It’s a good Sunday morning to be working 20m digital modes. Show of hands, how many have worked PSK31, RTTY, or some other mode?
If anyone needs example of an interface circuit for their rig, here are a few:
Here’s an example of Olivia, which uses a multi-tone modulation with forward error correction (FEC). Even at -12 dB S/N, much of the text is readable and you can follow the conversation.
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I worked Guademala this evening on 40 meters using JT-65.
I like PSK-31. Living close to other houses, its nice to be able to operate on low power which these modes allow you to do.
It’s weird but there seems to be very little development in the Amateur service of the truly digital modulations like QAM and QPSK that don’t work on traditional AM/FM receivers.
Most of this stuff seems to be based on legacy tone signaling like PSK-31, Olivia, or Bell 200.
PSK-31 is BPSK, QPSK-31 is QPSK, so they are used.
QAM doesn’t work as ionospheric propagation is unkind to amplitude-modulated signals. Multi-path is a killer to a lot modulation methods which want a linear, time-invariant channel. That’s why you’ll find a lot of multi-tone modems which deal with multi-path by using long tones.
Reasonable point, but it just seems like there aught to be something new going on there with all the digital capability we have now… since you can basically synthesize any signal you want at this point within a reasonable precision.
New modes come around rarely, but HAM seems to be particularly dark age-y with most of its operations… just IMHO
I played around with PSK31 a bit, but really enjoyed JT65 for racking up DX log entries. Amazing stuff.
I suspect the reason is wanting to keep the barrier to entry low, so things are developed that can plug into the microphone and headphone jack. You can do quite a bit there, but you can’t phase shift your carrier, and that blocks much of the newer technologies.
I haven’t looked at the SDR transceivers enough to know if they are doing digital synthesis of the output, and might actually be the installed base that allows one of the phase shift technologies to get off the ground.
Otherwise it is going to take enough people deciding a modern digital mode is worth the cost of a purpose built radio.
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Not really, with SDR radios and custom software this is certainly an area that experimentation is around. BUT, most HAMS don’t have any inclination to do anything but buy a commercial radio and gab with other old folks…
Few do any experimentation, so there isn’t a lot of incentive to develop for the HAM market But very little prevents people from experimenting on their own.
Lots of them out there, you just have to type “SDR transceiver” into the googles.
I tend to agree with @wandrson. I once heard it described as “operators” vs. “makers” by Michael Ossmann (Great Scott Gadgets).
If one is inclined to be a maker, you can certainly experiment on your own. There are also a few groups I know of. I personally belong to TAPR, AMSAT, and North Texas Microwave Society. In particular, there is a group of mostly Dallas-based folks (include @zmetzing) working on a software-defined radio for future satellite payloads. I claim we’re working to push the state-of-the-art in both hardware approach and modulation. (Warning: if you subscribe to the amsat-bb mailing list, you may see an average number of flame wars.)
I also hear good things about the Austin QRP club, but haven’t joined their online forums yet.
jb
Yes, building stuff is cool! AMSAT OSCAR satellites provide a wonderful path along which one spends most of one’s time designing and tweaking radios and antennas, which is then followed by furiously trying to make a QSO or two as the satellite races overhead (in the case of LEO) for 20 minutes or so.
Someday, perhaps, the dream of AO-40 (HEO) will come true…