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.

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.

US Army Corps of Engineers QSL Opportunity

From Jim Pogue:

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.]

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.

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.

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

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:

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

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.

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.

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.

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.

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.

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:

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

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:

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.

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.

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.

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):

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.

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.