[amsat-bb] Re: Doppler Tuning Convention Question

Luc Leblanc lucleblanc6 at videotron.ca
Tue Jun 1 00:32:22 PDT 2010

This thread is cyclic but it is ok to be revisited time to time.

> 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.
> Alan

> Tim,
>      Speak for yourself :-)  In the 20+ years I have been a satellite
> operator, I have never gotten computer doppler control to work right on the
> linear birds.  It works great on FM, but I always wind up fighting it on the
> linear birds.  As soon as I tune the other guy in the computer moves me off
> frequency.  It's so much easier to just listen and adjust on the fly.
> 73,
> Joe kk0sd

> And since we're on the topic ... has anyone else noticed that the latest
> edition of "The ARRL Satellite Handbook" uses VO-52 as the example for
> Doppler tuning - and that it suggests that newcomers who are manually tuning
> for Doppler park their transmit frequency on the UHF uplink and tune the VHF
> downlink (i.e., the exact opposite of the One True Rule)? That is really
> mystifying and disappointing.
> 73 to all,
> Tim - N3TL

The one "true rule" is fine when your "Highest" frequency is your downlink frequency "The frequency you adjust at your transceiver"
and the ARRL satellite handbook is giving the correct way with AO-52 i will try to explain it below for the linear satellite.

Those who are fully auto doppler controlled always correct their uplink and downlink frequency to be at the same spot on the satellite to 
maintain the same audio pitch. Under normal standard work we should all adjust the audio for "normal voice" but some prefer high pitch 
voice and some low pitch voice.  Auto doppler correction can be set to maintain your audio pitch preference but if the other station adjust 
his station for a low pitch it can be annoying for some operator who prefer high pitch voice (Ore vice versa) but it can be corrected just 
in cheating your RX base frequency a bit.

The main issue:

If you enter in a QSO with a fully doppler corrected station and you follow the "One true rule" it is fine but not if this highest 
frequency is your TX frequency. When you adjust your uplink (TX) frequency you will change the normal frequency the receiving station PC 
doppler tracking program is expecting. Those with full auto doppler correction should disable their RX auto correction and they will have 
to manually adjust their downlink frequency when an another station is not auto correcting or manually correcting his uplink frequency.

The biggest impact when you don't adjust or that you manually adjust your uplink frequency is that you can drift over another QSO. The ARRL 
Handbook is correct when they give the VO-52 example but they should give the explanation and this explanation is not easy to understand 
for a new satellite user.

In an ideal satellite world all the users should use auto doppler correction. In a less than ideal satellite world all the user should use 
uplink auto doppler correction and in the actual real time satellitte world be prepared for the worse... and be flexible...

There is also another chapter on the auto doppler correction when you will try to answer a CQ call but depending of your type of 
transceiver and type of doppler correctrion software you will have to experience your own ways just take my station as an example.

My FT-847 in CAT mode does not send any data back to the PC (First version of the FT-847) the transceiver can only received data from the 
PC and if i want to answer a CQ call i have to reenter the new uplink and downlink frequency of the calling station and try to tweaked them 
during the QSO it is a lot of work on a 10 minutes pass...

There is a lot a flavour in the doppler correction world but IMHO the uplink frequency should always be auto corrected and if it is not 
auto corrected the TX frequency should never be adjusted only if you drift on another QSO or if someone else is drifting on you. There no 
perfect solution aside of the full auto doppler correction.

I'm using full auto doppler correction when  transponder activity is low as i always ended up stepping over a lot of station and be stepped 
on when there is a lot of traffic on a transponder. The worse case i saw was on AO-40 one fellow who was in full doppler correction ask the 
other station to move away as he move over the other QSO'S telling he's having priority over the manual corrected stations...

A suggestion is it possible to have a section on a transponder devoted only for those who are using auto tracking in voice mode? lets say 
the upper end section?
There is nothing perfect only imperfect solutions.


Luc Leblanc VE2DWE
Skype VE2DWE


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