[amsat-bb] Re: Fm satellite Frequencies and Doppler

Zachary Beougher zack.kd8ksn at hotmail.com
Mon May 16 15:51:55 PDT 2011

Actually, I just use the VFO on my D7A as well. ;-)

As far as stepping on someone, it is going to happen on a single channel 
satellite, just make sure it is not deliberate.  Listen, if no one is 
calling or in the middle of a QSO, jump in!  Don't be afraid to throw your 
call out.

Another thing that you should definitely consider - full duplex.  In case 
you don't know what this is, full duplex is simultaneously listening to the 
downlink WHILE transmitting.  This prevents a lot of useless QRM.  When you 
call, you can not only tell if you are stepping on someone, but you can hear 
how good/bad your uplink signal is, and you can be sure that you are getting 
through and not just getting stepped on.  You are even ahead of the game - 
the TH-D72A has this feature!  All you need to do is learn how to use it. 
You may, however, want to try a few more passes before diving into full 
duplex.  Full duplex will not do you any good if you have trouble hearing or 
tracking the birds.



-----Original Message----- 
From: Alexander Sack
Sent: Monday, May 16, 2011 5:45 PM
To: Zachary Beougher
Cc: Clint Bradford ; Clint Bradford ; amsat-bb at amsat.org
Subject: Re: [amsat-bb] Re: Fm satellite Frequencies and Doppler

On Mon, May 16, 2011 at 5:25 PM, Zachary Beougher
<zack.kd8ksn at hotmail.com> wrote:
> Alexandar,
> I am not sure how you have it programmed into the radio so far, but I 
> would
> program 5 memory frequencies into your HT:
> (AO27)
> 436.805 (AOS)
> 436.800
> 436.795 (TCA - Time Of Closest Approach)
> 436.790
> 436.785 (LOS)
> Since AO27 switches off way before LOS, you will probably never need the
> last frequency - 436.785 - but these would be the common frequency steps 
> for
> a typical bird like AO51, SO50, etc.  Don't be afraid to make adjustments
> either.  I find that to hear the 30 sec. of TLM right before AO27 switches
> to VOX I have to be at 436.810.  This is probably more a feature of the
> radio itself.  If you are having trouble hear at AOS or LOS, try adjusting
> your downlink by 5kHz.
> You can also add alpha-numeric tags to your frequencies to keep them in
> order:
> AO27-1
> AO27-2
> AO27-TCA
> AO27-4
> AO27-5
> There are many different variations you can choose from.

Let me tell you what I have been doing:

I have programmed my TH-D72A with the TCA as a base.  I switch to it
then move it to my VFO (F+VFO).  When the bird is going to approach, I
instantly go up 10Khz and work from there.  Its actually ridiculously
easy to just switch down via the tuning knob (so programming above
doesn't really buy you much).  Typically depending on the bird's
doppler, I wound up finding the signal a bit lower than 10khz up (its
not like my AL-800 instantly picks up the signal at 5 degree
elevation) but when it does, I'm good for the remainder of the pass.

The AO-51 FAQ page spells it out very nicely.  Knowing the polar chart
in your head for the pass is very helpful.  It allows you to
gracefully move with the signal as the satellite passes over you.

My biggest issue right now is knowing when to call out.  The flurry of
folks calling CQ on each pass where I live (FN20) makes it very hard
to either a) not step on anyone and b) even find a window to get in.
I will keep trying though (maybe when the weather gets a bit better on
the East Coast).



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