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Diving into PSK31

Last night I heard a CQ at 14,073 using the Olivia 8/250 digital mode. It’s not that common… sort of sounds like a cat doing somersaults on an electric piano. After quite a while the station finally gave up… having made no contacts.

I wanted to make that QSO so badly… just because he was a solid 599, but I didn’t have the transmitter hooked up!

The event motivated me to figure something out. Although not the cleanest connection, I wired the audio output of the computer directly to the HF radio’s patch input. Then, because my computer has no serial port, I used the VOX rather than the PTT input to trigger the transmitter. Of course the audio was a tad hot, but by dropping the mic gain low and adjusting the computer’s audio output level, managed to get a clean signal with no obvious distortion.

At this point, with the CQer long gone, how could I figure out if the rig was getting out? Decided to dive into the pool with PSK31 on 14.070. My first contact was N8MJK, Erik, in Cabrillio, CA. He gave me a good report, as well as quite a few useful hints on how to work PSK31. (He’s also an old Amiga Computer user, so that was cool.) Managed to make a few more contacts, and each presented interesting challenges.

Well… I learned a lot, and I can tell you that PSK31 is a blast. It’s sort of like CW in a way, because you’re juggling copy with trying to figure out the content of your next transmission at the same time… all at about 31 baud.

Anyway, it’s easy to get started. Give it a try. Dive in.

And yes, I’ll wire up a better computer-to-transmitter connection… maybe via a pot or transformer.

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  1. 2010/08/26 at 1:47 PM

    I have use it in the past (Fldigi of course) and had several good contacts. It was alot of fun, watching the waterfall display and picking out the weak signal that I could not hear but could copy on the computer!!! thats amazing to me, a signal I cant hear in the static, but the computer can decode it.

    The interface that worked best is quite simple, I took the transformers off of a couple of old modems I had lying around and wired up some patch cables and a pot across the input of the transformer (5-10k). the 600 ohm transformers give a nice match and eliminate any strange ground loop issues. I used one for input and one for output.

    I also wired up a diode/resistor/2N222 for the PTT and connect it to a serial port, and configured the software to use the DTR line to drive PTT.

    What I found was that for the most part, the VOX worked just as well and I didn’t really need the added circuit. On a older radio with no VOX this would be necessary.

    One of these evenings, we should try some of the other exotic modes and experiment a bit. It can be a lot of fun and a great learning experience.

    – Cody KC6UNN

  2. 2010/08/26 at 8:07 PM

    Ah… a good idea… using the modem transformers for the interface. I’ll do that.

    Probably next Weds I’ll try some of those other modes… let me know if you’ll be around. It is helpful to have someone locally on a QSO to check out signals.

    -Carl KB6ZST

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