I keep trying to like Digital Radio Mondiale. A couple of broadcasts are pretty loud into The Land That Shortwave Forgot aka California. They sound really cool. They don't use IBOC, so there's no analog signal at all. It sounds like the old SELSCAN tones they used to use on the COTHEN net, only more so.
Good ute DXers refuse to be told they cannot extract intelligence from every weird noise out there, so of course I went looking to see what I'd need to hear the digital quality audio on my own little short wave radio. I found out that what I'd need is to modify the radio to send a 12 MHz IF directly to the computer. No thanks. I like my NRD-545 the way it is. Thank you.
If it is true that the implementation of DRM that the industry intends to use is completely incompatible, and there will never be a US $29.95 converter board for analog receivers that can be installed with two wires and an AA battery, we have a problem. Every short wave receiver in the world may someday be useless. This bodes ill for the future of the medium, since the installed receiver base in places like Africa is all that keeps it alive. People who use wind-up radios because they cannot afford batteries are not going to afford new radios either. Bye bye shortwave broadcasting.
And then, of course, there is digital SSTV.
I heard someone complaining on the digital SSTV frequency that he can never decode the pictures. No matter how loud the signal is, he misses segments and everything goes blooey. They asked him what program he was using, and laughed when it wasn't EasyPAL Lite, since that's all they ever use.
Since EasyPAL Lite seems to have a new version out every couple of weeks, I downloaded today's beta (literally dated 4/8), and started it up. Crash-o-rama. I guess it's improving, though. It doesn't hang the computer any more. It just tries to write to nonexistent addresses, and goes quietly.
Sometimes, I am told, things improve if you turn off hyperthreading. Unfortunately, I am very much of the old school, and will go to my grave convinced that good programmers do not ask their users to make BIOS changes. I guess that leaves Digtrx and HamDRM as the working programs, and I will have to be content with sending files to myself.
C'est le guerre.
Showing posts with label DRM. Show all posts
Showing posts with label DRM. Show all posts
Sunday, April 08, 2007
Sunday, March 11, 2007
Digital SSTV Saga Ends
After another day of watching the grass grow, I have decided to go back to utility and leave the digital SSTV experimenters to it. I received a couple more nice pictures, with missing segments, from an amateur in Mexico, who was sending dramatic pictures of women in body paint obviously applied as some sort of art show. These were great stuff, and make me want to look around Google Images for more examples of same.
To see real content is, of course, is rather refreshing, considering the one-note samba that is American analog SSTV. You have the guy that wants us to get Jesus, the one who never met an airplane photo he didn't like, and the one with "YL" in his call who sends pictures of, uh, YLs in rather scanty clothing.
Come to think of it, that third guy can keep on with what he's doing. That scanty clothing thing is fine with me.
Must... think... about... radio... .
Digital SSTV, of course, is not a very good name for it. Digital file transfer would be better, since that's what's going on, and the data could really be just about anything. That's the advantage and disadvantage.
The advantage is that, if everything is received, you have the same file that left the transmitting station, not a grungy decode of a scan of its contents. The disadvantage is that Digital Radio Mondiale in its present state is an audio broadcast mode, and better ways exist to transfer files. There is no repeat procedure for missing information transfer units (packets, segments, whatever), because in audio broadcasting there does not need to be. Segments failing the CRC check are simply discarded, and you don't hear that part.
Of course, the receiving station of a file transfer can always ask for, and get, the missed segments. They've sort of automated this process, with bad segments being logged and requested manually by clicking a button for a "BSR" (Bad Segment Resend?) transmission. This is fine, but obviously the retransmission will probably not be the same segments that people listening on-channel missed. For that, you need redundancy, like in FEC mode. In digital SSTV, real redundancy consists of transmitting the whole file more than once, but that means very long transfer times.
There is also the problem that DRM might not be the best mode for amateur equipment, which at least in the US is not allowed to exceed 1500 watts peak envelope output power. DRM's peak to average ratio is awesome, something on the order of 10 dB. In amateur service, this means that your typical 1500 watt PEP linear cranked to the max will be reading about 120-130 average watts at "full legal output."
Somehow I doubt that we will be seeing whole screens of Internet SSTV widgets showing reception worldwide, as we've had in the analog mode for some time now. (A great one is Worldwide SSTV Cams.)
Now, back to utilities...
To see real content is, of course, is rather refreshing, considering the one-note samba that is American analog SSTV. You have the guy that wants us to get Jesus, the one who never met an airplane photo he didn't like, and the one with "YL" in his call who sends pictures of, uh, YLs in rather scanty clothing.
Come to think of it, that third guy can keep on with what he's doing. That scanty clothing thing is fine with me.
Must... think... about... radio... .
Digital SSTV, of course, is not a very good name for it. Digital file transfer would be better, since that's what's going on, and the data could really be just about anything. That's the advantage and disadvantage.
The advantage is that, if everything is received, you have the same file that left the transmitting station, not a grungy decode of a scan of its contents. The disadvantage is that Digital Radio Mondiale in its present state is an audio broadcast mode, and better ways exist to transfer files. There is no repeat procedure for missing information transfer units (packets, segments, whatever), because in audio broadcasting there does not need to be. Segments failing the CRC check are simply discarded, and you don't hear that part.
Of course, the receiving station of a file transfer can always ask for, and get, the missed segments. They've sort of automated this process, with bad segments being logged and requested manually by clicking a button for a "BSR" (Bad Segment Resend?) transmission. This is fine, but obviously the retransmission will probably not be the same segments that people listening on-channel missed. For that, you need redundancy, like in FEC mode. In digital SSTV, real redundancy consists of transmitting the whole file more than once, but that means very long transfer times.
There is also the problem that DRM might not be the best mode for amateur equipment, which at least in the US is not allowed to exceed 1500 watts peak envelope output power. DRM's peak to average ratio is awesome, something on the order of 10 dB. In amateur service, this means that your typical 1500 watt PEP linear cranked to the max will be reading about 120-130 average watts at "full legal output."
Somehow I doubt that we will be seeing whole screens of Internet SSTV widgets showing reception worldwide, as we've had in the analog mode for some time now. (A great one is Worldwide SSTV Cams.)
Now, back to utilities...
Friday, March 09, 2007
MY FIRST PICTURES!!!!!!
Two days of sitting at the receiver have been rewarded. At 2226 UTC today, W9CY sent a file named UP7.jp2. Amazingly, something appeared in my rx window. I darn near spit my coffee all over the keyboard.
Here is NV6H Digital SSTV First Light:
I wonder what it is. Looks a bit like a Chrysler Air Raid Siren. I think there was something on the orderwire about its being in Hawaii. I missed about 20 segments. Obviously the Irfan View partial feature is working. All in all, not much worse than most of the analog SSTV ends up looking in California on the typical wire antennas used for ute DX.
A mere nine minutes later, the miracle repeated itself! Another picture appeared in my rx window! It's called dq2.jp2. I only lost 11 segments this time. Here's the awesome result, as seen on my very own computer:
This time I know what it is. Thanks to W9CY on the orderwire, I know that it is a Dairy Queen in Illinois!
Conditions seem quite good today. There is no telling what further miracles of human communication await.
UPDATE 2313UTC:
OH MY GOD! There is an AMERICAN EAGLE in my WATERFALL!
The possibilities for conceptual art are endless...........
Here is NV6H Digital SSTV First Light:
I wonder what it is. Looks a bit like a Chrysler Air Raid Siren. I think there was something on the orderwire about its being in Hawaii. I missed about 20 segments. Obviously the Irfan View partial feature is working. All in all, not much worse than most of the analog SSTV ends up looking in California on the typical wire antennas used for ute DX.
A mere nine minutes later, the miracle repeated itself! Another picture appeared in my rx window! It's called dq2.jp2. I only lost 11 segments this time. Here's the awesome result, as seen on my very own computer:
This time I know what it is. Thanks to W9CY on the orderwire, I know that it is a Dairy Queen in Illinois!
Conditions seem quite good today. There is no telling what further miracles of human communication await.
UPDATE 2313UTC:
OH MY GOD! There is an AMERICAN EAGLE in my WATERFALL!
The possibilities for conceptual art are endless...........
Digital SSTV Saga Continues
14233 remains active whenever the band is awake to propagate it.
The DRM has drifted slowly back on-channel, last one being measured at 14232.995, accounting for known receiver errors but not unknown computer clock ones.
One file received toward the end of the UTC day, when signal strengths tend to peak on 20, was reported as received perfectly - no bad segments, no CRC errors, full file integrity. It was a picture, according to the voice orderwire. Nothing happened. Irfan View did not start, DIGTRX did not display anything, and no file was saved anywhere. It is presumably in bit heaven.
Wonder what it was.
Seeking verification, I downloaded WinDRM, which worked, but no joy there either. Another try of a newer version of EasyPAL Lite crashed even harder than the last one, not even making it through its first initialization, while giving streams of errors about writing to nonexistent memory addresses before hanging altogether and being killed from Task Manager. Obviously some underlying runtime module is wrong, missing, or corrupt. Probably not EasyPAL Lite's problem, but radio is about communication, not troubleshooting your operating system.
I note from the Yahoo! group that this is not exactly the turnkey program of all time anyway.
While the quest continues, good old grungy Scottie 2 and Scottie DX look better all the time.
UPDATE 2125 UTC:
Discovered the local loop-back test mode. I am now quite good at sending jp2 files to myself. Software appears fine, and the Irfan View preview works.
Still no decodes here. Most stations are in the Midwest. As most people who live here know, short wave listening in California is often like watching grass grow.
The DRM has drifted slowly back on-channel, last one being measured at 14232.995, accounting for known receiver errors but not unknown computer clock ones.
One file received toward the end of the UTC day, when signal strengths tend to peak on 20, was reported as received perfectly - no bad segments, no CRC errors, full file integrity. It was a picture, according to the voice orderwire. Nothing happened. Irfan View did not start, DIGTRX did not display anything, and no file was saved anywhere. It is presumably in bit heaven.
Wonder what it was.
Seeking verification, I downloaded WinDRM, which worked, but no joy there either. Another try of a newer version of EasyPAL Lite crashed even harder than the last one, not even making it through its first initialization, while giving streams of errors about writing to nonexistent memory addresses before hanging altogether and being killed from Task Manager. Obviously some underlying runtime module is wrong, missing, or corrupt. Probably not EasyPAL Lite's problem, but radio is about communication, not troubleshooting your operating system.
I note from the Yahoo! group that this is not exactly the turnkey program of all time anyway.
While the quest continues, good old grungy Scottie 2 and Scottie DX look better all the time.
UPDATE 2125 UTC:
Discovered the local loop-back test mode. I am now quite good at sending jp2 files to myself. Software appears fine, and the Irfan View preview works.
Still no decodes here. Most stations are in the Midwest. As most people who live here know, short wave listening in California is often like watching grass grow.
Thursday, March 08, 2007
20 Meter Digital SSTV Continues
This activity is pretty much continuous during Western Hemisphere daylight hours, up from 14233 kHz, going as high as maybe 14233.35 at times. They continue to transmit the callsigns in the waterfall. Despite a continuous voice chatter (some kind of orderwire, plus a guy talking about his '53 De Soto) no signals have been anywhere near strong enough here for a decode.
UPDATE 1930 UTC: Currently the USB voice orderwire is on 14320.0, but the correct tuning for the digital signal is 14233.24 +/- around 200 Hz. Mention was made (following the '53 De Soto discussion) of another program called EasyPAL. This apparently implements another widely used mode called HamDRM (Presumably Digital Radio Mondiale). Unfortunately, it crashes and burns if you are using hyperthreading on dual-core Wintel machines with XP Service Pack 2. You have to turn this off in the BIOS, and I didn't feel like doing that, since I use the feature a lot with other processor-eating apps to still have a usable computer for things like radio, while they're thinking away.
UPDATE 2036 UTC: Still nothing even close to decodeable signal levels. Apparently the mode needs a good steady S8 or 9 for perfect reception, and not too much lower for any decode at all. Unless someone local transmits, that is not going to happen on 20 meters at this time of day at this point in the cycle. This explains why I seem to be the last hard core radio hacker ever to hear of digital SSTV. Like so much of HF amateur radio, it is just not that rewarding without the use of large rotary antennas on tall towers, of a sort that will get you sued in most decent US neighborhoods.
This is in contrast to analog SSTV, which will decode even when below the noise, though you don't get much. At least you know your software is trying.
So it goes in the exciting world of digital radio. I knew there was something to be said for R-390s and straight CW.
UPDATE 2205 UTC: Downloaded a new DRM DLL for DIGTRX. For some inexplicable reason, the entire folder is set read-only, perhaps because the program is running. Resetting it only causes it to be set back. An effective work-around was to rename the old DLL while out of DRM mode, then copy in the new one. Now DRM mode of DIGTRX does not crash with hyperthreading enabled. (Of course I could always have tried exiting the program...)
DRM has the advantage that you can indeed watch your software try to achieve a decode, complete with a nice phase constellation to show how things are going. At least the listener knows something's happening.
Still no decodes, however. Dial reading when on-channel in this mode is 14232.95.
UPDATE 1930 UTC: Currently the USB voice orderwire is on 14320.0, but the correct tuning for the digital signal is 14233.24 +/- around 200 Hz. Mention was made (following the '53 De Soto discussion) of another program called EasyPAL. This apparently implements another widely used mode called HamDRM (Presumably Digital Radio Mondiale). Unfortunately, it crashes and burns if you are using hyperthreading on dual-core Wintel machines with XP Service Pack 2. You have to turn this off in the BIOS, and I didn't feel like doing that, since I use the feature a lot with other processor-eating apps to still have a usable computer for things like radio, while they're thinking away.
UPDATE 2036 UTC: Still nothing even close to decodeable signal levels. Apparently the mode needs a good steady S8 or 9 for perfect reception, and not too much lower for any decode at all. Unless someone local transmits, that is not going to happen on 20 meters at this time of day at this point in the cycle. This explains why I seem to be the last hard core radio hacker ever to hear of digital SSTV. Like so much of HF amateur radio, it is just not that rewarding without the use of large rotary antennas on tall towers, of a sort that will get you sued in most decent US neighborhoods.
This is in contrast to analog SSTV, which will decode even when below the noise, though you don't get much. At least you know your software is trying.
So it goes in the exciting world of digital radio. I knew there was something to be said for R-390s and straight CW.
UPDATE 2205 UTC: Downloaded a new DRM DLL for DIGTRX. For some inexplicable reason, the entire folder is set read-only, perhaps because the program is running. Resetting it only causes it to be set back. An effective work-around was to rename the old DLL while out of DRM mode, then copy in the new one. Now DRM mode of DIGTRX does not crash with hyperthreading enabled. (Of course I could always have tried exiting the program...)
DRM has the advantage that you can indeed watch your software try to achieve a decode, complete with a nice phase constellation to show how things are going. At least the listener knows something's happening.
Still no decodes, however. Dial reading when on-channel in this mode is 14232.95.
Wednesday, March 07, 2007
More Ham Funny Noises (This time 20M and legal)
I was trying to track down this weird noise on 20 meters. It sounded a bit like STANAG 4285, a bit like MT63, and at times a whole lot like the backscatter radar. It seemed to be centered around 14233.3 kHz. SkySweeper wouldn't do anything with it, and MultiPSK wouldn't do anything with it.
So I'm watching it on the waterfall, trying to figure out the mode - pilot tones followed by multitone 8PSK - and just then a stronger transmission started up. Here's what appeared on the waterfall:
That's right. There was writing in the waterfall, transmitted by just the right modulation of the signal. (This, in fact, is what sounds like the backscatter radar.)
See something new every day.
Other bursts had different amateur callsigns, signal reports, roger/no copy messages, and finally a smeary little identifier of a program named DIGTRX 3.11.
Google is a wonderful thing. I grabbed DIGTRX and ran it, and found out it's a digital file transfer mode popular with amateurs in South America to send SSTV pictures without the analog noise and grunge. That certainly explains why they were on 14233. The letters are called a "waterfall message," and there are also "waterfall pictures." Yes, real monochrome photos, in the waterfall. Little faxes, sort of. This is all just too cool.
Can't wait to get some amateur signals loud enough to decode the content. Terrestrial radio survives because people keep re-inventing it.
So I'm watching it on the waterfall, trying to figure out the mode - pilot tones followed by multitone 8PSK - and just then a stronger transmission started up. Here's what appeared on the waterfall:
That's right. There was writing in the waterfall, transmitted by just the right modulation of the signal. (This, in fact, is what sounds like the backscatter radar.)
See something new every day.
Other bursts had different amateur callsigns, signal reports, roger/no copy messages, and finally a smeary little identifier of a program named DIGTRX 3.11.
Google is a wonderful thing. I grabbed DIGTRX and ran it, and found out it's a digital file transfer mode popular with amateurs in South America to send SSTV pictures without the analog noise and grunge. That certainly explains why they were on 14233. The letters are called a "waterfall message," and there are also "waterfall pictures." Yes, real monochrome photos, in the waterfall. Little faxes, sort of. This is all just too cool.
Can't wait to get some amateur signals loud enough to decode the content. Terrestrial radio survives because people keep re-inventing it.
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