[amsat-bb] Re: VO52

John P. Toscano tosca005 at tc.umn.edu
Tue Jun 12 04:03:31 PDT 2007

kc6uqh wrote:
> O.K. I have a Icom 820 and for field day I intend to try VO-52 with out computer controlled anything. I have Dos 6.22 , IT and a 386 notebook. Yagis for 2M and 70cm. 
> Question should I adjust the transmit (70cm) or the receive  (2 M ) for Doppler? I relize that either will work but this is a protocall question covering only the FD operation in June.
> Looking for some sound advise not lectures.
> Thanks,
> Art, 

Without computer control, the conventional wisdom is leave the lower 
frequency (2 meters) alone, and tune the higher frequency (70 cm).  This 
should apply on Field Day (lots of rookies) just as well as under normal 

There may also be a preference depending on your specific radio.  With 
the Yaesu FT-847 satellite transceiver, the design of the radio is such 
that in satellite mode with tracking turned on, the main dial controls 
both uplink and downlink (that's what is "tracking"), and the sub dial 
controls the uplink only, so you can correct for Doppler.  In the case 
of VO-52, the uplink is 70 cm so there is no conflict. But with Mode J 
satellites (FO-20, R.I.P., and FO-29, hoping for resurrection) the 
uplink is the lower frequency and so the design of the radio is contrary 
to the "tune for Doppler with the high frequency".  As it turns out, I 
find the sub-tune knob on the FT-847 a real pain in the @$$ to use for 
tuning Doppler, and impossible unless I put the radio into "Fast Tune" 
mode.  So I cheat.  I turn on tracking, find a station by tuning the 
main dial, TEMPORARILY disable VFO tracking, adjust the main dial until 
I hear my downlink, then re-enable VFO tracking. At that point, I can 
tune up and down the passband and the uplink/downlink frequencies stay 
in sync for a short time. Obviously, as the pass progresses, the Doppler 
shift changes, and about 3x as fast on the 70 cm band, so you need to 
continue adjusting, but once you have your downlink and uplink 
synchronized, if you REMEMBER to RE-ENABLE TRACKING, you can quickly 
tune up or down the passband to another station and be at least close to 
being tuned in on both.

YMMV with the Icom 820.  It's been many years since I've seen or touched 
one of them, although the first satellite contact I ever heard was made 
on one during Field Day by an experienced satellite operator (N0BEL).

Good luck!
Field Day 2007 VHF/Satellite Station Manager, Twin Cities Repeater Club, 
operating as W0BU from Minnesota.  (We have been a 3A station as long as 
I've been around, but this year may be a 2A station.)

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