 degrees (in quadrature), driving a second receive demodulator.
While this should double throughput, the extra capacity is used for an error check and more robust decoding. The performance of this mode on degraded circuits is impressive, but at the cost of more bandwidth and a tuning precision challenging even modern solid-state radios.
Other BPSK and QPSK modes are at 10, 63, 125, and 250 baud. There's also PSK220F, a 220-baud mode well adapted to broadcasting. It is used by the Cuban numbers operation at times.
Saturday, May 31, 2008
Digital Mode of the Week: PSK31 (Part 1 - Varicode)
Varicode is a Huffman code for use in PSK31 narrow band teleprinting. PSK31 is a binary phase-shift keyed, 31.35-baud mode designed for direct keyboard-to-keyboard ham contacts. Varicode is integral to the overall concept that made PSK31 so well suited to ham radio, despite this low baud rate. In fact, it was the original name for the whole mode that was proposed in 1998 by its developer, an English ham named Peter Martinez (G3PLX).
Like many "major breakthroughs" in radio, the underlying concept has actually been around a while - in this case, since the Morse code. Morse speeds up transmission by making the more commonly used characters shorter, for example a single dit for E. Morse, like Huffman coding, lends itself to tree-shaped decoding algorithms that save a lot of time. Unlike with Baudot, logic can be designed (including in your brain) that bails out of the loop whenever it detects that a character is complete.
The basic Varicode character set is the same as 7-bit ASCII, but the bits aren't, and the framing is completely different. Throughput is a lot faster than if straight ASCII were being sent and everything else was equal. One consideration, however, is that efficiency goes down in languages other than English, or if the traffic is something other than plain lower case text. Either situation begins to deviate from the designed optimum.
The shortest character is the blank space (a single 1 bit), and second shortest is the lower case e (11). Note that all characters, including nulls, end in a 1. This is due to the technical characteristics of the transmission mode, which we'll talk about next week.
Here's the code. It should look familiar, except for the bits.
Dec . Hex .. Char ... Bit Code
....0 ... 00 ... NUL ... 1010101011
....1 ... 01 ... SOH ... 1011011011
....2 ... 02 ... STX ... 1011101101
....3 ... 03 ... ETX ... 1101110111
....4 ... 04 ... EOT ... 1011101011
....5 ... 05 ... ENQ ... 1101011111
....6 ... 06 ... ACK ... 1011101111
....7 ... 07 ... BEL .... 1011111101
....8 ... 08 ... BS ...... 1011111111
....9 ... 09 ... HT ...... 11101111
..10 ... 0A ... LF ...... 11101
..11 ... 0B ... VT ..... 1101101111
..12 ... 0C ... FF ...... 1011011101
..13 ... 0D ... CR ..... 11111
..14 ... 0E ... SO ...... 1101110101
..15 ... 0F ... SI ....... 1110101011
..16 ... 10 ... DLE ... 1011110111
..17 ... 11 ... DC1 ... 1011110101
..18 ... 12 ... DC2 ... 1110101101
..19 ... 13 ... DC3 ... 1110101111
..20 ... 14 ... DC4 ... 1101011011
..21 ... 15 ... NAK .. 1101101011
..22 ... 16 ... SYN ... 1101101101
..23 ... 17 ... ETB ... 1101010111
..24 ... 18 ... CAN .. 1101111011
..25 ... 19 ... EM ..... 1101111101
..26 ... 1A ... SUB .. 1110110111
..27 ... 1B ... ESC ... 1101010101
..28 ... 1C ... FS ..... 1101011101
..29 ... 1D ... GS .... 1110111011
..30 ... 1E ... RS ..... 1011111011
..31 ... 1F ... US ..... 1101111111
..32 ... 20 ... SP....... 1
..33 ... 21 ... ! ..... 111111111
..34 ... 22 ... " ..... 101011111
..35 ... 23 ... # .... 111110101
..36 ... 24 ... $ .... 111011011
..37 ... 25 ... % ... 1011010101
..38 ... 26 ... & .. 1010111011
..39 ... 27 ... ' ..... 101111111
..40 ... 28 ... ( .... 11111011
..41 ... 29 ... ) .... 11110111
..42 ... 2A ... * .. 101101111
..43 ... 2B ... +... 111011111
..44 ... 2C ... , .. 1110101
..45 ... 2D ... - .. 110101
..46 ... 2E ... . .. 1010111
..47 ... 2F ... / .. 110101111
..48 ... 30 ... 0... 10110111
..49 ... 31 ... 1... 10111101
..50 ... 32 ... 2... 11101101
..51 ... 33 ... 3... 11111111
..52 ... 34 ... 4... 101110111
..53 ... 35 ... 5... 101011011
..54 ... 36 ... 6... 101101011
..55 ... 37 ... 7... 110101101
..56 ... 38 ... 8... 110101011
..57 ... 39 ... 9... 110110111
..58 ... 3A ... : .. 11110101
..59 ... 3B ... ; .. 110111101
..60 ... 3C ... < .. 111101101
..61 ... 3D ... = .. 1010101
..62 ... 3E ... > .. 111010111
..63 ... 3F ... ? .. 1010101111
..64 ... 40 ... @ .. 1010111101
..65 ... 41 ... A... 1111101
..66 ... 42 ... B... 11101011
..67 ... 43 ... C... 10101101
..68 ... 44 ... D... 10110101
..69 ... 45 ... E... 1110111
..70 ... 46 ... F... 11011011
..71 ... 47 ... G... 11111101
..72 ... 48 ... H... 101010101
..73 ... 49 ... I... 1111111
..74 ... 4A ... J... 111111101
..75 ... 4B ... K... 101111101
..76 ... 4C ... L... 11010111
..77 ... 4D ... M... 10111011
..78 ... 4E ... N... 11011101
..79 ... 4F ... O... 10101011
..80 ... 50 ... P... 11010101
..81 ... 51 ... Q... 1111011101
..82 ... 52 ... R... 10101111
..83 ... 53 ... S... 1101111
..84 ... 54 ... T... 1101101
..85 ... 55 ... U... 101010111
..86 ... 56 ... V... 110110101
..87 ... 57 ... W... 101011101
..88 ... 58 ... X... 101110101
..89 ... 59 ... Y... 101111011
..90 ... 5A ... Z... 1010101101
..91 ... 5B ... [ .. 111110111
..92 ... 5C ... \ .. 111101111
..93 ... 5D ... ]... 111111011
..94 ... 5E ... ^ .. 1010111111
..95 ... 5F ... _ .. 101101101
..96 ... 60 ... ` .. 1011011111
..97 ... 61 ... a..... 1011
..98 ... 62 ... b..... 1011111
..99 ... 63 ... c..... 101111
100 ... 64 ... d..... 101101
101 ... 65 ... e..... 11
102 ... 66 ... f..... 111101
103 ... 67 ... g..... 1011011
104 ... 68 ... h..... 101011
105 ... 69 ... i...... 1101
106 ... 6A ... j..... 111101011
107 ... 6B ... k..... 10111111
108 ... 6C ... l..... 11011
109 ... 6D ... m... 111011
110 ... 6E ... n.... 1111
111 ... 6F ... o..... 111
112 ... 70 ... p..... 111111
113 ... 71 ... q..... 110111111
114 ... 72 ... r..... 10101
115 ... 73 ... s..... 10111
116 ... 74 ... t..... 101
117 ... 75 ... u..... 110111
118 ... 76 ... v..... 1111011
119 ... 77 ... w..... 1101011
120 ... 78 ... x..... 11011111
121 ... 79 ... y..... 1011101
122 ... 7A ... z..... 111010101
123 ... 7B ... {..... 1010110111
124 ... 7C ... |..... 110111011
125 ... 7D ... }.... 1010110101
126 ... 7E ... ~..... 1011010111
127 ... 7F .. DEL ... 1110110101
Like many "major breakthroughs" in radio, the underlying concept has actually been around a while - in this case, since the Morse code. Morse speeds up transmission by making the more commonly used characters shorter, for example a single dit for E. Morse, like Huffman coding, lends itself to tree-shaped decoding algorithms that save a lot of time. Unlike with Baudot, logic can be designed (including in your brain) that bails out of the loop whenever it detects that a character is complete.
The basic Varicode character set is the same as 7-bit ASCII, but the bits aren't, and the framing is completely different. Throughput is a lot faster than if straight ASCII were being sent and everything else was equal. One consideration, however, is that efficiency goes down in languages other than English, or if the traffic is something other than plain lower case text. Either situation begins to deviate from the designed optimum.
The shortest character is the blank space (a single 1 bit), and second shortest is the lower case e (11). Note that all characters, including nulls, end in a 1. This is due to the technical characteristics of the transmission mode, which we'll talk about next week.
Here's the code. It should look familiar, except for the bits.
Dec . Hex .. Char ... Bit Code
....0 ... 00 ... NUL ... 1010101011
....1 ... 01 ... SOH ... 1011011011
....2 ... 02 ... STX ... 1011101101
....3 ... 03 ... ETX ... 1101110111
....4 ... 04 ... EOT ... 1011101011
....5 ... 05 ... ENQ ... 1101011111
....6 ... 06 ... ACK ... 1011101111
....7 ... 07 ... BEL .... 1011111101
....8 ... 08 ... BS ...... 1011111111
....9 ... 09 ... HT ...... 11101111
..10 ... 0A ... LF ...... 11101
..11 ... 0B ... VT ..... 1101101111
..12 ... 0C ... FF ...... 1011011101
..13 ... 0D ... CR ..... 11111
..14 ... 0E ... SO ...... 1101110101
..15 ... 0F ... SI ....... 1110101011
..16 ... 10 ... DLE ... 1011110111
..17 ... 11 ... DC1 ... 1011110101
..18 ... 12 ... DC2 ... 1110101101
..19 ... 13 ... DC3 ... 1110101111
..20 ... 14 ... DC4 ... 1101011011
..21 ... 15 ... NAK .. 1101101011
..22 ... 16 ... SYN ... 1101101101
..23 ... 17 ... ETB ... 1101010111
..24 ... 18 ... CAN .. 1101111011
..25 ... 19 ... EM ..... 1101111101
..26 ... 1A ... SUB .. 1110110111
..27 ... 1B ... ESC ... 1101010101
..28 ... 1C ... FS ..... 1101011101
..29 ... 1D ... GS .... 1110111011
..30 ... 1E ... RS ..... 1011111011
..31 ... 1F ... US ..... 1101111111
..32 ... 20 ... SP....... 1
..33 ... 21 ... ! ..... 111111111
..34 ... 22 ... " ..... 101011111
..35 ... 23 ... # .... 111110101
..36 ... 24 ... $ .... 111011011
..37 ... 25 ... % ... 1011010101
..38 ... 26 ... & .. 1010111011
..39 ... 27 ... ' ..... 101111111
..40 ... 28 ... ( .... 11111011
..41 ... 29 ... ) .... 11110111
..42 ... 2A ... * .. 101101111
..43 ... 2B ... +... 111011111
..44 ... 2C ... , .. 1110101
..45 ... 2D ... - .. 110101
..46 ... 2E ... . .. 1010111
..47 ... 2F ... / .. 110101111
..48 ... 30 ... 0... 10110111
..49 ... 31 ... 1... 10111101
..50 ... 32 ... 2... 11101101
..51 ... 33 ... 3... 11111111
..52 ... 34 ... 4... 101110111
..53 ... 35 ... 5... 101011011
..54 ... 36 ... 6... 101101011
..55 ... 37 ... 7... 110101101
..56 ... 38 ... 8... 110101011
..57 ... 39 ... 9... 110110111
..58 ... 3A ... : .. 11110101
..59 ... 3B ... ; .. 110111101
..60 ... 3C ... < .. 111101101
..61 ... 3D ... = .. 1010101
..62 ... 3E ... > .. 111010111
..63 ... 3F ... ? .. 1010101111
..64 ... 40 ... @ .. 1010111101
..65 ... 41 ... A... 1111101
..66 ... 42 ... B... 11101011
..67 ... 43 ... C... 10101101
..68 ... 44 ... D... 10110101
..69 ... 45 ... E... 1110111
..70 ... 46 ... F... 11011011
..71 ... 47 ... G... 11111101
..72 ... 48 ... H... 101010101
..73 ... 49 ... I... 1111111
..74 ... 4A ... J... 111111101
..75 ... 4B ... K... 101111101
..76 ... 4C ... L... 11010111
..77 ... 4D ... M... 10111011
..78 ... 4E ... N... 11011101
..79 ... 4F ... O... 10101011
..80 ... 50 ... P... 11010101
..81 ... 51 ... Q... 1111011101
..82 ... 52 ... R... 10101111
..83 ... 53 ... S... 1101111
..84 ... 54 ... T... 1101101
..85 ... 55 ... U... 101010111
..86 ... 56 ... V... 110110101
..87 ... 57 ... W... 101011101
..88 ... 58 ... X... 101110101
..89 ... 59 ... Y... 101111011
..90 ... 5A ... Z... 1010101101
..91 ... 5B ... [ .. 111110111
..92 ... 5C ... \ .. 111101111
..93 ... 5D ... ]... 111111011
..94 ... 5E ... ^ .. 1010111111
..95 ... 5F ... _ .. 101101101
..96 ... 60 ... ` .. 1011011111
..97 ... 61 ... a..... 1011
..98 ... 62 ... b..... 1011111
..99 ... 63 ... c..... 101111
100 ... 64 ... d..... 101101
101 ... 65 ... e..... 11
102 ... 66 ... f..... 111101
103 ... 67 ... g..... 1011011
104 ... 68 ... h..... 101011
105 ... 69 ... i...... 1101
106 ... 6A ... j..... 111101011
107 ... 6B ... k..... 10111111
108 ... 6C ... l..... 11011
109 ... 6D ... m... 111011
110 ... 6E ... n.... 1111
111 ... 6F ... o..... 111
112 ... 70 ... p..... 111111
113 ... 71 ... q..... 110111111
114 ... 72 ... r..... 10101
115 ... 73 ... s..... 10111
116 ... 74 ... t..... 101
117 ... 75 ... u..... 110111
118 ... 76 ... v..... 1111011
119 ... 77 ... w..... 1101011
120 ... 78 ... x..... 11011111
121 ... 79 ... y..... 1011101
122 ... 7A ... z..... 111010101
123 ... 7B ... {..... 1010110111
124 ... 7C ... |..... 110111011
125 ... 7D ... }.... 1010110101
126 ... 7E ... ~..... 1011010111
127 ... 7F .. DEL ... 1110110101
STS-124 Countdown Continues
Launch is still scheduled for around 2104 UTC today (Saturday). The astronauts are presently entering the spacecraft.
Allan Stern has heard Booster Recovery Vessel traffic on 10780 and 5711 kHz.
Allan Stern has heard Booster Recovery Vessel traffic on 10780 and 5711 kHz.
Wednesday, May 28, 2008
STS-124 Tentative Launch Is Saturday
Shuttle Discovery's STS-124 mission to the International Space Station is scheduled to lift off at 5:02 p.m. EDT [2102 UTC] on Saturday, May 31.
Astronauts arrived at KSC this morning.
NASA will provide continuous online updates, including a webcast and a blog on the STS-124 mission at:
http://www.nasa.gov/shuttle
On launch day, a blog will update the countdown beginning at noon. Originating from NASA's Kennedy Space Center, the blog is the definitive Internet source for information leading up to launch. During the mission, visitors to NASA's shuttle Web site can read about the crew's progress and watch the spacewalks live. As Discovery's flight wraps up, NASA will offer a blog detailing the spacecraft's return to Earth.
Detailed lists of countdown milestones, news briefing times and participants, and hours of operation for Kennedy's news center and media credentialing office are available at:
http://www.nasa.gov/mission_pages/shuttle/news
For NASA TV streaming video, scheduling and downlink information, visit:
http://www.nasa.gov/ntv
Astronauts arrived at KSC this morning.
NASA will provide continuous online updates, including a webcast and a blog on the STS-124 mission at:
http://www.nasa.gov/shuttle
On launch day, a blog will update the countdown beginning at noon. Originating from NASA's Kennedy Space Center, the blog is the definitive Internet source for information leading up to launch. During the mission, visitors to NASA's shuttle Web site can read about the crew's progress and watch the spacewalks live. As Discovery's flight wraps up, NASA will offer a blog detailing the spacecraft's return to Earth.
Detailed lists of countdown milestones, news briefing times and participants, and hours of operation for Kennedy's news center and media credentialing office are available at:
http://www.nasa.gov/mission_pages/shuttle/news
For NASA TV streaming video, scheduling and downlink information, visit:
http://www.nasa.gov/ntv
Sunday, May 25, 2008
Digital Mode of the Week: HFDL
HFDL stands for High-Frequency Data Link. It is the HF band portion of a comprehensive, global, air-ground, communications system that also uses VHF and satellite. The ACARS ( Aircraft Communications Addressing and Reporting System) is another part of all this. Most people associate ACARS with VHF, but the HFDL protocol can carry it as well.
The HFDL standard is ARINC Report 635-3 (HF Data Link Protocols), which can be ordered from the company, Aeronautical Radio Inc, for a price. ARINC is a private company, formerly owned by the airlines, but now contracting with them for communication services.
Like packet radio, HFDL has layers. These are physical, link, and subnetwork. The subnetwork layer isn't important for receiving, since we're just randomly decoding everything on a frequency.
The physical layer is, once again, the actual transmission of data over the radio. HFDL is a single-tone, phase-shift keyed, text-based, error-checking mode with a baseband audio carrier frequency of 1440 Hz. It is tuned in USB, and the 1440 Hz center is critical for decoding. LSB works too, but the dial frequencies won't match the ones in the ARINC database.
Each burst begins with the unmodulated 1440-Hz tone, so that the decoder's automatic frequency control can lock on. This is the scary-sounding "frequency error" that is output by the decoder. Errors within 50 Hz or so can be ignored. This beeping, followed by hiss, is what the mode sounds like.
The symbol speed is fixed at 1800 baud, but the data rate is determined by the exact modulation used. BPSK is 300 bps, QPSK is 600, and 8PSK is 1200 or 1800. 300 is by far the most common, though I've heard it go up to 1200. Tuning error, modulation type, and signal quality are best viewed on a phase constellation display like the one in the PC-HFDL program.
Frequencies are stored in a numbered database, called a system table, which is sent by ARINC to all stations. A few times a year, the table is replaced by a new one with a higher number. The resulting mismatch causes aircraft software to request an update, which we receive too. At least one decoding program (again PC-HFDL) will grab these for its own use, if you're lucky to hear one. Afterward, the frequencies show up in kHz, which is extremely convenient. Otherwise, there are ways to update PC-HFDL manually with system tables found online.
Old databases aren't useless. The frequencies always come from the same pool, and never change that much.
Ground stations pick 2-3 frequencies from the table depending on propagation. This may change every few hours. The frequencies being used by the entire network are sent, two stations at a time, in the "squitter." (Squitter in air comm jargon is an unsolicited information transmission. More on these soon.)
Aircraft can choose frequencies, or even ground stations. If reception exists, they can also switch to satellite or VHF. The comm status is passed to the ground station. All this is automatic, so the crew can just get on with flying the airplane.
Transmission types are uplinks (ground-air), downlinks (air-ground), and the aforementioned squitters. A squitter is always sent every 32 seconds by the ground. It contains various network maintenance data, including all the frequencies (if you wait long enough). It's also a quick propagation check, because you're never more than half a minute from a ground transmission coming from a known location. Of course, aircraft may be heard even if the squitters are inaudible, and vice versa.
HFDL uses a simple form of time-division multiplex. The entire 32-second cycle is divided into 13 numbered slots of 2.5 seconds each. Slot 0 is always the squitter, leaving 1-12 for up- and downlinks. Databursts always occupy all of one slot, though the various overheads of the physical layer reduce the actual transmission of data to 1.8 seconds. Sometimes an uplink with an embedded ACARS message might require a double-length transmission using two slots.
The network assigns the use of these slots, keeping stations from transmitting at once. Assignments are made by ID, a temporary hexadecimal number given each aircraft at logon.
The use of condensed message formats and lookup tables makes HFDL extremely efficient in its use of air time. It's amazing how much can be crammed into a 2-second burst. Most decoders have a "verbose" mode which will output everything. Hundreds of lines with every kind of count and measurement you can think of will scroll madly up your screen, filling your buffer at a merry rate.
Really long ACARS messages, like airport arrival information (ATIS), can be sent in numbered packets (same as on VHF). Otherwise the communication makes use of standard formatted blocks called Protocol Data Units (PDU). This gets geeky in a hurry. Rather than write a 2000-word blog entry, I'll just list them:
SPDU
Squitter Protocol Data Unit
Frequencies and slot assignments, plus network maintenance data
PDU (PREAM)
Preamble Data Unit
Basic negotiation of connection - frequency error, station ID, bit rate, etc
BDU
Basic Data Unit
The smallest data block, from which LPDU are built
LPDU
Link Protocol Data Unit
Larger structure, which in turn makes up the largest ones
MPDU
Media Access Protocol Data Unit
Several LPDU concerning login, aircraft ID, and the ACARS message, if any
HFNPDU
High-Frequency Network Protocol Data Unit
Several LPDU, containing all manner of data, most for network maintenance. The most useful to us is HFNPDU PERFORMANCE, which will usually contain the flight number and GPS position of the aircraft.
Here are the ARINC ground stations. Note that some numbers are skipped:
1 San Francisco, CA
2 Molokai, HI
3 Reykjavik, Iceland
4 New York, NY
5 Auckland, NZ
6 Hat Yai, Thailand
7 Shannon, Ireland
8 Johannesburg, S. Africa
9 Barrow, AK
13 Santa Cruz, Bolivia
14 Krasnoyarsk, Russia
15 Al Muharraq, Bahrain
16 Guam
17 Canarias (Canary Islands)
The HFDL standard is ARINC Report 635-3 (HF Data Link Protocols), which can be ordered from the company, Aeronautical Radio Inc, for a price. ARINC is a private company, formerly owned by the airlines, but now contracting with them for communication services.
Like packet radio, HFDL has layers. These are physical, link, and subnetwork. The subnetwork layer isn't important for receiving, since we're just randomly decoding everything on a frequency.
The physical layer is, once again, the actual transmission of data over the radio. HFDL is a single-tone, phase-shift keyed, text-based, error-checking mode with a baseband audio carrier frequency of 1440 Hz. It is tuned in USB, and the 1440 Hz center is critical for decoding. LSB works too, but the dial frequencies won't match the ones in the ARINC database.
Each burst begins with the unmodulated 1440-Hz tone, so that the decoder's automatic frequency control can lock on. This is the scary-sounding "frequency error" that is output by the decoder. Errors within 50 Hz or so can be ignored. This beeping, followed by hiss, is what the mode sounds like.
The symbol speed is fixed at 1800 baud, but the data rate is determined by the exact modulation used. BPSK is 300 bps, QPSK is 600, and 8PSK is 1200 or 1800. 300 is by far the most common, though I've heard it go up to 1200. Tuning error, modulation type, and signal quality are best viewed on a phase constellation display like the one in the PC-HFDL program.
Frequencies are stored in a numbered database, called a system table, which is sent by ARINC to all stations. A few times a year, the table is replaced by a new one with a higher number. The resulting mismatch causes aircraft software to request an update, which we receive too. At least one decoding program (again PC-HFDL) will grab these for its own use, if you're lucky to hear one. Afterward, the frequencies show up in kHz, which is extremely convenient. Otherwise, there are ways to update PC-HFDL manually with system tables found online.
Old databases aren't useless. The frequencies always come from the same pool, and never change that much.
Ground stations pick 2-3 frequencies from the table depending on propagation. This may change every few hours. The frequencies being used by the entire network are sent, two stations at a time, in the "squitter." (Squitter in air comm jargon is an unsolicited information transmission. More on these soon.)
Aircraft can choose frequencies, or even ground stations. If reception exists, they can also switch to satellite or VHF. The comm status is passed to the ground station. All this is automatic, so the crew can just get on with flying the airplane.
Transmission types are uplinks (ground-air), downlinks (air-ground), and the aforementioned squitters. A squitter is always sent every 32 seconds by the ground. It contains various network maintenance data, including all the frequencies (if you wait long enough). It's also a quick propagation check, because you're never more than half a minute from a ground transmission coming from a known location. Of course, aircraft may be heard even if the squitters are inaudible, and vice versa.
HFDL uses a simple form of time-division multiplex. The entire 32-second cycle is divided into 13 numbered slots of 2.5 seconds each. Slot 0 is always the squitter, leaving 1-12 for up- and downlinks. Databursts always occupy all of one slot, though the various overheads of the physical layer reduce the actual transmission of data to 1.8 seconds. Sometimes an uplink with an embedded ACARS message might require a double-length transmission using two slots.
The network assigns the use of these slots, keeping stations from transmitting at once. Assignments are made by ID, a temporary hexadecimal number given each aircraft at logon.
The use of condensed message formats and lookup tables makes HFDL extremely efficient in its use of air time. It's amazing how much can be crammed into a 2-second burst. Most decoders have a "verbose" mode which will output everything. Hundreds of lines with every kind of count and measurement you can think of will scroll madly up your screen, filling your buffer at a merry rate.
Really long ACARS messages, like airport arrival information (ATIS), can be sent in numbered packets (same as on VHF). Otherwise the communication makes use of standard formatted blocks called Protocol Data Units (PDU). This gets geeky in a hurry. Rather than write a 2000-word blog entry, I'll just list them:
SPDU
Squitter Protocol Data Unit
Frequencies and slot assignments, plus network maintenance data
PDU (PREAM)
Preamble Data Unit
Basic negotiation of connection - frequency error, station ID, bit rate, etc
BDU
Basic Data Unit
The smallest data block, from which LPDU are built
LPDU
Link Protocol Data Unit
Larger structure, which in turn makes up the largest ones
MPDU
Media Access Protocol Data Unit
Several LPDU concerning login, aircraft ID, and the ACARS message, if any
HFNPDU
High-Frequency Network Protocol Data Unit
Several LPDU, containing all manner of data, most for network maintenance. The most useful to us is HFNPDU PERFORMANCE, which will usually contain the flight number and GPS position of the aircraft.
Here are the ARINC ground stations. Note that some numbers are skipped:
1 San Francisco, CA
2 Molokai, HI
3 Reykjavik, Iceland
4 New York, NY
5 Auckland, NZ
6 Hat Yai, Thailand
7 Shannon, Ireland
8 Johannesburg, S. Africa
9 Barrow, AK
13 Santa Cruz, Bolivia
14 Krasnoyarsk, Russia
15 Al Muharraq, Bahrain
16 Guam
17 Canarias (Canary Islands)
Saturday, May 24, 2008
Interesting RTTY Message from KSM 24 May 08
KSM is the commercial station at the Maritime Radio Historical Society, Pt. Reyes, CA (at the old RCA/MCI maritime and point to point site). In cooperation with the Comm Center group on Yahoo!, which is comprised of former or retired military communicators, it broadcast several RTTY/RATT messages in standard military form.
Here's one of the most interesting ones. All net discipline is exactly as received. The "?" character was used in the message to replace ones that aren't in ITA2. Any format changes, such as stripping leading blanks, were done by Blogger, not me:
VV HNA033
RR RUWMKSM
DE RUMLNHA 0033 1410200
ZNR UUUUU
R 200131Z MAY 08
FM COMMCENTER AT YAHOOGROUPS.COM //NNN7DXB//
TO KSM MARINE RADIO SAN FRANCISCO CA //KSM BCST//
BT
UNCLAS
SUBJ: ACP-127 FORMATTED MESSAGE
REF: ACP-127 TAPE RELAY INSTRUCTIONS ( )
1. THIS IS AN EXAMPLE OF A MILITARY MESSAGE FORMATTED IN
THE ACP-127 TELETYPE TAPE RELAY FORMAT THAT WAS IN USE
IN THE US MILITARY PRIOR TO THE MID-1970S. DURING THE 1970S,
THE MILITARY TELETYPE TAPE RELAY SYSTEM, ALSO KNOWN AS
THE ?TORN TAPE RELAY SYSTEM? WAS SLOWLY REPLACED BY THE NEWER
AND FASTER AUTOMATIC DIGITIAL NETWORK, OR ?AUTODIN?.
2. AUTODIN WAS A HIGH-SPEED, HIGH CAPACITY, COMPUTER CONTROLLED
?SUPER TELETYPE? SYSTEM THAT WAS ALSO CAPABLE OF HANDLING
DATA TRAFFIC IN IBM PUNCHED CARD FORM (HOLLERITH CODE), AND
MAGNETIC MEDIA. IT RELIED ON SERVOS AND TAPE DRIVES, AND LATER,
WAS UPGRADED WITH WHAT WE NOW REFER TO AS HARD DRIVES
THAT WERE ABOUT THE SIZE OF WASHING MACHINES. SOME OF
THE MAIN BRAINS IN THE AUTODIN SYSTEM WERE RCA SPECTRE 70
PAGE 2 RUMLNHA0033 UNCLAS
MAIN FRAME COMPUTERS. MOST ARMY AUTODIN FACILITIES WERE
MAINTAINED BY EITHER PHILCO-FORD OR WESTERN UNION UNDER
DOD CONTRACT. AUTODIN ITSELF WAS FINALLY REPLACED ON
SEPTEMBER 30, 2003 BY A NEW MEDIUM CALLED THE DEFENSE
MESSAGING SYSTEM, OR ?DMS?. DMS OFFERS MORE CAPACITY THAN
DID AUTODIN. IT PERMITS ATTACHMENTS, GRAPHICS, MAPS, MAP
OVERLAYS, LETTERS AND NON-MESSAGE CORRESPONDENCE, FILES,
AND EMAIL TRAFFIC TO BE TRANSMITTED IN A SINGLE SECURE SYSTEM
THAT IS WORLDWIDE IN SCOPE AND OPERATION.
3. ACP-127 PROCEDURES HOWEVER, DIDN"T GO AWAY. MOST US
MILITARY TACTICAL CIRCUITS STILL USED ACP-127 FORMATS UNTIL
THE LATE 1980S, UNTIL THE AUTODIN SYSTEM WAS FINALLY
INTEGRATED IN THE FIELD UNITS. NATO UNITS CONTINUED TO USE
ACP-127 FORMATS, SINCE NONE OF THEIR EQUIPMENTS OR SYSTEMS
WERE COMPATIBLE WITH THE US COMPUTERIZED FORMAT. SYSTEM
COMPATIBILITY IN THOSE DAYS WAS CALLED ?INTEROPERABILITY?.
EVEN TODAY, ACP-127 FORMATS CAN STILL BE FOUND IN SOME
NATO COUNTRIES WHERE INTEROPERABILITY ISSUES CONTINUE
TO PERSIST.
4. TRANSMITTED AS AN INFORMATIONAL SERVICE BY THE
PAGE 3 RUMLNHA0033 UNCLAS
COMMCENTER AT YAHOOGROUPS.COM GROUP. ALL MATERIAL
APPEARING HEREIN IS IN THE PUBLIC DOMAIN.
5. SERVICE AND SUPPORT TO THE TROOPS FROM ONE OF THE
US ARMY"S FINEST COMMUNICATIONS OPERATIONS CHIEFS OF
THE 1ST INFANTRY DIVISION (FORWARD), FORMERLY LOCATED
A COOKE BARRACKS, GOEPPINGEN, NEAR STUTTGART, GERMANY.
BT
0033
NNNN
Here's one of the most interesting ones. All net discipline is exactly as received. The "?" character was used in the message to replace ones that aren't in ITA2. Any format changes, such as stripping leading blanks, were done by Blogger, not me:
VV HNA033
RR RUWMKSM
DE RUMLNHA 0033 1410200
ZNR UUUUU
R 200131Z MAY 08
FM COMMCENTER AT YAHOOGROUPS.COM //NNN7DXB//
TO KSM MARINE RADIO SAN FRANCISCO CA //KSM BCST//
BT
UNCLAS
SUBJ: ACP-127 FORMATTED MESSAGE
REF: ACP-127 TAPE RELAY INSTRUCTIONS ( )
1. THIS IS AN EXAMPLE OF A MILITARY MESSAGE FORMATTED IN
THE ACP-127 TELETYPE TAPE RELAY FORMAT THAT WAS IN USE
IN THE US MILITARY PRIOR TO THE MID-1970S. DURING THE 1970S,
THE MILITARY TELETYPE TAPE RELAY SYSTEM, ALSO KNOWN AS
THE ?TORN TAPE RELAY SYSTEM? WAS SLOWLY REPLACED BY THE NEWER
AND FASTER AUTOMATIC DIGITIAL NETWORK, OR ?AUTODIN?.
2. AUTODIN WAS A HIGH-SPEED, HIGH CAPACITY, COMPUTER CONTROLLED
?SUPER TELETYPE? SYSTEM THAT WAS ALSO CAPABLE OF HANDLING
DATA TRAFFIC IN IBM PUNCHED CARD FORM (HOLLERITH CODE), AND
MAGNETIC MEDIA. IT RELIED ON SERVOS AND TAPE DRIVES, AND LATER,
WAS UPGRADED WITH WHAT WE NOW REFER TO AS HARD DRIVES
THAT WERE ABOUT THE SIZE OF WASHING MACHINES. SOME OF
THE MAIN BRAINS IN THE AUTODIN SYSTEM WERE RCA SPECTRE 70
PAGE 2 RUMLNHA0033 UNCLAS
MAIN FRAME COMPUTERS. MOST ARMY AUTODIN FACILITIES WERE
MAINTAINED BY EITHER PHILCO-FORD OR WESTERN UNION UNDER
DOD CONTRACT. AUTODIN ITSELF WAS FINALLY REPLACED ON
SEPTEMBER 30, 2003 BY A NEW MEDIUM CALLED THE DEFENSE
MESSAGING SYSTEM, OR ?DMS?. DMS OFFERS MORE CAPACITY THAN
DID AUTODIN. IT PERMITS ATTACHMENTS, GRAPHICS, MAPS, MAP
OVERLAYS, LETTERS AND NON-MESSAGE CORRESPONDENCE, FILES,
AND EMAIL TRAFFIC TO BE TRANSMITTED IN A SINGLE SECURE SYSTEM
THAT IS WORLDWIDE IN SCOPE AND OPERATION.
3. ACP-127 PROCEDURES HOWEVER, DIDN"T GO AWAY. MOST US
MILITARY TACTICAL CIRCUITS STILL USED ACP-127 FORMATS UNTIL
THE LATE 1980S, UNTIL THE AUTODIN SYSTEM WAS FINALLY
INTEGRATED IN THE FIELD UNITS. NATO UNITS CONTINUED TO USE
ACP-127 FORMATS, SINCE NONE OF THEIR EQUIPMENTS OR SYSTEMS
WERE COMPATIBLE WITH THE US COMPUTERIZED FORMAT. SYSTEM
COMPATIBILITY IN THOSE DAYS WAS CALLED ?INTEROPERABILITY?.
EVEN TODAY, ACP-127 FORMATS CAN STILL BE FOUND IN SOME
NATO COUNTRIES WHERE INTEROPERABILITY ISSUES CONTINUE
TO PERSIST.
4. TRANSMITTED AS AN INFORMATIONAL SERVICE BY THE
PAGE 3 RUMLNHA0033 UNCLAS
COMMCENTER AT YAHOOGROUPS.COM GROUP. ALL MATERIAL
APPEARING HEREIN IS IN THE PUBLIC DOMAIN.
5. SERVICE AND SUPPORT TO THE TROOPS FROM ONE OF THE
US ARMY"S FINEST COMMUNICATIONS OPERATIONS CHIEFS OF
THE 1ST INFANTRY DIVISION (FORWARD), FORMERLY LOCATED
A COOKE BARRACKS, GOEPPINGEN, NEAR STUTTGART, GERMANY.
BT
0033
NNNN
Monday, May 19, 2008
Digital Mode of the Week: PACTOR
PACTOR® (from Latin "the mediator," also a possible play on PACket plus amTOR) was developed by German hams in the early 1990s. It was originally intended to deal with the limitations of packet radio and AMTOR over noisy and fading HF circuits. It has become something of a de facto standard for HF e-mail systems, not only in amateur bands but also in commercial networks used by ships at sea and by nongovernmental organizations working in isolated areas.
PACTOR was originally based on the clever idea of using the good features of HF packet (robust error checking) and of AMTOR/SITOR (tight sync, short packet lengths), while eliminating the bad ones. The data bursts are longer than SITOR's, greatly reducing the timing demands on equipment. The protocol is better suited to HF than AX.25 packet, meaning fewer retries. Much of the time, PACTOR outperforms both modes in real-world band conditions.
The original mode is called PACTOR-I (Roman numeral one). The company has been speeding it up and adding features ever since, to the point where PACTOR-I is now rather slow and primitive by comparison.
PACTOR-I is a half-duplex, synchronous, ARQ mode which uses connections. The initiating station operates in "master" mode, while the called station is the "slave." Stations then take turns as information sending and receiving stations. The receiving station does a Cyclic Redundancy Check (CRC) on the packets, and transmits a brief ACK/NAK Control Signal (CS). In order to speed things up, a system called "memory ARQ" is used to compare packets and reduce repetition. In the original SCS equipment, this feature used an extremely clever analog algorithm.
There is also a PACTOR-I FEC mode. This does not use connections, but something resembling the "unproto" mode in packet. Frames are repeated and padded out with character 21 if nothing is in the send buffer.
PACTOR-I packet lengths are 96 bits in the slow mode (100 baud) and 192 at 200 baud. The modems are able to choose the appropriate data rate based on error responses from the receiver. PACTOR uses online data compression to further speed up throughput. Text is ASCII using Huffman coding (which prints as garbage unless decoded), falling back to straight ASCII when necessary or for calling.
PACTOR-I modulation is frequency-shift keying (FSK/AFSK), 200-Hertz shift. Like packet, the bits are in the state transitions, so it can be successfully tuned in either USB or LSB without changing polarity. For this reason, amateur mailboxes often list PACTOR frequencies by their center of intelligence, between the two original FSK tones, which then are +/- 100 Hz. LSB dial/window reading will then be the center frequency plus the audio center of your modem or software. On USB, you subtract the audio center.
PACTOR-I has been released for use in any 3rd party products, including modems and multimode sound card programs. It can be considered a standard. Everything else, however, remains completely proprietary to SCS, the German company started by PACTOR's inventors, or its licensees. The company has also worked with large commercial networks such as Globe Wireless to adapt PACTOR into even more proprietary modes.
SCS modems are high-end products for professional use, and they are priced accordingly. There has been some criticism from hams that these prices are a bit out of reach for amateurs. SCS has answered with a simplified PACTOR modem, the PTC-IIex, that lists for "only" 614 Euros as opposed to 1025 Euros for the full-featured version. Of course, either of these prices is a steal compared to the staggeringly expensive WAVECOM and HOKA multimode packages that will do all PACTOR's modes.
Out in the real world, PACTOR-I is used mostly for calling. Some people are still reporting traffic in it, but otherwise you'll be able to tell it's PACTOR and grab a callsign or two, then things will get weird in a hurry as the modems adapt. They'll start to switch quickly through a truly bewildering number of highly advanced modes that remain available only in boxes made or licensed by SCS.
PACTOR-II adds several more compression and coding features, and switches the modem to differential phase-shift keying (DPSK) to save spectrum. The sound changes from the well known lazy brrrrrrp brrrrrrp brrrrrrp to various hisses and buzzes usually otherwise heard in advanced military modes. Throughput increases from 100/200 baud to a best case 1200 bits/sec using compression.
The current hot setup is PACTOR-III, which adds yet more features to the firmware in existing SCS modems. Users can try these features for 20 connects, then a license is required. This one goes at a screaming best case throughput of 5200 bits/sec, though in doing so it becomes very wide indeed (2.4 kHz), with 18 tones and a physical bitrate of 3600/sec.
Here's a list of PACTOR modulations:
PACTOR-I:
FSK, 200 Hz, 100/200 baud
PACTOR-II (uncompressed)
2 tone DBPSK, 200 b/s physical, 100 b/s throughput
2 tone DQPSK, 400 b/s, 200
2 tone 8-DPSK, 600 b/s, 400
2 tone 16-DPSK, 800 b/s, 700
PACTOR-III (uncompressed)
2 tones, 200 b/s physical, 76.8 net data rate
6 tones, 600 b/s, 247.5
14 tones, 1400 b/s, 588.8
16 tones, 3200 b/s, 2039.5
18 tones, 3600 b/s, 2722.1
Pactor-III also has many submodes depending on various combinations of tones and DBPSK vs DQPSK.
In all modems, the maximum speed level can be set by the user.
--
Legal note: PACTOR® is a registered trademark of SCS, Germany.
http://www.scs-ptc.com/
PACTOR was originally based on the clever idea of using the good features of HF packet (robust error checking) and of AMTOR/SITOR (tight sync, short packet lengths), while eliminating the bad ones. The data bursts are longer than SITOR's, greatly reducing the timing demands on equipment. The protocol is better suited to HF than AX.25 packet, meaning fewer retries. Much of the time, PACTOR outperforms both modes in real-world band conditions.
The original mode is called PACTOR-I (Roman numeral one). The company has been speeding it up and adding features ever since, to the point where PACTOR-I is now rather slow and primitive by comparison.
PACTOR-I is a half-duplex, synchronous, ARQ mode which uses connections. The initiating station operates in "master" mode, while the called station is the "slave." Stations then take turns as information sending and receiving stations. The receiving station does a Cyclic Redundancy Check (CRC) on the packets, and transmits a brief ACK/NAK Control Signal (CS). In order to speed things up, a system called "memory ARQ" is used to compare packets and reduce repetition. In the original SCS equipment, this feature used an extremely clever analog algorithm.
There is also a PACTOR-I FEC mode. This does not use connections, but something resembling the "unproto" mode in packet. Frames are repeated and padded out with character 21 if nothing is in the send buffer.
PACTOR-I packet lengths are 96 bits in the slow mode (100 baud) and 192 at 200 baud. The modems are able to choose the appropriate data rate based on error responses from the receiver. PACTOR uses online data compression to further speed up throughput. Text is ASCII using Huffman coding (which prints as garbage unless decoded), falling back to straight ASCII when necessary or for calling.
PACTOR-I modulation is frequency-shift keying (FSK/AFSK), 200-Hertz shift. Like packet, the bits are in the state transitions, so it can be successfully tuned in either USB or LSB without changing polarity. For this reason, amateur mailboxes often list PACTOR frequencies by their center of intelligence, between the two original FSK tones, which then are +/- 100 Hz. LSB dial/window reading will then be the center frequency plus the audio center of your modem or software. On USB, you subtract the audio center.
PACTOR-I has been released for use in any 3rd party products, including modems and multimode sound card programs. It can be considered a standard. Everything else, however, remains completely proprietary to SCS, the German company started by PACTOR's inventors, or its licensees. The company has also worked with large commercial networks such as Globe Wireless to adapt PACTOR into even more proprietary modes.
SCS modems are high-end products for professional use, and they are priced accordingly. There has been some criticism from hams that these prices are a bit out of reach for amateurs. SCS has answered with a simplified PACTOR modem, the PTC-IIex, that lists for "only" 614 Euros as opposed to 1025 Euros for the full-featured version. Of course, either of these prices is a steal compared to the staggeringly expensive WAVECOM and HOKA multimode packages that will do all PACTOR's modes.
Out in the real world, PACTOR-I is used mostly for calling. Some people are still reporting traffic in it, but otherwise you'll be able to tell it's PACTOR and grab a callsign or two, then things will get weird in a hurry as the modems adapt. They'll start to switch quickly through a truly bewildering number of highly advanced modes that remain available only in boxes made or licensed by SCS.
PACTOR-II adds several more compression and coding features, and switches the modem to differential phase-shift keying (DPSK) to save spectrum. The sound changes from the well known lazy brrrrrrp brrrrrrp brrrrrrp to various hisses and buzzes usually otherwise heard in advanced military modes. Throughput increases from 100/200 baud to a best case 1200 bits/sec using compression.
The current hot setup is PACTOR-III, which adds yet more features to the firmware in existing SCS modems. Users can try these features for 20 connects, then a license is required. This one goes at a screaming best case throughput of 5200 bits/sec, though in doing so it becomes very wide indeed (2.4 kHz), with 18 tones and a physical bitrate of 3600/sec.
Here's a list of PACTOR modulations:
PACTOR-I:
FSK, 200 Hz, 100/200 baud
PACTOR-II (uncompressed)
2 tone DBPSK, 200 b/s physical, 100 b/s throughput
2 tone DQPSK, 400 b/s, 200
2 tone 8-DPSK, 600 b/s, 400
2 tone 16-DPSK, 800 b/s, 700
PACTOR-III (uncompressed)
2 tones, 200 b/s physical, 76.8 net data rate
6 tones, 600 b/s, 247.5
14 tones, 1400 b/s, 588.8
16 tones, 3200 b/s, 2039.5
18 tones, 3600 b/s, 2722.1
Pactor-III also has many submodes depending on various combinations of tones and DBPSK vs DQPSK.
In all modems, the maximum speed level can be set by the user.
--
Legal note: PACTOR® is a registered trademark of SCS, Germany.
http://www.scs-ptc.com/
Thursday, May 08, 2008
FCC Denies Miller Digital Bandwidth Petition
In a Report and Order in the matter of RM-11392, the FCC has denied a rule making petition by amateur Mark Miller regarding bandwidth and frequencies used for digital modes, especially by automatically controlled stations.
Miller's argument was that the adoption of wideband data and image transmission by new generations of computer-oriented hams would clog the subbands now being used for such older modes as RTTY. He asked for tighter limits on these, more or less rolling back the FCC rules to before 2006. He noted his awareness that this would also effectively ban Pactor-III and ALE, but that was the price of good spectrum management.
Most of the 650 comments were negative, and Miller's filing had been widely derogated as the "digital stone age petition." The FCC agreed that he had not made a good case that rule changes were necessary.
Miller's argument was that the adoption of wideband data and image transmission by new generations of computer-oriented hams would clog the subbands now being used for such older modes as RTTY. He asked for tighter limits on these, more or less rolling back the FCC rules to before 2006. He noted his awareness that this would also effectively ban Pactor-III and ALE, but that was the price of good spectrum management.
Most of the 650 comments were negative, and Miller's filing had been widely derogated as the "digital stone age petition." The FCC agreed that he had not made a good case that rule changes were necessary.
Armed Forces Day SECDEF Message This Saturday
From Army MARS:
SECRETARY OF DEFENSE MESSAGE TEST VIA DIGITAL MODES.
The Secretary of Defense message will be transmitted via digital modes including RTTY, PACTOR, AMTOR, PSK-31, MFSK and MT63 from the stations listed below, including frequencies, mode, and date/time in Zulu (UTC). All frequencies are listed for center of intelligence. Offset as appropriate for your TNC. (Note: Not all stations may necessarily operate on all the frequencies listed, depending on propagation and available equipment.)
Army Stations
STATION: AAZ (HQ Army MARS Gateway, Fort Huachuca, Arizona)
6988.0 kHz
RTTY 11 May 0110Z
PACTOR FEC 11 May 0130Z
MT63 11 May 0220Z
PSK-31 11 May 0250Z
14402.0 kHz
RTTY 11 May 0110Z
PACTOR FEC 11 May 0130Z
MT63 11 May 0220Z
PSK-31 11 May 0250Z
STATION: WAR (Pentagon ARC/MARS Station, Arlington, Virginia)
6988.0 kHz
RTTY 10 May 1700Z
RTTY 10 May 2300Z
MT63 10 May 1715Z
MT63 10 May 2315Z
14440.0 kHz
PACTOR FEC 10 May 1730Z
PACTOR FEC 10 May 2330Z
Olivia 10 May 1745Z
Olivia 10 May 2345Z
Stations copying the Secretary of Defense message transmitted from AAZ/WAR should send their entries to Armed Forces Day Celebration, Commander NETCOM/9th ASC, Attn: NETC-OPE-MA (MARS) (31), Fort Huachuca, AZ 85613-5000.
Air Force Stations
STATION: AIR-2 (Scott Air Force Base)
7831.1 kHz
RTTY 10 May/1930Z
PACTOR 10 May/2000Z
MT63 10 May/2030Z
MFSK 10 May/2100Z
14877.1 kHz
RTTY 10 May/2130Z
PACTOR 10 May/2200Z
MT63 10 May/2230Z
MFSK 10 May/2300Z
Navy/Marine Corps Stations
STATION: NAV (HQ NAVMARCORMARS Radio Station, WILLIAMSBURG, VA)
7346.5 kHz
RTTY 75 baud 10 May/2340Z
AMTOR FEC 11 May/0010Z
MT63 11 May/0040Z
14480.0 kHz
RTTY 75 baud 10 May/2340Z
AMTOR FEC 11 May/0010Z
MT63 11 May/0040Z
STATION: NAV3 (NAVMARCORMARS Radio Station, CORPUS CHRISTI, TX)
7393.0 kHz
RTTY 10 May/2340Z
AMTOR FEC 11 May/0010Z
MT63 11 May/0040Z
13975.5 kHz
RTTY 10 May/2340Z
AMTOR FEC 11 May/0010Z
MT63 11 May/0040Z
STATION: NAV4 (NAVMARCORMARS Radio Station, GREAT LAKES, IL)
7375.0 kHz
RTTY 11 May/0240Z
AMTOR FEC 11 May/0310Z
MT63 11 May/0340Z
14468.5 kHz
RTTY 11 May/0240Z
AMTOR FEC 11 May/0310Z
MT63 11 May/0340Z
STATION: NBL (NAVMARCORMARS Radio Station, GROTON, CT)
7370.0 kHz
RTTY 10 May/2340Z
PACTOR FEC 11 May/0010Z
AMTOR FEC 11 May/0040Z
14393.0 kHz
RTTY 10 May/2340Z
PACTOR FEC 11 May/0010Z
AMTOR FEC 11 May/0040Z
STATION: NPL (NAVMARCORMARS Radio Station, SAN DIEGO, CA)
7350.0 kHz
RTTY 11 May/0240Z
PACTOR FEC 11 May/0310Z
AMTOR FEC 11 May/0340Z
14465.0 kHz
RTTY 11 May/0410Z
PACTOR FEC 11 May/0440Z
AMTOR FEC 11 May/0510Z
STATION: NUW (NAVMARCORMARS Radio Station, NAS WHIDBEY
ISLAND, WA)
7380.0 kHz
RTTY 11 May/0240Z
PACTOR FEC 11 May/0310Z
AMTOR FEC 11 May/0340Z
13530.0 kHz RTTY 11 May/0410Z
PACTOR FEC 11 May/0440Z
AMTOR FEC 11 May/0510Z
SUBMISSION OF SECRETARY OF DEFENSE TEST MESSAGE ENTRIES.
Transcripts of the RTTY, PACTOR, AMTOR, PSK-31, MFSK and MT63 receiving test should be submitted "as received". No attempt should be made to correct possible transmission errors. Provide time, frequency and call sign of the military station copied, including name, call sign, and address (including ZIP code) of individual submitting the entry. Ensure this information is placed on the paper containing the test message. Each year a large number of acceptable entries are received with insufficient information, or necessary information was not attached to the transcriptions and was separated, thereby precluding issuance of a certificate. Entries must be sent to the appropriate military address as follows:
a. Stations copying Secretary of Defense message transmitted from AAZ send entries to:
Armed Forces Day Celebration
Commander NETCOM/9th ASC
Armed Forces Day Celebration
Attn: NETC-OPE-MA (MARS) (31)
Fort Huachuca, AZ 85613-5000
b. Stations copying Secretary of Defense message transmitted from NAV, NAV-3, NAV-
4, NBL, NPL or NUW send entries to:
Armed Forces Day Celebration
Chief, Navy-Marine Corps MARS
Cheatham Annex Bldg 117
108 Sanda Ave
Williamsburg, VA 23185-5830
c. Stations copying Secretary of Defense message transmitted from AIR-2 send entries
to:
Armed Forces Day Celebration
AFCA / Chief, AF MARS
203W Losey St
Scott AFB, IL 62225
Details of the amateur crossband transmitting test are here.
SECRETARY OF DEFENSE MESSAGE TEST VIA DIGITAL MODES.
The Secretary of Defense message will be transmitted via digital modes including RTTY, PACTOR, AMTOR, PSK-31, MFSK and MT63 from the stations listed below, including frequencies, mode, and date/time in Zulu (UTC). All frequencies are listed for center of intelligence. Offset as appropriate for your TNC. (Note: Not all stations may necessarily operate on all the frequencies listed, depending on propagation and available equipment.)
Army Stations
STATION: AAZ (HQ Army MARS Gateway, Fort Huachuca, Arizona)
6988.0 kHz
RTTY 11 May 0110Z
PACTOR FEC 11 May 0130Z
MT63 11 May 0220Z
PSK-31 11 May 0250Z
14402.0 kHz
RTTY 11 May 0110Z
PACTOR FEC 11 May 0130Z
MT63 11 May 0220Z
PSK-31 11 May 0250Z
STATION: WAR (Pentagon ARC/MARS Station, Arlington, Virginia)
6988.0 kHz
RTTY 10 May 1700Z
RTTY 10 May 2300Z
MT63 10 May 1715Z
MT63 10 May 2315Z
14440.0 kHz
PACTOR FEC 10 May 1730Z
PACTOR FEC 10 May 2330Z
Olivia 10 May 1745Z
Olivia 10 May 2345Z
Stations copying the Secretary of Defense message transmitted from AAZ/WAR should send their entries to Armed Forces Day Celebration, Commander NETCOM/9th ASC, Attn: NETC-OPE-MA (MARS) (31), Fort Huachuca, AZ 85613-5000.
Air Force Stations
STATION: AIR-2 (Scott Air Force Base)
7831.1 kHz
RTTY 10 May/1930Z
PACTOR 10 May/2000Z
MT63 10 May/2030Z
MFSK 10 May/2100Z
14877.1 kHz
RTTY 10 May/2130Z
PACTOR 10 May/2200Z
MT63 10 May/2230Z
MFSK 10 May/2300Z
Navy/Marine Corps Stations
STATION: NAV (HQ NAVMARCORMARS Radio Station, WILLIAMSBURG, VA)
7346.5 kHz
RTTY 75 baud 10 May/2340Z
AMTOR FEC 11 May/0010Z
MT63 11 May/0040Z
14480.0 kHz
RTTY 75 baud 10 May/2340Z
AMTOR FEC 11 May/0010Z
MT63 11 May/0040Z
STATION: NAV3 (NAVMARCORMARS Radio Station, CORPUS CHRISTI, TX)
7393.0 kHz
RTTY 10 May/2340Z
AMTOR FEC 11 May/0010Z
MT63 11 May/0040Z
13975.5 kHz
RTTY 10 May/2340Z
AMTOR FEC 11 May/0010Z
MT63 11 May/0040Z
STATION: NAV4 (NAVMARCORMARS Radio Station, GREAT LAKES, IL)
7375.0 kHz
RTTY 11 May/0240Z
AMTOR FEC 11 May/0310Z
MT63 11 May/0340Z
14468.5 kHz
RTTY 11 May/0240Z
AMTOR FEC 11 May/0310Z
MT63 11 May/0340Z
STATION: NBL (NAVMARCORMARS Radio Station, GROTON, CT)
7370.0 kHz
RTTY 10 May/2340Z
PACTOR FEC 11 May/0010Z
AMTOR FEC 11 May/0040Z
14393.0 kHz
RTTY 10 May/2340Z
PACTOR FEC 11 May/0010Z
AMTOR FEC 11 May/0040Z
STATION: NPL (NAVMARCORMARS Radio Station, SAN DIEGO, CA)
7350.0 kHz
RTTY 11 May/0240Z
PACTOR FEC 11 May/0310Z
AMTOR FEC 11 May/0340Z
14465.0 kHz
RTTY 11 May/0410Z
PACTOR FEC 11 May/0440Z
AMTOR FEC 11 May/0510Z
STATION: NUW (NAVMARCORMARS Radio Station, NAS WHIDBEY
ISLAND, WA)
7380.0 kHz
RTTY 11 May/0240Z
PACTOR FEC 11 May/0310Z
AMTOR FEC 11 May/0340Z
13530.0 kHz RTTY 11 May/0410Z
PACTOR FEC 11 May/0440Z
AMTOR FEC 11 May/0510Z
SUBMISSION OF SECRETARY OF DEFENSE TEST MESSAGE ENTRIES.
Transcripts of the RTTY, PACTOR, AMTOR, PSK-31, MFSK and MT63 receiving test should be submitted "as received". No attempt should be made to correct possible transmission errors. Provide time, frequency and call sign of the military station copied, including name, call sign, and address (including ZIP code) of individual submitting the entry. Ensure this information is placed on the paper containing the test message. Each year a large number of acceptable entries are received with insufficient information, or necessary information was not attached to the transcriptions and was separated, thereby precluding issuance of a certificate. Entries must be sent to the appropriate military address as follows:
a. Stations copying Secretary of Defense message transmitted from AAZ send entries to:
Armed Forces Day Celebration
Commander NETCOM/9th ASC
Armed Forces Day Celebration
Attn: NETC-OPE-MA (MARS) (31)
Fort Huachuca, AZ 85613-5000
b. Stations copying Secretary of Defense message transmitted from NAV, NAV-3, NAV-
4, NBL, NPL or NUW send entries to:
Armed Forces Day Celebration
Chief, Navy-Marine Corps MARS
Cheatham Annex Bldg 117
108 Sanda Ave
Williamsburg, VA 23185-5830
c. Stations copying Secretary of Defense message transmitted from AIR-2 send entries
to:
Armed Forces Day Celebration
AFCA / Chief, AF MARS
203W Losey St
Scott AFB, IL 62225
Details of the amateur crossband transmitting test are here.
US Army Corps of Engineers QSL Opportunity
From Jim Pogue:
[Editor's note: the annual Armed Forces Day crossband tests are done a week before AFD, so as not to conflict with the Dayton Hamvention.]
Once again, station WUG-231 will offer a special QSL card for SWLs only who hear our station during the ANNUAL ARMED FORCES DAY CROSSBAND MILITARY/AMATEUR RADIO COMMUNICATIONS TEST this Saturday, 10/11 MAY 2008.
Any SWL worldwide who hears us is invited to send a reception report and receive our special commemorative QSL card. This will be different than the one amateurs receive for any contacts they make with us.
You may send your report directly to me at the address below. No return postage is necessary. Frequencies are also listed below. Good luck and I hope to hear from you.
STATION: WUG-231 (10 May 1300Z - 11 May 0200Z)
Frequency Emission Amateur Band
4032.9 kHz LSB 80M
7.360.0 kHz LSB 40M
6.826.0 kHz LSB 40M
14486.0 kHz USB 20M
14663.5 kHz USB 20M
20973.5 kHz USB 15M
Location: Memphis, TN
Address:
USACE Memphis District Office
ATTN: Jim Pogue
Public Affairs Office Room B-202
167 N. Main St.
Memphis, TN 38103-1894
POC: Mr. Jim Pogue
Commercial: (901) 544-4109
[Editor's note: the annual Armed Forces Day crossband tests are done a week before AFD, so as not to conflict with the Dayton Hamvention.]
Wednesday, May 07, 2008
Digital Mode of the "Week:" HF Packet
This is early because I'm going on vacation.
---
"Packet Radio" is an amateur mode used to send data between terminals attached to radios. It really took off in the 80s after the authorization of ASCII on amateur bands. It gets its name from "packet switching," a networking protocol in which data is divided into small blocks (packets) with the address and sequence numbers attached. This allows a station to act as a "node," and connect to multiple users on the same frequency. Incidentally, you're using packet-switching and routing right now, since these are also used in the TCP/IP protocol suite which makes the Internet go.
HF packet, which is what we're interested in, is an adaptation of the VHF packet you might be more used to. It transmits at 300 baud, with a 200-Hz shift, using audio frequency-shift keying (AFSK) of standard single-sideband ham transceivers. Various tone centers have been used by different hardware Terminal Node Controllers (TNCs), with the most common being 2210 and 1700.
The AX.25 link-layer protocol used by amateur packet radio uses a special polarity (or lack therof) called NRZI (Non-Return to Zero Inverted). In this, any bit state transition is a one, and no transition is a zero. Since it's the transitions that matter, mark and space are in practice not relevant. This means that packet can be tuned in USB or LSB with no need to change polarity at the receiver. However, as in RTTY, the receiver dial frequencies are usually (though not always) closer to the listed ones in LSB mode.
Today, software TNCs have pretty much replaced hardware ones, but the underlying link-layer scheme is the same. It's just better hidden. AX.25 uses connections, meaning that one station will connect with the other before exchanging information. However an "unproto" mode is provided for CQs, and a "beacon" mode for all-station-this-net broadcasts. There's also a "monitor" mode, which is what we will use, because it decodes all the packets.
Packets are labeled for type of data, which for our purposes means that they are either control packets or data packets. A lot of control packets are sent, giving the mode a rather high overhead.
The receiving connected station will error-check packets and ask for retries of missed ones. Therefore packet radio, like SITOR-A, slows down as channel noise increases. Even at 300 baud, the need for retries can make real information throughput absolutely glacial, and HF packet just isn't used much for long messages. In extensive monitoring, I've seen a few BBS (Bulletin Board System) connections, a few compressed file transfers (which print as gibberish), and a lot of automatic forwarding of packets (aka "digipeating").
Plain text is 7-bit ASCII. TNCs can switch to 8-bit mode for binary transfers or extended characters, but the one at the other end has to do same.
HF packet sounds like a series of short buzzes. These are much shorter and chirpier sounding than other modes used for e-mail and such. Given the greater chance that long packets will be rejected, it's best to keep the bursts very short.
One interesting mode that is run as an application on top of packet is Automatic Position Reporting System (APRS). This automatically sends the GPS position of the station, or even such data as the weather. It allows hams to track vehicles out in the boonies, or participate in weather observing networks. These are then forwarded to multiple stations, and plotted using slick map software. Obviously, HF has considerable potential here due to its coverage of areas where VHF is unheard of.
The best HF frequency for APRS is listed as 10147.6 USB. This is the worldwide APRS gateway. My receiver gives a 1700-Hz tone center when tuned in this mode. I have it on right now, and an HF station just reported a position in California. This is cool stuff.
---
"Packet Radio" is an amateur mode used to send data between terminals attached to radios. It really took off in the 80s after the authorization of ASCII on amateur bands. It gets its name from "packet switching," a networking protocol in which data is divided into small blocks (packets) with the address and sequence numbers attached. This allows a station to act as a "node," and connect to multiple users on the same frequency. Incidentally, you're using packet-switching and routing right now, since these are also used in the TCP/IP protocol suite which makes the Internet go.
HF packet, which is what we're interested in, is an adaptation of the VHF packet you might be more used to. It transmits at 300 baud, with a 200-Hz shift, using audio frequency-shift keying (AFSK) of standard single-sideband ham transceivers. Various tone centers have been used by different hardware Terminal Node Controllers (TNCs), with the most common being 2210 and 1700.
The AX.25 link-layer protocol used by amateur packet radio uses a special polarity (or lack therof) called NRZI (Non-Return to Zero Inverted). In this, any bit state transition is a one, and no transition is a zero. Since it's the transitions that matter, mark and space are in practice not relevant. This means that packet can be tuned in USB or LSB with no need to change polarity at the receiver. However, as in RTTY, the receiver dial frequencies are usually (though not always) closer to the listed ones in LSB mode.
Today, software TNCs have pretty much replaced hardware ones, but the underlying link-layer scheme is the same. It's just better hidden. AX.25 uses connections, meaning that one station will connect with the other before exchanging information. However an "unproto" mode is provided for CQs, and a "beacon" mode for all-station-this-net broadcasts. There's also a "monitor" mode, which is what we will use, because it decodes all the packets.
Packets are labeled for type of data, which for our purposes means that they are either control packets or data packets. A lot of control packets are sent, giving the mode a rather high overhead.
The receiving connected station will error-check packets and ask for retries of missed ones. Therefore packet radio, like SITOR-A, slows down as channel noise increases. Even at 300 baud, the need for retries can make real information throughput absolutely glacial, and HF packet just isn't used much for long messages. In extensive monitoring, I've seen a few BBS (Bulletin Board System) connections, a few compressed file transfers (which print as gibberish), and a lot of automatic forwarding of packets (aka "digipeating").
Plain text is 7-bit ASCII. TNCs can switch to 8-bit mode for binary transfers or extended characters, but the one at the other end has to do same.
HF packet sounds like a series of short buzzes. These are much shorter and chirpier sounding than other modes used for e-mail and such. Given the greater chance that long packets will be rejected, it's best to keep the bursts very short.
One interesting mode that is run as an application on top of packet is Automatic Position Reporting System (APRS). This automatically sends the GPS position of the station, or even such data as the weather. It allows hams to track vehicles out in the boonies, or participate in weather observing networks. These are then forwarded to multiple stations, and plotted using slick map software. Obviously, HF has considerable potential here due to its coverage of areas where VHF is unheard of.
The best HF frequency for APRS is listed as 10147.6 USB. This is the worldwide APRS gateway. My receiver gives a 1700-Hz tone center when tuned in this mode. I have it on right now, and an HF station just reported a position in California. This is cool stuff.
Sunday, May 04, 2008
Digital Mode of the Week: ASCII
ASCII stands for American Standard Code for Information Interchange. It was developed in the United States as a standard means of encoding text readable by people as bits readable by digital computers. It gradually replaced other such American codes as IBM's EBCDIC and Commodore's PETSCII. US ASCII is something of a de facto standard worldwide.
You're using ASCII right now. It's still the basis for most of the text characters used by computers, although as a subset of several much larger character sets that are now used. Plain text files are still usually straight ASCII. It's still fundamental to most of our digital modes.
ASCII was originally developed at Bell Labs for use with wireline TWX machines (an AT&T version of the Teletype). It is essentially an expansion and reordering of ITA2 to make it more useful to computers or "dumb" terminals with modems attached. Today's ASCII is a 7-bit asynchronous code with 128 characters (starting at zero). The first 33 characters (0-32) are non-printing, consisting of null (all zeroes) plus a number of control codes, and the space/blank character (decimal 32).
ASCII can, of course, be sent by frequency-shift keying, and in fact it wasn't long before hams investigated its use as an improvement to radioteletype (RTTY). However, its greater complexity and speed made results on noisy HF circuits disappointing at best when just using straight ASCII. Instead, it's usually sent by packet radio or other error-checking teleprinting schemes.
ASCII characters are sent with "framing" consisting of one start bit and one or two stop bits (remember Baudot's use of a longer stop). Characters usually map to bytes, and since these have 8 bits in modern computers, there's a bit left over. Various things are done with this extra bit.
Many modems have the option to use this 8th bit as a parity bit. This gives a rudimentary error check. If parity is used, the 8th bit will be set or unset so that every character has an even number of ones (even parity) or an odd number (odd parity). If parity is turned off on 7-bit ASCII, the receiver will (hopefully) ignore the 8th bit.
The 8th bit is also used to expand the character set to the full 255. Although SHIFT IN and SHIFT OUT are provided, setting this bit can also send the expanded characters, essentially treating ASCII as an 8-bit code with no parity check.
Unfortunately, there's no international standard for this, and technically it's something of a misnomer to apply the name ASCII to all 8 bits. The high-bit characters are often dependent on application. They can contain accented letters and symbols used in a particular language, or little pieces of lines and corners useful for drawing boxes on old text based terminals.
All of this leads to those infamous ASCII receiver setup parameters that are used in most of our digital modes. These are character length (7 or 8 data bits), stop bits (one or two), and parity (odd, even, or none). While some straight ASCII software can autobaud, it's usually also necessary to set the baud rate by hand. Common HF rates are 100, 110, 300, 600, 1200, 1800, and 2400.
Usually getting all this right in a short wave listening situation is by trial and error. It helps that there are really only two settings in common use. These are 7E1 (7 data bits, even parity, one stop bit), and 8N1 (eight data bits, no parity, one stop bit). It is also possible to emulate the old ITA2 alphabet by simply transmitting the appropriate character set in 5N1 or 5N2 (5 data bits, no parity, one or two stop bits). You see this done by the French Navy when sending data in newer modes such as STANAG 4285.
Here's the 7-bit ASCII in a compact table found on Wikipedia:
An expanded listing of this code is at this column's web site.
You're using ASCII right now. It's still the basis for most of the text characters used by computers, although as a subset of several much larger character sets that are now used. Plain text files are still usually straight ASCII. It's still fundamental to most of our digital modes.
ASCII was originally developed at Bell Labs for use with wireline TWX machines (an AT&T version of the Teletype). It is essentially an expansion and reordering of ITA2 to make it more useful to computers or "dumb" terminals with modems attached. Today's ASCII is a 7-bit asynchronous code with 128 characters (starting at zero). The first 33 characters (0-32) are non-printing, consisting of null (all zeroes) plus a number of control codes, and the space/blank character (decimal 32).
ASCII can, of course, be sent by frequency-shift keying, and in fact it wasn't long before hams investigated its use as an improvement to radioteletype (RTTY). However, its greater complexity and speed made results on noisy HF circuits disappointing at best when just using straight ASCII. Instead, it's usually sent by packet radio or other error-checking teleprinting schemes.
ASCII characters are sent with "framing" consisting of one start bit and one or two stop bits (remember Baudot's use of a longer stop). Characters usually map to bytes, and since these have 8 bits in modern computers, there's a bit left over. Various things are done with this extra bit.
Many modems have the option to use this 8th bit as a parity bit. This gives a rudimentary error check. If parity is used, the 8th bit will be set or unset so that every character has an even number of ones (even parity) or an odd number (odd parity). If parity is turned off on 7-bit ASCII, the receiver will (hopefully) ignore the 8th bit.
The 8th bit is also used to expand the character set to the full 255. Although SHIFT IN and SHIFT OUT are provided, setting this bit can also send the expanded characters, essentially treating ASCII as an 8-bit code with no parity check.
Unfortunately, there's no international standard for this, and technically it's something of a misnomer to apply the name ASCII to all 8 bits. The high-bit characters are often dependent on application. They can contain accented letters and symbols used in a particular language, or little pieces of lines and corners useful for drawing boxes on old text based terminals.
All of this leads to those infamous ASCII receiver setup parameters that are used in most of our digital modes. These are character length (7 or 8 data bits), stop bits (one or two), and parity (odd, even, or none). While some straight ASCII software can autobaud, it's usually also necessary to set the baud rate by hand. Common HF rates are 100, 110, 300, 600, 1200, 1800, and 2400.
Usually getting all this right in a short wave listening situation is by trial and error. It helps that there are really only two settings in common use. These are 7E1 (7 data bits, even parity, one stop bit), and 8N1 (eight data bits, no parity, one stop bit). It is also possible to emulate the old ITA2 alphabet by simply transmitting the appropriate character set in 5N1 or 5N2 (5 data bits, no parity, one or two stop bits). You see this done by the French Navy when sending data in newer modes such as STANAG 4285.
Here's the 7-bit ASCII in a compact table found on Wikipedia:
An expanded listing of this code is at this column's web site.
Friday, May 02, 2008
KSM Encrypted Broadcast WILL Take Place May 3
KSM's intrepid transmitter engineer has recovered sufficiently to come to the station and make the encrypted RTTY and SITOR-B broadcasts using a classic US military crypto machine from World War II. Details are as follows:
Times: Approximately 1900 and 2100 UTC on May 3.
Assigned frequencies: 8433.0 and 12631.0.
Modes: RTTY and FEC. Baudot transmissions are at 170cps shift, 45 baud. FEC transmissions are at 170cps shift, 100 baud (SITOR-B).
Text will start with a plaintext preamble and will include the settings for the M-209 as well as the key. That will be followed by the encrypted text in five letter groups. Since hardly anyone has an M-209, a software emulator is available here. I have been playing with this, and it's a very slick program.
K6KPH will guard its usual CW frequencies of 7050, 14050, 21050 (3550 on request). Since these frequencies are in the scan with the ship calling frequencies the best bet is to use commercial calling procedure: repeat "K6KPH" (within the limits of FCC identification requirements of course) until the K6KPH operator responds with "DE", then send your call and traffic.
QSL, as always, is to Denice Stoops, PO Box 381, Bolinas, California 94926 USA.
Maritime Radio Historical Society web site
Times: Approximately 1900 and 2100 UTC on May 3.
Assigned frequencies: 8433.0 and 12631.0.
Modes: RTTY and FEC. Baudot transmissions are at 170cps shift, 45 baud. FEC transmissions are at 170cps shift, 100 baud (SITOR-B).
Text will start with a plaintext preamble and will include the settings for the M-209 as well as the key. That will be followed by the encrypted text in five letter groups. Since hardly anyone has an M-209, a software emulator is available here. I have been playing with this, and it's a very slick program.
K6KPH will guard its usual CW frequencies of 7050, 14050, 21050 (3550 on request). Since these frequencies are in the scan with the ship calling frequencies the best bet is to use commercial calling procedure: repeat "K6KPH" (within the limits of FCC identification requirements of course) until the K6KPH operator responds with "DE", then send your call and traffic.
QSL, as always, is to Denice Stoops, PO Box 381, Bolinas, California 94926 USA.
Maritime Radio Historical Society web site
IARU Simulated Emergency Test Is May 3
For us, the most interesting feature of this event is the use of Automatic Link Establishment on amateur frequencies. From International Amateur Radio Union:
HFN is the amateur Global High Frequency Network. The network frequencies and pilot stations are:
3596.0
7102.0
10145.5
14109.0
18106.0
21096.0
24926.0
28146.0
ALE Net: HFN
SLOT
1 [ User's callsign ]
2 KM4BA
3 KQ6XA
4 WA3MEZ
5 K7EK
6 VE2FXL
7 NJ7C
8 WD8ARZ
9 KN0CK
10 N0PWZ
Amateurs will attempt to link up with these stations and pass their emergency power capability in an AMD (Automatic Message of the Day).
While it is not clear, presumably May 3 begins at 0000 UTC, which is on the 2nd in the US. In fact, it is about an hour from this posting.
A "qrg" (frequency) file is available at hflink.com. If you join their Yahoo! group, you can also get the latest version of PC-ALE, which will scan (MultiPSK and SkySweeper won't). I've got it going here, and it seems much more sensitive than previous versions. Thanks to the hflink administrators for making it available to me.
It is important NOT to attempt to transmit ALE with amateur equipment unless you know what you are doing. It's not designed to change bands this fast unless you are using a good autotuner and antenna(s) for all bands. In addition, the amateur rules impose certain technical issues. Read the materials out on the Internet before trying this mode!!!!!!
Operators participate in the Global Simulated Emergency Test by sending ALE text messages to the central IARU GlobalSET European headquarters relayed via the network of ALE Global HFN Pilot Stations. Hams activate their ALE stations, start scanning and sounding before the event, and send messages during the day of the event. In addition to the emergency practice, this provides valuable
knowledge of the resources that can be mobilized in the event of a real emergency.
HFN is the amateur Global High Frequency Network. The network frequencies and pilot stations are:
3596.0
7102.0
10145.5
14109.0
18106.0
21096.0
24926.0
28146.0
ALE Net: HFN
SLOT
1 [ User's callsign ]
2 KM4BA
3 KQ6XA
4 WA3MEZ
5 K7EK
6 VE2FXL
7 NJ7C
8 WD8ARZ
9 KN0CK
10 N0PWZ
Amateurs will attempt to link up with these stations and pass their emergency power capability in an AMD (Automatic Message of the Day).
While it is not clear, presumably May 3 begins at 0000 UTC, which is on the 2nd in the US. In fact, it is about an hour from this posting.
A "qrg" (frequency) file is available at hflink.com. If you join their Yahoo! group, you can also get the latest version of PC-ALE, which will scan (MultiPSK and SkySweeper won't). I've got it going here, and it seems much more sensitive than previous versions. Thanks to the hflink administrators for making it available to me.
It is important NOT to attempt to transmit ALE with amateur equipment unless you know what you are doing. It's not designed to change bands this fast unless you are using a good autotuner and antenna(s) for all bands. In addition, the amateur rules impose certain technical issues. Read the materials out on the Internet before trying this mode!!!!!!
US/NATO Joint Exercise On Until May 14
From Combinedendeavor.net
What this means in standard English is that this annual communication/ interoperability exercise always brings out some good (often unencrypted) digital military exercise traffic in Europe.
Welcome to Combined Endeavor 2008!
This annual, United States European Command (USEUCOM)-sponsored exercise is “in the spirit of” the Partnership for Peace (PfP) C4 Integration and Interoperability Exercise. CE enables interoperability between U.S. and NATO / PfP military C4 equipment by documenting and exercising technical and procedural solutions.
What this means in standard English is that this annual communication/ interoperability exercise always brings out some good (often unencrypted) digital military exercise traffic in Europe.
Thursday, May 01, 2008
Charles Brain's Web Site Vanishes
Those looking for Charles Brain's web site with the "official" distributions of PC-ALE and PC-HFDL got a rude surprise today when it vanished. Those taking the link got a blank white page with the cryptic, "I am sorry but my website got deleted."
The last "official" stable release of PC-HFDL, version 2.031, is still available on this column's web site. It was put there originally by request of Charles to help with his bandwidth issues, and it is a copy of the official msi file in a zip folder.
Since the beta 2.04 was never "officially" released, I won't put it up unless asked to, even though I have the distribution zip archive, and the program has always worked just fine here.
The latest stable, non-MARS version of PC-ALE is 1.062G. There's a beta of 1.062H available here. This one is really intended for amateur radio use, though I have gotten it to work for utilities simply by changing the frequencies and group names in the QRG file. There has been some grumbling about this program by those who preferred the old, terse, rather inscrutable user interface. However, it's the one in use here.
While checking all this, I notice that the frequency 14109.0 is now the amateur ALE "pilot channel," though 14109.5 will be scanned until July of 2008.
The last "official" stable release of PC-HFDL, version 2.031, is still available on this column's web site. It was put there originally by request of Charles to help with his bandwidth issues, and it is a copy of the official msi file in a zip folder.
Since the beta 2.04 was never "officially" released, I won't put it up unless asked to, even though I have the distribution zip archive, and the program has always worked just fine here.
The latest stable, non-MARS version of PC-ALE is 1.062G. There's a beta of 1.062H available here. This one is really intended for amateur radio use, though I have gotten it to work for utilities simply by changing the frequencies and group names in the QRG file. There has been some grumbling about this program by those who preferred the old, terse, rather inscrutable user interface. However, it's the one in use here.
While checking all this, I notice that the frequency 14109.0 is now the amateur ALE "pilot channel," though 14109.5 will be scanned until July of 2008.
Wednesday, April 30, 2008
Pacific Air Route Map
This was made by plotting several hundred aircraft position reports with PC-HFDL and Posfix, then layering the resulting maps with Photoshop. The result was a clear indication of the routes taken by airplanes between the US mainland and Hawaii. These were traced over on a new layer. Then the Posfix plots were dropped out, and the original map was combined with the new darkened lines, and saved as a new Posfix map. Subsequent plots have all been right on.
Sunday, April 27, 2008
Digital Mode of the Week: SITOR
SITOR stands for Simplex Telex Over Radio or Simplex Teleprinting Over Radio. It uses the same type of frequency-shift keying (FSK) as RTTY. Mark and space are used. The shift is always 170 Hz, and speed is always 100 baud.
SITOR was developed in the 1960s for use in the radiotelex and maritime narrowband direct printing services, as an improvement on RTTY. It adds error checking, reducing garble over noisy and fading HF circuits. The trade-off is that timing is far more important than in RTTY. Much tighter technical standards are needed for acceptable communication.
SITOR has two modes, A and B. SITOR-A is a fully synchronous two-way mode for traffic handling. Two stations alternate half-second transmit intervals with half-seconds for listening, exchanging short bursts which give the system its distinctive chirp-chirp-chirp sound. You can't mistake this one.
Mode A uses an error checking protocol named ARQ, for Automatic Repeat reQuest. Messages are broken up into 3-character blocks. The station sending these is the Information Sending Station (ISS). The other station is the Information Receiving Station (IRS). The IRS replies with a signal that the received block passed an error check (ACK for acknowledgement), or that it did not (NAK for negative acknowledgement).
Bad blocks are resent as many times as needed, within reason. The effect is that SITOR-A handles degraded circuits not by garbling the message but by slowing down, to a maddening snail's pace if necessary.
To copy SITOR-A, you need to be tuned to the ISS. Its bursts are a little longer than those of the IRS. With some experience, you can tell the difference. It is tricky for the casual listener to properly phase with the ISS. When you do, most decoders will simply print repeated blocks over and over again.
That incredible screech you hear on maritime telex channels is the SITOR-A tuning marker sent by the coast station. It consists of pulses at the baud rate sent in several bursts a couple of seconds long, usually followed by the station callsign in Morse code keyed with the mark tone.
SITOR mode B is a continuous broadcast system using Forward Error Correction (FEC). It sounds like a sped-up, less chattery version of standard RTTY. Being a broadcast, the only station transmitting is the sender. Everyone else listens. Characters are sent in a stream, but with a built-in redundancy in which each character is sent again three characters later. Such combined repetition sequences are called interleave in the jargon.
The concepts of ARQ, FEC, and interleave come up again and again in different digital modes. Many systems use different interleaves. In this one, ABCDE [end of message] would be sent ABCADBEC D E [end of message]. Characters not received twice are dropped, with the idea being that a missing character is better than a wrong one. Therefore, SITOR-B does not slow down on degraded circuits. If everything works right (a big if), it just stops printing.
SITOR-B is easier to receive than A, but it is still necessary to achieve sync for the error check. The special characters ALPHA and BETA are provided for phasing. This is especially evident in the NAVTEX service, which sends these phasing pairs between each of its short messages.
SITOR also uses a different transmission alphabet, called CCIR 476. The scheme is called 4/7. Each character is 7 bits long, but as an additional error check, there are always a total of 4 ones and 3 zeroes in the character. While a larger number of bits would usually mean a larger character set, this requirement means that most bit patterns are in fact error characters, and the character set is actually smaller. Again, there are LTRS and FIGS cases, selected by the appropriate shift characters. Again, optional USOS (UnShift On Space) is usually provided to partially deal with missed shift-outs.
A ham radio version of SITOR is called AMTOR. The differences between the two are slight, and for us, AMTOR can be considered the same thing. The same software usually works for both. ARRL headquarters station W1AW in CT transmits daily bulletins in AMTOR mode B on the same frequencies as RTTY. AMTOR mode A imposes timing and transmit/receive switching demands that amateur gear is rarely designed for, and it is not widely used.
SITOR was developed in the 1960s for use in the radiotelex and maritime narrowband direct printing services, as an improvement on RTTY. It adds error checking, reducing garble over noisy and fading HF circuits. The trade-off is that timing is far more important than in RTTY. Much tighter technical standards are needed for acceptable communication.
SITOR has two modes, A and B. SITOR-A is a fully synchronous two-way mode for traffic handling. Two stations alternate half-second transmit intervals with half-seconds for listening, exchanging short bursts which give the system its distinctive chirp-chirp-chirp sound. You can't mistake this one.
Mode A uses an error checking protocol named ARQ, for Automatic Repeat reQuest. Messages are broken up into 3-character blocks. The station sending these is the Information Sending Station (ISS). The other station is the Information Receiving Station (IRS). The IRS replies with a signal that the received block passed an error check (ACK for acknowledgement), or that it did not (NAK for negative acknowledgement).
Bad blocks are resent as many times as needed, within reason. The effect is that SITOR-A handles degraded circuits not by garbling the message but by slowing down, to a maddening snail's pace if necessary.
To copy SITOR-A, you need to be tuned to the ISS. Its bursts are a little longer than those of the IRS. With some experience, you can tell the difference. It is tricky for the casual listener to properly phase with the ISS. When you do, most decoders will simply print repeated blocks over and over again.
That incredible screech you hear on maritime telex channels is the SITOR-A tuning marker sent by the coast station. It consists of pulses at the baud rate sent in several bursts a couple of seconds long, usually followed by the station callsign in Morse code keyed with the mark tone.
SITOR mode B is a continuous broadcast system using Forward Error Correction (FEC). It sounds like a sped-up, less chattery version of standard RTTY. Being a broadcast, the only station transmitting is the sender. Everyone else listens. Characters are sent in a stream, but with a built-in redundancy in which each character is sent again three characters later. Such combined repetition sequences are called interleave in the jargon.
The concepts of ARQ, FEC, and interleave come up again and again in different digital modes. Many systems use different interleaves. In this one, ABCDE [end of message] would be sent ABCADBEC D E [end of message]. Characters not received twice are dropped, with the idea being that a missing character is better than a wrong one. Therefore, SITOR-B does not slow down on degraded circuits. If everything works right (a big if), it just stops printing.
SITOR-B is easier to receive than A, but it is still necessary to achieve sync for the error check. The special characters ALPHA and BETA are provided for phasing. This is especially evident in the NAVTEX service, which sends these phasing pairs between each of its short messages.
SITOR also uses a different transmission alphabet, called CCIR 476. The scheme is called 4/7. Each character is 7 bits long, but as an additional error check, there are always a total of 4 ones and 3 zeroes in the character. While a larger number of bits would usually mean a larger character set, this requirement means that most bit patterns are in fact error characters, and the character set is actually smaller. Again, there are LTRS and FIGS cases, selected by the appropriate shift characters. Again, optional USOS (UnShift On Space) is usually provided to partially deal with missed shift-outs.
A ham radio version of SITOR is called AMTOR. The differences between the two are slight, and for us, AMTOR can be considered the same thing. The same software usually works for both. ARRL headquarters station W1AW in CT transmits daily bulletins in AMTOR mode B on the same frequencies as RTTY. AMTOR mode A imposes timing and transmit/receive switching demands that amateur gear is rarely designed for, and it is not widely used.
Saturday, April 26, 2008
No KSM RTTY Today
As you might have noticed, there was no RTTY or FEC SITOR from KSM on Point Reyes, CA today. Your radio is fine. They didn't transmit it. This means the encrypted text was not sent, and those of us who were waiting with virtual cipher machines at the ready will just have to wait another week.
The broadcast had to be cancelled due to illness of the engineer who does the RTTY. They will try again next Saturday, May 3. Times and frequencies are still the same as the ones mentioned below.
The broadcast had to be cancelled due to illness of the engineer who does the RTTY. They will try again next Saturday, May 3. Times and frequencies are still the same as the ones mentioned below.
Thursday, April 24, 2008
KSM Encryption/ Decryption Exercise 4/26 and 5/3
KSM, a licensed commercial station using vintage equipment and antennas at historic KPH on Pt. Reyes, CA, will be doing a very interesting broadcast in World War II M-209 encryption. It's at 1900 and 2100 UTC on April 26 (also International Marconi Day) and a week later on May 3. The key will be broadcast, and listeners are invited to attempt decryption of the message with readily available freeware.
M-209, for those of us who weren't born yet, is a US military mechanical code machine slightly resembling a 6-rotor, patch board-less version of the better known German ENIGMA.
Here's the full release from Richard Dillman of MRHS:
M-209, for those of us who weren't born yet, is a US military mechanical code machine slightly resembling a 6-rotor, patch board-less version of the better known German ENIGMA.
Here's the full release from Richard Dillman of MRHS:
KSM will broadcast messages encrypted with the military M-209 crypto machine via RTTY on 26 April and 3 May.
The idea for the broadcast came up in conversations between myself and Dave Ross as a way for the MRHS to support the Military Radio Collectors Group meet taking place in San Luis Obispo, CA on 2-3 May. We thought it would be fun to give the attendees something to copy on their vintage military RTTY gear and then exercise their M-209 skills by decoding the message. But we thought other listeners may enjoy trying their hand at decoding the message as well, thus this announcement (see below for information about a M-209 emulator in case you don't have access to the genuine article).
MRHS transmitter engineer Steve Hawes, who manages our RTTY broadcasts, was keen for the idea and Dave provided the text so all the pieces are in place. Here are the details:
Dates: 26 April and 3 May
Times: Approximately 1200pdt and 1400pdt
Modes: RTTY and FEC. Baudot transmissions are at 170cps shift, 45 baud. FEC transmissions are at 170cps shift, 100 baud
Frequencies: 8433.0kc, 12631.0kc
Text: Dave's text will start with a plaintext preamble and will include the settings for the M-209 as well as the key. That will be followed by the encrypted text in five letter groups.
Additional information:
MRCG - http://syzen.com/milradio/
M-209 emulator for those who wish to participate but don't have a M-209 -
http://users.telenet.be/d.rijmenants/en/m209sim.htm
MRHS - http://www.radiomarine.org
International Marconi Day is April 26
International Marconi Day is a yearly amateur operating event also of some interest to utility listeners. This year, it lasts from 0000 UTC on 26 April 2008 (afternoon of the 25th in the US) to 2359 UTC, 26 April 2008.
It is organized by an amateur radio club near where Marconi transmitted his historic transatlantic signals. The home page is at http://www.gb4imd.org.uk/
.
K6KPH, the amateur radio station of the Maritime Radio Historical Society at the historic KPH "Power House" on Pt. Reyes, CA, will be active starting at noon Pacific time, 1900 UTC, on Saturday, the 26th. Frequencies are 3550, 7050, 14050 and 21050 kHz.
As always, QSL to:
Denice Stoops
PO Box 381
Bolinas, California 94926
USA
It is organized by an amateur radio club near where Marconi transmitted his historic transatlantic signals. The home page is at http://www.gb4imd.org.uk/
.
K6KPH, the amateur radio station of the Maritime Radio Historical Society at the historic KPH "Power House" on Pt. Reyes, CA, will be active starting at noon Pacific time, 1900 UTC, on Saturday, the 26th. Frequencies are 3550, 7050, 14050 and 21050 kHz.
As always, QSL to:
Denice Stoops
PO Box 381
Bolinas, California 94926
USA
Monday, April 21, 2008
Firedrake Jammer Revealed (CD Available)
Every so often, I run across a web page that just makes my jaw drop off. The latest Oh My God is this Satdirectory article on the source of the Firedrake (Firedragon) jamming signal used by China to cover Falun Gong's "Sound of Hope" broadcast from Taiwan.
One can make a case that this item pertains to world broadcasting, not utilities. However, the signal pops up on or near utility frequencies regularly, as it chases SOH around the bands. Lately, it's been heard daily in the fertile ute hunting ground just above 20 meters, on 14410 kHz around 2300 UTC.
It's actually rather good music, when conditions permit clear reception. It has some real nice drumming. It certainly beats all the other noise blasted into the HF bands by governments that can't handle freedom of opinion.
Well, here's what Satdirectory has to say on Firedrake:
Satdirectory has actually made a CD with the full, 60-minute cycle. Since the copyright status is unknown, this one is available for non-commercial use only, from support(at)satdirectory.com. The only costs are to cover shipping and duplicating.
There's also a 4-minute sample of the high-fidelity audio right off the downlink, in Windows .wma format. Yes, there's some of the cool drumming.
Get it right here. But do go to the site and check out the whole story, with technical paramaters for those with a shot at Chinasat 6B, and some hilarious propaganda art.
One can make a case that this item pertains to world broadcasting, not utilities. However, the signal pops up on or near utility frequencies regularly, as it chases SOH around the bands. Lately, it's been heard daily in the fertile ute hunting ground just above 20 meters, on 14410 kHz around 2300 UTC.
It's actually rather good music, when conditions permit clear reception. It has some real nice drumming. It certainly beats all the other noise blasted into the HF bands by governments that can't handle freedom of opinion.
Well, here's what Satdirectory has to say on Firedrake:
Shortwave Radio Enthusiasts and Ham Radio operators have been watching China's Firedrake with interest. They believe that the primary Firedrake transmitter location is on Hainan Island off the coast of Southern China, however it is believed that there may be other transmitter sites also in use. It has also been noted that the Firedrake audio is a one hour loop with no announcements. This got us thinking at Satdirectory; how does the Firedrake programming get to the transmitter site? Is it delivered by a tape or CD on repeat, or is it like most other Chinese radio, delivered by a satellite link to the transmitter?
Well, a search with our 3 meter dish has found Firedrake! The audio is transmitted on Chinasat 6B within the China National Radio (CNR) satellite feed circuits. Many of the China National Radio feeds are in stereo, however one channel that is solely mono is CNR 8 - The Voice of the Minorities broadcast which features programs in the Kazakh, Korean, Mongolian, Tibetan and Uighur languages. The CNR 8 audio feed to the Chinese transmitter sites can be found on the left audio channel of a feed circuit labelled "Lzh8Rdjy". On the right audio channel of this feed is the audio for the Firedrake transmitters.
Following our discovery we tuned up a shortwave receiver to 17780 kHz which at the time also had the jammer running. The audio from the satellite feed and the shortwave radio were synchronised with no delay. This confirmed that the Firedrake shortwave transmitter site was also being fed by the same satellite feed, otherwise we would have expected a delay of a second or so due to the satellite uplink and downlink path delay when compared to the shortwave broadcast.
Satdirectory has actually made a CD with the full, 60-minute cycle. Since the copyright status is unknown, this one is available for non-commercial use only, from support(at)satdirectory.com. The only costs are to cover shipping and duplicating.
There's also a 4-minute sample of the high-fidelity audio right off the downlink, in Windows .wma format. Yes, there's some of the cool drumming.
Get it right here. But do go to the site and check out the whole story, with technical paramaters for those with a shot at Chinasat 6B, and some hilarious propaganda art.
Sunday, April 20, 2008
Digital Mode of the Week: RTTY (Part 2: Teleprinting over radio)
Having discussed the origins of the 5-bit teleprinting ("Baudot") code, now we can talk about one of the oldest digital modes. This is RTTY, for radioteletype. It has undergone several incarnations, from wire teleprinting (like news wires), through various types of hardware-based radio modems, and finally to just another digital option in multimode computer sound card packages.
RTTY is sent over the radio by keying a transmitter between two tone frequencies corresponding to binary states. These are called mark and space. The process is called frequency-shift keying (FSK, F1B emission).
Direct FSK is still used in some dedicated RTTY equipment, but audio frequency-shift keying (AFSK) is far more common today. It is done by generating the proper modulation of an audio tone, which is then sent to the audio input of a standard single-sideband voice radio. (Note that power is lowered due to RTTY having a continuous duty cycle.)
Either method produces the same signal in the receiver. To the ear, RTTY sounds like a continuous warbling tone with rather clicky bit transitions, and often kind of a busy, chattery pulsation to it.
The difference between mark and space frequencies is the shift (in Hz), and the number of bit transitions sent in a second is the speed (in baud). Sometimes you also see speed in words per minute.
Common speeds are 45 (actually 45.45), 50, and 75. Common shifts are 170, 450, and 850. Characters are sent asynchronously, as they are generated. The five data bits are preceded by a single start bit and then followed by 1, 1.5, or two stop bits. (In practice, a long stop bit just sounds like a brief pause on the tone, making RTTY sound even more chattery.)
RTTY's standard tone center (halfway between mark and space) varies a bit. For the most part, it's around 2210 Hz. RTTY used to require careful tuning to center the tones on their respective filters, but today's decoders are more forgiving. Usually, one simply clicks on or between the two peaks on a display, or the software jumps to the loudest signals. The tone center is sometimes relevant for frequency logging, however.
RTTY dial vs listed frequencies can get pretty ambiguous. One can easily be 2 or more kHz off, and not even be sure which way. If you hear nothing on the listed frequency, tune around.
The third important parameter is signal polarity, which can be "normal" or "reverse." This refers to whether mark or space is the lower of the two tones, preferably when tuned in LSB. Unknown signals require some trial and error to find the speed and polarity which print readable text. Shift is usually more evident.
RTTY has no error check, meaning that any problems with the signal will create gibberish, or no print at all. Missed characters on fades are just something we live with.
The good news is that RTTY may be primitive, but it's still heard all over the HF bands. The bad news is that most of this is encrypted, often in a secure military/ government mode called KG-84. There is absolutely no way to get meaningful copy from it. A few navies, particularly the French, still run RTTY test loops and an occasional real message in the clear. Remaining weather stations in Germany and Canada have regular RTTY schedules.
RTTY in the military can also be referred to as RATT.
Old time RTTY stations stored messages on long reels of perforated paper tape, a character at a time. A procedure named "tape relay" existed for the storage and forwarding of traffic. Tapes were punched by perforating devices attached to Teletype machines, for transmission later. Received traffic could be punched directly onto this tape by a reperforator, and relayed by sending the tape to a reader. Much of RTTY's operating nomenclature such as "brag tapes," "test slips," and "loops," is a holdover from this era.
1950s US Navy tape position
The American Radio Relay League (ARRL) headquarters station W1AW sends long RTTY bulletins daily, on time/frequency schedules listed all over the Internet. Shorter transmissions, by hams shooting the breeze or in operating contests, can be heard up or down maybe 10-15 kHz from 14080.
RTTY is sent over the radio by keying a transmitter between two tone frequencies corresponding to binary states. These are called mark and space. The process is called frequency-shift keying (FSK, F1B emission).
Direct FSK is still used in some dedicated RTTY equipment, but audio frequency-shift keying (AFSK) is far more common today. It is done by generating the proper modulation of an audio tone, which is then sent to the audio input of a standard single-sideband voice radio. (Note that power is lowered due to RTTY having a continuous duty cycle.)
Either method produces the same signal in the receiver. To the ear, RTTY sounds like a continuous warbling tone with rather clicky bit transitions, and often kind of a busy, chattery pulsation to it.
The difference between mark and space frequencies is the shift (in Hz), and the number of bit transitions sent in a second is the speed (in baud). Sometimes you also see speed in words per minute.
Common speeds are 45 (actually 45.45), 50, and 75. Common shifts are 170, 450, and 850. Characters are sent asynchronously, as they are generated. The five data bits are preceded by a single start bit and then followed by 1, 1.5, or two stop bits. (In practice, a long stop bit just sounds like a brief pause on the tone, making RTTY sound even more chattery.)
RTTY's standard tone center (halfway between mark and space) varies a bit. For the most part, it's around 2210 Hz. RTTY used to require careful tuning to center the tones on their respective filters, but today's decoders are more forgiving. Usually, one simply clicks on or between the two peaks on a display, or the software jumps to the loudest signals. The tone center is sometimes relevant for frequency logging, however.
RTTY dial vs listed frequencies can get pretty ambiguous. One can easily be 2 or more kHz off, and not even be sure which way. If you hear nothing on the listed frequency, tune around.
The third important parameter is signal polarity, which can be "normal" or "reverse." This refers to whether mark or space is the lower of the two tones, preferably when tuned in LSB. Unknown signals require some trial and error to find the speed and polarity which print readable text. Shift is usually more evident.
RTTY has no error check, meaning that any problems with the signal will create gibberish, or no print at all. Missed characters on fades are just something we live with.
The good news is that RTTY may be primitive, but it's still heard all over the HF bands. The bad news is that most of this is encrypted, often in a secure military/ government mode called KG-84. There is absolutely no way to get meaningful copy from it. A few navies, particularly the French, still run RTTY test loops and an occasional real message in the clear. Remaining weather stations in Germany and Canada have regular RTTY schedules.
RTTY in the military can also be referred to as RATT.
Old time RTTY stations stored messages on long reels of perforated paper tape, a character at a time. A procedure named "tape relay" existed for the storage and forwarding of traffic. Tapes were punched by perforating devices attached to Teletype machines, for transmission later. Received traffic could be punched directly onto this tape by a reperforator, and relayed by sending the tape to a reader. Much of RTTY's operating nomenclature such as "brag tapes," "test slips," and "loops," is a holdover from this era.
1950s US Navy tape position
The American Radio Relay League (ARRL) headquarters station W1AW sends long RTTY bulletins daily, on time/frequency schedules listed all over the Internet. Shorter transmissions, by hams shooting the breeze or in operating contests, can be heard up or down maybe 10-15 kHz from 14080.
Thursday, April 17, 2008
Acarsd Pre-Release 1.7 Now Available for Testing
We finally got to see the new version 1.7 of acarsd, the free ACARS decoding and logging program that also does HFDL via data transfer from PC-HFDL. Beta versions of this new version have been hard to come by, after some users apparently misunderstood the meaning of the term "beta," as in "help us find the bugs."
This download is a "Release Candidate," something more than a beta but still not the official stable release. You can get it here. Right now the newest versions are Public 1.70 Release Candidate 3 30.03.2008 for Windows, and Public 1.70 Release Candidate 2 29.01.2008 for Linux.
I grabbed RC3 and installed it. The "Quick Install," a DOS program, was hard for me to understand, so I did the full install. There is now a setup screen in acarsd that runs the first time, and lets you set a lot of options that used to be deeply buried in the self-documenting acarsd.ini file. The graphic user interface now has its own .ini file, which I haven't looked at yet.
Several nice new features are apparent. The parsing of messages is a little better. What I was really interested in, however, was the expanded use of the ICAO24 airplane address to help identify aircraft making HF position reports. Basically, the idea is that instead of just logging all these planes as .NO-REG, the program uses this hex ID to look up the registration. This is a big improvement for HF users.
Since this is a pre-release, and since the acarsd documentation has never been especially detailed anyway, it took some digging in the .ini file before I found the option that would enable this search. Once I did that, the ICAO lookup worked as advertised.
So far I've had no major problems with version 1.7 RC. In fact, the only issue of substance I can think of is that so far I've been unable to change UP from Bahamasair to United Parcel Service. This issue is caused by the fact that UPS used to use a different IATA prefix.
It took a while to test all this out, since band conditions have been absolutely putrid. When you can't hear San Francisco on 6 or 8 MHz in Los Angeles, you know it's bad.
This download is a "Release Candidate," something more than a beta but still not the official stable release. You can get it here. Right now the newest versions are Public 1.70 Release Candidate 3 30.03.2008 for Windows, and Public 1.70 Release Candidate 2 29.01.2008 for Linux.
I grabbed RC3 and installed it. The "Quick Install," a DOS program, was hard for me to understand, so I did the full install. There is now a setup screen in acarsd that runs the first time, and lets you set a lot of options that used to be deeply buried in the self-documenting acarsd.ini file. The graphic user interface now has its own .ini file, which I haven't looked at yet.
Several nice new features are apparent. The parsing of messages is a little better. What I was really interested in, however, was the expanded use of the ICAO24 airplane address to help identify aircraft making HF position reports. Basically, the idea is that instead of just logging all these planes as .NO-REG, the program uses this hex ID to look up the registration. This is a big improvement for HF users.
Since this is a pre-release, and since the acarsd documentation has never been especially detailed anyway, it took some digging in the .ini file before I found the option that would enable this search. Once I did that, the ICAO lookup worked as advertised.
So far I've had no major problems with version 1.7 RC. In fact, the only issue of substance I can think of is that so far I've been unable to change UP from Bahamasair to United Parcel Service. This issue is caused by the fact that UPS used to use a different IATA prefix.
It took a while to test all this out, since band conditions have been absolutely putrid. When you can't hear San Francisco on 6 or 8 MHz in Los Angeles, you know it's bad.
Sunday, April 13, 2008
Digital Mode of the Week: RTTY (Part 1: ITA2 Telegraphic Alphabet)
We begin a new Utility World series of basic descriptions of digital modes you hear on the air.
First up is one of the oldest modes, but it is still used widely. It's usually called RTTY, for Radioteletype. In the military, you'll also see references to RATT, also Radioteletype.
RTTY's earliest precursor is the Baudot telegraphy code developed in the 1870s by two people working for Jean-Maurice-Émile Baudot, a French engineer. (Yes, that's where we get the transmission speed unit "baud.") This was a 5-bit code, that became known as International Telegraph Alphabet #1 (ITA1, no longer used).
The Baudot code was improved by Donald Murray and others in the early 20th century, leading to an originally Western Union wireline standard called ITA2. This is still the one used for basic English-language Baudot teleprinting. It is still a 5-bit, 32-state, 58-character code, with longer pauses marking start and stop of characters. The name "Baudot" for ITA2 is not technically correct, but in practice the two names are interchangeable. Several ITA alphabets with higher numbers exist for use in other languages, and of course we don't even have time to talk about "third shift" modes for such non-Latin character set languages as Russian.
ITA2 has no lower case. The cases are LTRS (Letters; all upper case) and FIGS (Figures; numbers and punctuation). The case is changed by transmission of control characters corresponding to each. Since the normal mode is letters case, they can also be regarded as shift in (to figures) and shift out. A missed shift character leads to gibberish, and most RTTY systems have the option USOS (Unshift On Space) as a partial (and only partial) solution.
ITA2 bit states are based on timing, and they do not correspond to the base-2 places used in binary numerical notation, which was not used in mechanical teleprinting. Since a bit is technically a "binary digit," we should probably be calling them something else, but we won't. However, note how many of the ITA2 control characters carried over, with bit changes, into later binary computer codes such as American Standard Code for Information Interchange (ASCII).
The 5 bits were typically stored by punching holes in paper tape run through a perforator machine from reels resembling 16-mm movie film. These were read by tape keyers, which controlled a "current loop" connected to a "terminal unit" that interfaced with mechanical teleprinting machines. Many of these were made by the Teletype Corporation, and so "Teletype" is actually an old business trade name, though it has become somewhat generic.
Messages could be relayed by "reperforating" at the receive site. Note that the character pair RY is sent with alternating 01010 and 10101, testing all possible bit states in the code. Even in this electronic age, the test "slip" RYRYRY..., sometimes accompanied by THE QUICK BROWN FOX... is still common.
Here is the ITA2 code (click for bigger image):
First up is one of the oldest modes, but it is still used widely. It's usually called RTTY, for Radioteletype. In the military, you'll also see references to RATT, also Radioteletype.
RTTY's earliest precursor is the Baudot telegraphy code developed in the 1870s by two people working for Jean-Maurice-Émile Baudot, a French engineer. (Yes, that's where we get the transmission speed unit "baud.") This was a 5-bit code, that became known as International Telegraph Alphabet #1 (ITA1, no longer used).
The Baudot code was improved by Donald Murray and others in the early 20th century, leading to an originally Western Union wireline standard called ITA2. This is still the one used for basic English-language Baudot teleprinting. It is still a 5-bit, 32-state, 58-character code, with longer pauses marking start and stop of characters. The name "Baudot" for ITA2 is not technically correct, but in practice the two names are interchangeable. Several ITA alphabets with higher numbers exist for use in other languages, and of course we don't even have time to talk about "third shift" modes for such non-Latin character set languages as Russian.
ITA2 has no lower case. The cases are LTRS (Letters; all upper case) and FIGS (Figures; numbers and punctuation). The case is changed by transmission of control characters corresponding to each. Since the normal mode is letters case, they can also be regarded as shift in (to figures) and shift out. A missed shift character leads to gibberish, and most RTTY systems have the option USOS (Unshift On Space) as a partial (and only partial) solution.
ITA2 bit states are based on timing, and they do not correspond to the base-2 places used in binary numerical notation, which was not used in mechanical teleprinting. Since a bit is technically a "binary digit," we should probably be calling them something else, but we won't. However, note how many of the ITA2 control characters carried over, with bit changes, into later binary computer codes such as American Standard Code for Information Interchange (ASCII).
The 5 bits were typically stored by punching holes in paper tape run through a perforator machine from reels resembling 16-mm movie film. These were read by tape keyers, which controlled a "current loop" connected to a "terminal unit" that interfaced with mechanical teleprinting machines. Many of these were made by the Teletype Corporation, and so "Teletype" is actually an old business trade name, though it has become somewhat generic.
Messages could be relayed by "reperforating" at the receive site. Note that the character pair RY is sent with alternating 01010 and 10101, testing all possible bit states in the code. Even in this electronic age, the test "slip" RYRYRY..., sometimes accompanied by THE QUICK BROWN FOX... is still common.
Here is the ITA2 code (click for bigger image):
Tuesday, April 08, 2008
New Cycle 24 Spot Emerges
After a couple of days with no visible sunspots whatsoever, a tiny Cycle 24 spot has just emerged.
Currently, there is something of a controversy over the precise nature of Cycle 24. While the mainstream prediction is for a fairly energetic cycle, there is an alternate theory. Its proponents argue that the length of Cycle 23 (longest ever recorded) is evidence that Cycle 24 will be late and weak, and in fact will begin a long term decline in solar activity leading to a sort of mini Maunder Minimum (the period in the seventeenth and eighteenth centuries of no sunspots at all, and a mini ice age in Europe). This, of course, would pretty much spell the end of consistent F-region skip propagation above 21 MHz.
Note that recent fading on HF was the result of a coronal hole, not sunspots or solar flares.
We shall see what we shall see.
Currently, there is something of a controversy over the precise nature of Cycle 24. While the mainstream prediction is for a fairly energetic cycle, there is an alternate theory. Its proponents argue that the length of Cycle 23 (longest ever recorded) is evidence that Cycle 24 will be late and weak, and in fact will begin a long term decline in solar activity leading to a sort of mini Maunder Minimum (the period in the seventeenth and eighteenth centuries of no sunspots at all, and a mini ice age in Europe). This, of course, would pretty much spell the end of consistent F-region skip propagation above 21 MHz.
Note that recent fading on HF was the result of a coronal hole, not sunspots or solar flares.
We shall see what we shall see.
Monday, April 07, 2008
HF-GCS Goes Crazy
For two days now, activity on the US Air Force High Frequency Global Communications System has been far busier than normal. Right now (0110 UTC) 11175.0 kHz USB is going crazy.
The activity resembles the Nightwatch net (a TACAMO airborne CP and supporting units), but there are way too many players. Emergency Action Messages (EAMs) are going out far more frequently than usual.
At 0110, "Aircraft 113" is working "Aircraft 115" for a radio check.
At 0122 FOUL LINE is passing multiple EAMs, and at 0124 he is "standing by for traffic."
Most other players are also using joint tactical callwords, though there is also a unit with a CHARLIE WHISKEY prefix (US Navy) simultaneously patching to Duty Office. Yes, I have QRM here, though they all seem able to hear each other where they are.
Highly experienced military monitor Jeff Haverlah heard one of the "for" format EAMs, sent to something like six units at once. According to Jeff, this hasn't happened in years.
Best guess is an exercise, and a big one. Anyone who knows what's up can e-mail this column at the usual drops.
The activity resembles the Nightwatch net (a TACAMO airborne CP and supporting units), but there are way too many players. Emergency Action Messages (EAMs) are going out far more frequently than usual.
At 0110, "Aircraft 113" is working "Aircraft 115" for a radio check.
At 0122 FOUL LINE is passing multiple EAMs, and at 0124 he is "standing by for traffic."
Most other players are also using joint tactical callwords, though there is also a unit with a CHARLIE WHISKEY prefix (US Navy) simultaneously patching to Duty Office. Yes, I have QRM here, though they all seem able to hear each other where they are.
Highly experienced military monitor Jeff Haverlah heard one of the "for" format EAMs, sent to something like six units at once. According to Jeff, this hasn't happened in years.
Best guess is an exercise, and a big one. Anyone who knows what's up can e-mail this column at the usual drops.
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