Digital. It's what's for breakfast.
Feb. 28th, 2012 09:43 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
banjoplayinnerdHam radio isn't all beeps and boops or guys talking like the pilots in the final battle of "Star Wars IV: A New Hope." (Seriously, the first time I saw that movie I was going, "That sounds an awful lot like SSB" - single sideband, a very common ham radio mode.) Hams have always been experimenters, and one of the things they're experimenting with now is the marriage of computers and radios.
I just got a cable yesterday that is supposed to hook my computer's sound card up to my new radio so I can try using some of the new "digital modes". Ever since I first heard about them I've wanted to try them. Hams have been doing two digital modes for decades. The first, Morse code, qualifies as digital because you're just turning your signal on and off. The second, radioteletype (RTTY) got its start several decades ago when surplus teletype machines began to appear on the market. Hams built modems to hook them up to their transmitters and receivers and started making contacts.
The computer has opened up a number of new possibilities. There are now digital modes for specialized uses like bouncing signals off the ion trail a meteor leaves behind as it enters the atmosphere, or off the moon. (My station doesn't have the oomph for moonbounce. It takes quite a bit of skill and a good initial signal to make a contact over a path of almost half a million miles. Maybe someday.) The mode I'm most interested in at the moment is called PSK31.
PSK31 is in some ways similar to Morse code, except instead of turning your signal on and off, you shift the frequency of the signal. RTTY works in a similar way. To give you an idea of why this is so cool (other than the obvious cool factor of having a keyboard-to-keyboard conversation over the air): A single sideband signal might have a bandwidth of 2500 Hz or so. A Morse code signal might have a bandwidth of 300 Hz. A PSK31 signal has a bandwidth of 31 Hz. That means in theory you can fit about 80 PSK31 conversations into the same amount of spectrum space one SSB signal uses. That's pretty cool. There are other advantages to these new digital modes. One is that signals are often detectable at levels far below the weakest legible SSB or Morse signal. Another is, by using TouchTone-style encoding information can often be transmitted faster and more accurately than via traditional modes.
Last night I wasn't able to hear any PSK31 activity on 2 meters, which isn't too surprising because I'm set up primarily for FM voice work. I might be able to hear a bit more when I get the quad up. In the meantime, tonight I might just hook up the 2 meter antenna to the HF side of my radio, because there's a lot more PSK31 activity on the HF bands than there is on 2 meters. Transmitting with such an option would be a very bad idea, but hopefully I can hear something and prove my setup works (or at least that much of it).
I just got a cable yesterday that is supposed to hook my computer's sound card up to my new radio so I can try using some of the new "digital modes". Ever since I first heard about them I've wanted to try them. Hams have been doing two digital modes for decades. The first, Morse code, qualifies as digital because you're just turning your signal on and off. The second, radioteletype (RTTY) got its start several decades ago when surplus teletype machines began to appear on the market. Hams built modems to hook them up to their transmitters and receivers and started making contacts.
The computer has opened up a number of new possibilities. There are now digital modes for specialized uses like bouncing signals off the ion trail a meteor leaves behind as it enters the atmosphere, or off the moon. (My station doesn't have the oomph for moonbounce. It takes quite a bit of skill and a good initial signal to make a contact over a path of almost half a million miles. Maybe someday.) The mode I'm most interested in at the moment is called PSK31.
PSK31 is in some ways similar to Morse code, except instead of turning your signal on and off, you shift the frequency of the signal. RTTY works in a similar way. To give you an idea of why this is so cool (other than the obvious cool factor of having a keyboard-to-keyboard conversation over the air): A single sideband signal might have a bandwidth of 2500 Hz or so. A Morse code signal might have a bandwidth of 300 Hz. A PSK31 signal has a bandwidth of 31 Hz. That means in theory you can fit about 80 PSK31 conversations into the same amount of spectrum space one SSB signal uses. That's pretty cool. There are other advantages to these new digital modes. One is that signals are often detectable at levels far below the weakest legible SSB or Morse signal. Another is, by using TouchTone-style encoding information can often be transmitted faster and more accurately than via traditional modes.
Last night I wasn't able to hear any PSK31 activity on 2 meters, which isn't too surprising because I'm set up primarily for FM voice work. I might be able to hear a bit more when I get the quad up. In the meantime, tonight I might just hook up the 2 meter antenna to the HF side of my radio, because there's a lot more PSK31 activity on the HF bands than there is on 2 meters. Transmitting with such an option would be a very bad idea, but hopefully I can hear something and prove my setup works (or at least that much of it).
