[amsat-bb] Re: How you do DOPPLER correction in Linear Transponders?
gouldsmi at bellsouth.net
Thu Jul 2 11:38:11 PDT 2009
Tim, Fabiano and the BB,
This topic has been discussed for many decades.
Many approaches have valid logic, but there needs to be some recognized
standard or multiple approaches will be used.
Even with a standard, there are always new (and old) users that don't know
about it, and thus don't follow it OR do know and choose not to follow it.
AMSAT adopted the 'One True Rule' decades ago and still stands by it.
There is a copy of 'One True Rule' and a description in the AMSAT "Getting
Started Guide", and has been for years.
'One True Rule' needs a more visible link on the AMSAT web site, but that is
So, the official AMSAT line is to follow 'One True Rule' .
AMSAT VP Operations
----- Original Message -----
From: <n3tl at bellsouth.net>
To: "Fabiano Moser" <fabianomoser at gmail.com>; "amsat-bb"
<AMSAT-BB at amsat.org>
Sent: Thursday, July 02, 2009 1:29 PM
Subject: [amsat-bb] Re: How you do DOPPLER correction in Linear
> The latest edition of "The ARRL Satellite Handbook" contradicts earlier
> versions, which suggested the same approach that Drew has here (i.e.,
> always Doppler-tune the higher frequency) in favor of "parking" the uplink
> frequency and Doppler-tuning the downlink (see the section "Finding
> Yourself ... and Others," which begins on page 5-13 of the handbook). It
> occurs to me that, in general, that is the worst approach to take -
> although I admit to only knowing enough about all of this to be more
> dangerous than not.
> Before I added computer-aided Doppler tuning to my station, I took
> Francesco's approach and always tried to stay at the same downlink
> frequency, Doppler-tuning the uplink regardless of whether it was the
> higher frequency. In reality, my approach is only inconsistent with Drew's
> ONLY on FO-29 because, on AO-7 (when in Mode B) and VO-52 (always in Mode
> B), the uplink IS the higher frequency.
> The reason I believe the 2008 edition of "The ARRL Satellite Handbook"
> offers the worst approach has two elements:
> 1 - the "slipping" on the downlink that Francesco alludes to in his post,
> 2 - the use of VO-52 as the "example satellite" for the description of how
> to find one's signal. The exercise directs readers to Doppler-tune the
> lower of the two frequencies to find themselves on the satellite.
> Later today, I will try the "always tune the higher frequency" rule on
> FO-29, which I admittedly have not every tried. I'm looking forward to
> learning how that works for me since the higher frequency on that satelite
> is the downlink.
> 73 to all,
> Tim - N3TL
> -------------- Original message from Fabiano Moser
> <fabianomoser at gmail.com>: --------------
>> Dear friends,
>> We know that some Satellite Operators use diferent system to doppler
>> For Linear Transponder
>> 1) Adjust uplink and downlink automatic by CAT? (Not always woks, some
>> I´m up or down from the computer adjust)
>> 2) Adjust uplink and downlink manual
>> 3) Keep Uplink fixed and adjust only the Downlink frequency.
>> What is the more indicate method to use?
>> FT-847 have knob to adjust Uplink without change downlink VFO, and I´m
>> it to keep my voice in downlink at same downlink much I can.
>> But I know some operators use fixed uplink.
>> How you do?
>> Fabiano Moser CR7/PY5RX
>> ARISS-PORTUGAL (Amateur Radio on the International Space Station)
>> Representative at Teleconference and Portugal Telebridge Coordinator.
>> "There is no great talent without great will. (Honoré de Balzac)"
>> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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