[amsat-bb] Re: SatPC32 - New Program Feature - Doppler

Fri Mar 23 07:17:51 PDT 2012


Thanks for mentioning this.  I had missed his update.  This makes SATPC32
unique in providing this support. 

There is an article in the July/August 2010 issue of the AMSAT Journal
called "Bringing the One True Rule of Doppler Tuning into the 21st Century."
It explains in some detail the rational for doing this.  If someone wishes a
copy, please contact me OFF LIST and I will send you a PDF.



-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of John Papay
Sent: Thursday, March 22, 2012 7:21 PM
To: amsat-bb at amsat.org
Subject: [amsat-bb] SatPC32 - New Program Feature - Doppler

Erich DK1TB has again implemented another great feature
into SatPC32 V12.8b by means of a "patch" file. You can
find it in the "downloads" link on his website, www.dk1tb.de
Scroll down to Section 7, Patches.

I often hear others talk about meeting someone, usually a
long distance new grid square, on a certain frequency.  Since
doppler is always in play, telling someone you will be on
435.845 is meaningless unless you are both in the approximate
same location.  If the other station is at LOS and you are at
AOS, your dial readings could be 15Khz apart.  It's a great
way to miss a 60 second window.

The trick here is to use the same point of reference.  That reference
would be the frequency you are on at the satellite receiver.  The whole
idea of doppler correction is to be at a constant frequency within the
satellite receiver passband.  To do that you have to adjust your uplink
frequency constantly.  And you have to adjust your downlink frequency to
continue to hear yourself or someone else using full doppler correction.

Erich has now added the option of seeing the frequency you are on at
the satellite receiver.  This is a common frame of reference so if you
tell someone you'll be on 435.845 at the satellite, they can be on that
same frequency even though your terrestrial dial frequencies will be much
different.  Just adjust your receiver or use the up/down buttons in SatPC32
to set your frequency shown in the "Sat" window.  That frequency will remain
constant as your uplink and downlink are controlled by SatPC32.

If you haven't managed to interface your radio with SatPC32, this is just
another reason to do so. Staying at a constant frequency at the satellite
allows many stations to share the bird without drifting into each other.
And being able to know exactly where you are in the passband without doing
the calculation in your head gives you more time to concentrate on making
a successful QSO!  Rumor has it that even a certain Maritime Mobile 
will soon be
controlling his radio with SatPC32.

John K8YSE

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