[amsat-bb] Solved! Icom 821 and SatPC32 uplink frequency weirdness

Stephan Greene ks1g04 at gmail.com
Wed Jun 6 17:55:05 PDT 2012

...and there was much rejoicing.

Trying to get back on the satellites after many (10 year?) hiatus.
[Yes, I missed AO-51, Arrisat, and a lot of the earlier cubesats.
Sigh.]  Trying to use SatPC32 to control my Icom 821H and I was seeing
weird behavior and having trouble finding and staying tuned on my
downlink.  Manual control worked fine, but I wanted the computer
taking care of some of the work for me.  Finally noticed that the
frequency jumps were EXACTLY the default repeater offsets used when
the rig is in FM/repeater mode.  No idea how the satellite section got
that way (hidden menu triggered? stray bit flip?) but it happened
whenever SatPC32 sent frequency corrections (either automatic Doppler
correction from the software or tuning via keyboard commands) while I
was transmitting.

Solution was a full reset of the radio.  Satellite mode works as it
should, confirmed by some nice, computer-supported voice QSOs on AO-7
and VO-52 this evening.

So, to summarize (and hopefully make it easier for anyone searching
amsat-bb in the future if they run into this):

Problem: Icom 821 in satellite mode. Sub-band transmitter frequency
jumps +600 kHz (2M) or -5 MHz (70cm) while transmitting in CW, SSB,
and FM, as soon as software sends a frequency correction to the radio.
 No jumps or problems when just listening and tuning across
transponder.  Manual satellite mode (software control off) behaves
normally.  Manual does not indicate satellite mode has a repeater
offset feature.

Solution: Full reset of radio, reconfigure radio as needed (interface
baud rate and verify address) for software control.

Thanks to the folks I contacted direct (searches of amsat-bb archives
for SatPC32 and Icom 821 issues) for their suggestions and
encouragement.  Sometimes a problem that appears to be between the
radio & the computer or software is due to the radio, not the

73, hope to work many of you on the birds.
Steve KS1G FM18hx
ks1g at amsat.org

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