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Re: FO-20 Tuning question.

actually you are sort of correct. in the absence of computer control for 
correcting both uplink and downlink frequencies at the same time (optimal 
doppler correction). you should always correct the higher of the two 
frequencies. this is the frequency that is affected the most by doppler. if you 
have a 2m and a 70cm frequency and you only adjust the 2m, you will have a 
lot of trouble because doppler is affecting your 70cm frequency way more 
than it does your 2m one. 

simply put....no computer control of both...correct the higher of the two 
frequencies irregardless of uplink or downlink. in mode j, it is the downlink, in 
mode b, it is the uplink. 


Date sent:      	Sat, 02 Sep 2000 23:49:21 -0700
From:           	Jim Walls <k6ccc@earthlink.net>
Send reply to:  	k6ccc@AMSAT.Org
To:             	"amsat-bb@amsat.org" <amsat-bb@AMSAT.Org>
Subject:        	Re: [amsat-bb] 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
> satellite.
> 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 frequencies.
> 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.
> 73
> -----------------------
> Jim Walls - K6CCC
> k6ccc@amsat.org
> http://home.earthlink.net/~k6ccc/
> 626-302-8515    FAX  626-302-9999
> AMSAT member 32537 / WSWSS member 395
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Bruce Paige, KK5DO                      Internet: kk5do@amsat.org
Houston, Texas                                
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