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Full Doppler Controll



Hi all,
Full Doppler Tracking has been discussed on the amsat-bb from time to time
for
many years.
Since I have just implemented it here, I thought that I would try to tell,
what my
experience over the last couple of weeks, have been.

First of all Full Doppler Tracking means to keep your frequency at the
satellite
constant. With two amateurs in different places the satellite is the only
point, that is a common reference.
That is both for the uplink and the downlink frequency.

There is a very good article about this on amsat.org.

http://www.amsat.org/amsat/features/one_true_rule.html

by KB5MU

It is a little bit outdated. Now we have PC programs and transceivers that
allow us to use the knob on the transceiver like we normally do - and the PC
takes care of the doppler correction.

To start with I got SatPC32 up and running. Connected the homemade ICOM
interface
to the IC-910 - and made a lot of setting up of the program.

You have to make adjustments to the "doppler file" to make it work with your
own
transceiver, but that is not too difficult.

Once everything is set-up correctly I were ready to test it in real life.
That was great - especially with another radio amateur with the same set-up
in
the other end.
Even if the amateur in the other end does not use full doppler tracking it
works very well.
All you have to do is to follow her downlink frequency.

Almost hands off - just talk on the SSB satellites FO-29 and VO-52 (HAMSAT).
No - not always that easy - FO-29 and VO-52 are not completely stable in
frequency
according to my findings. I think it has to do with the temperature in the
satellites.
Therefor you sometimes have to make fine adjustments to your uplink
frequency.
That can be done by the + and - keys if you use SatPC32.
On the FM satellites it is no problem once you have adjusted the doppler
file to
your own transceiver.

I feel like a very well known radio amateur who demonstrated Forward Error
Correction on AO-40 at the AMSAT-UK Colloquium - his comment was:
"Why did we not do this several years ago"

SatPC32 is made by DK1TB, Erich, and all the monies for registration goes to
AMSAT.

Lots of other programs can do the same. InstantTrak, Hallosat are just two
examples.

A friend, OZ9VQ, made the interface with a MAX232. Low cost compared to
ICOMs
solution.

Happy New Year from Copenhagen.

73 OZ1MY
Ib
----
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