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

Alexander Sack pisymbol at gmail.com
Mon May 16 14:45:23 PDT 2011

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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