[amsat-bb] Re: Doppler Tuning Convention Question

Mon May 31 15:06:59 PDT 2010


MacDoppler, SATPC32, Ham Radio Deluxe, and other programs all support what
has been called the One True Rule.  The usual name for the implementation is
Full Doppler Tuning.  You are doing it right.  When everyone does this, it
provides a very pleasant opportunity to talk instead of tune.  It also keeps
from drifting all over another QSO, though the transponders are seldom full
these days.

However, that is not to say that people not using this are doing it wrong,
exactly.  There are still many rigs in use which do not have the capability
for computer frequency control.  In the old days, the rule was to tune the
highest frequency, whether uplink or downlink, since this is where the
Doppler shift is greatest.  Take a look at KB5MU's original article and
updates here:


My suggestion is to use full tuning until you find that the other operator
isn't.  Then adapt, usually by turning off the updating for the lower
frequency.  It isn't worth getting doctrinaire about it.  However, by using
the One True Rule as the default, you set a good example and encourage the
movement of other operators in this direction.  As you will find, it is
truly painful to do it the manual way after getting used to automagic
tuning.  As we move above 70 cms, full tuning truly becomes necessary.



-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of John Belstner
Sent: Monday, May 31, 2010 3:36 PM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Doppler Tuning Convention Question

I know there is a lot of discussion on this subject in the AMSAT archives,
but I've recently read a few posts to the BB that have me confused.

Just this weekend I got my Sat station on the air (FT-736R w/MacDoppler) and
I noticed that the MacDoppler program I use adjusts both the TX and RX
frequencies during the satellite pass.  I'm assuming this is to keep my
signal located in the same place in the transponder.  The program seemed to
work quite well.  I was able to copy several QSO's on VO-52 and made a
couple contacts as well.

One thing I noticed is that about half the QSO's I copied did not require
any manual tuning on my part (MacDoppler adjusted the RX correctly) while
the other half did.  According to MacDoppler, those that did require manual
tuning were moving around within the transponder passband.

I've read a few posts (one as recent as today) that suggested the convention
is to keep the RX frequency fixed and manually adjusting the TX frequency
while monitoring the downlink.  Looking through the AMSAT archives this is
the old convention prior to the popularity of tracking software and CAT
control.  So my question is, are there two conventions? or do I not have my
software configured correctly?

Sorry for what might seem like a stupid question, but I'm a newbie to this
facet of Ham Radio.  BTW, I'm having a blast!


John Belstner
w9en at arrl.net

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