Adventures in Satellite SDR

By JonathanGuthrie, 22 May, 2014

While I'm waiting for new boards to come in for the Arduino-based memory keyer and while I'm waiting for NC4L to get my money order so he can ship my FT-102 back, I'm working on getting back on the satellites. I've decided to try my hand at the linear-transponder satellites. I've watched guys like Andy (W5ACM) operate linear satellites with nothing more than an FT-847 and some well-practiced skills, but I don't have any FT-847 equivalent, and the all-mode radio that I do have is computer-controllable so I can run computer-controlled.

The one small fly in that ointment is that I only have one radio for SSB or CW on VHF or UHF, and that's my IC-706MkIIG. I used it as the receiver when I used the FM satellites those years ago, and used a 300mW handy-talkie as my transmitter. Since none of my HT's will transmit (or receive, for that matter,) CW or SSB, I'm kind of stuck. Or, well, I was kind of stuck. You see, about a year and a half ago, I bought these TV receiver dongles that could be used for some SDR on the very cheap. I never actually did anything with them, but they were there, and I figured if I could create a software receiver to demodulate SSB and CW, then I could use them as my receiver. I don't have a knob to twirl, so I was thinking of putting the receiver under computer control as well.

Thanks to KT5TK, I have an SMA to PAL antenna adapter, and I had a SMA to PL-259 adapter, and an SMA gender-changer already. I was able to hook up the 2m quadrafilar helix to the dongle and this evening, just a few minutes ago, in fact, I was able to receive CW signals from VO-52. I not only heard the Dutch beacon,. but portions of an actual CW QSO.

Actually, my current receiver leaves a lot to be desired. For example, it doesn't (yet!) have computer control. It also centers the receiver passband around the carrier frequency rather than putting it off to one side like a civilized receiver. I think I know how to handle both of those issues, so we'll see.

I also think that my inside antenna is the cause of both some signal attenuation and puts it close the major sources of noise in my house. That's harder to solve because it means I have to get up on my roof and mess around up there and run wires through my attic and stuff like that. It also means I have to spend money on better feedlines and probably a tripod to put the antennas on and I'm thinking an antenna switch so I can connect either the transmitter or receiver to either the VHF or UHF antenna and automatically connect the other to the other.

Anyway, that's what I'm working on while I'm not goofing off.