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Re: FT-847 AO-40 and Doppler Uplink Correction?



Here's way I do it since all my satellite operations are still manual.

First your right that 435.630 up gives 2401.360 down without Doppler.  The
other thing to consider is how accurate is your down converter's LO.  In my
case by comparing the predicted Doppler shifted beacon frequency to my
receive I have learned that received signals on my downconverter are
consistently 5 kHz high.  So I would listen on 2401.365 when uplinking
435.630.  My experience is that you can just shift you uplink frequency by
the same amount as the downlink Doppler and be within 5 kHz or less.  So
with -26 kHz of Doppler I'd ul 435.604 and listen around 2401.365 +/- 5.
Also if I give someone a dl spot on IRC I always subtract my known down
converter offset.  Likewise if someone gives me a dl to listen to I tune up
5 kHz.

Lee-KU4OS

----- Original Message -----
From: "hasan schiers" <schiers@netins.net>
To: <amsat-bb@AMSAT.Org>
Sent: Saturday, July 21, 2001 19:54 PM
Subject: [amsat-bb] FT-847 AO-40 and Doppler Uplink Correction?



I'm showing a doppler of about -26.87 Khz at 0300 utc tonight (predicted).
I'm trying to pick a freq pair to put into the 847 that will help me find
myself.

435.630 up corresponds to 2401.360 down....without doppler.

With -27 khz of doppler at 0300, what would be the predicted frequency I
would find myself on actually?

How much of the 27 khz of doppler do I need to make up for on the UPLINK of
435.630, in order for me to actually show up on 2401.360?

(I know this is a dumb question, but bear with me)

Listening for the beacon is easy..just subtract doppler from 2401.332 and
bingo...there it is. My question seems a bit more complicated....what
adjustment do I apply from a non-doppler corrected uplink freq so that I
come out on the "predicted" 2401 downlink freq?

The SUB tune function of the 847 is made for VERY slow freq adjustments...I
don't want to have to crank the knob for five minutes trying to get close. I
want to use the direct keypad entry to get really close, and then use the
SUB tuning for the minor corrections required to carry on a qso.

Tnx any and all. 73

hasan schiers, NØAN
schiers@netins.net


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