[amsat-bb] Old school cool

Lizeth Norman normanlizeth at gmail.com
Mon Aug 25 18:42:03 UTC 2014

Hi all!
Between changing and feeding my two very small children, I'm spending
quality time with my station and Fun Cube Dongle. Listening around, I
find UO-11 still transmitting what appears to be telemetry. My
software modem won't decode it. I suspect that the telemetry frames
are not in compliance with AX.25, therefore ignored. There is a way to
disable the CRC in this particular modem. Haven't tried that yet.

What type of modem is used to receive UO-11? The internet suggests
converting a telephone type unit. I remember turning down a boxful of
1200 baud modems. Ham radio is a pack rat/hoarder's hobby.

Why does the 1200 baud AFSK signal from UO-11 look MUCH different
than, say, the RF envelope developed by the ISS packet transmitter?
Can illustrate this with little trouble.

Trawling the net revealed a piece of software written by Doug, KA2UPW,
a few years ago that (surprisingly!!) runs on Win7. It processes audio
files recorded at 11k sample rate with a word size of 8 (!) bits. It
does say Beta.

Have listened up for ANTELsat. Strong on 437.575 (Not the published
primary freq of 437.28!). Managed to collect a few frames of
telemetry. Supposedly the payload will start xmission of a SSTV
picture in martin1 given the correct (published) 1200 baud AX.25
signal on it's VHF command channel. Google for the engineering
document the team prepared for general users.

Still trying to decode received frames from ANTELsat. They (all four I
got over two days, two kinds say the manual!) break the decoders
available. One particular word gives the status of the SSTV
experiment. Probably should try it by hand.

Norm n3ykf

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