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Re: FO-20 Tuning question.

"David M. Tipton, PhD" wrote:

> I'm aware that Doppler affects downlink on FO-20, but do I need to
> compensate on the uplink as well?  May sound strange, but I'm not really
> sure here....  I've made a handful of contacts on the bird know, and it's
> getting easier, but I'd really like to stay in one place and "ragchew" for
> a few minutes..
> Dave, N8KXA

Basically there are three ways to do the dopler compensation:
Leave the uplink alone and adjust the downlink,
Leave the downlink alone and adjust the uplink,
Adjust both uplink and downlink to maintain the same frequency at the

The third one is the "ideal" way to do it, but it's seldom done.  It requires
that all stations in the conversation be under computer control of
In reality, on the mode J birds, most of the time the uplink is left alone and
people adjust the downlink.  However it will still sometimes be necessary to
adjust the uplink a little as well.  What is commonly done is to just adjust
the downlink, but if you find yourself way off in frequency when the
conversation comes back to you, you can move your uplink to "get on the other
guy's frequency".  Then leave it there unless you need to do that later on.
On AO-10 (in mode B), the proper way is to adjust the uplink as that has more
error, but often it's done the same as the mode J birds.
After you have done it for a while longer it will become second nature and
you'll hardly even think about it.

Hope that helps.

Jim Walls - K6CCC
626-302-8515    FAX  626-302-9999
AMSAT member 32537 / WSWSS member 395

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