[amsat-bb] FM signal on FO-29?

Zach Leffke zleffke at vt.edu
Sun Nov 8 22:54:28 UTC 2015

well.. when I say students, I meant graduate students at VT that 
happened to be in the lab when I was doing the experiment.  They work 
with me and Bob, so a few crude words here and there aren't uncommon to 

But good point, probably not the best thing for a public demo if your 
audience is a bit younger.

Actually, I've seen so much FM activity (basically every time I've 
monitored FO-29 since we first came online in late september) that I've 
been toying with the idea of trying to locate where the source emitters 
actually are located based on doppler shift data.  We know the doppler 
between the receiving ground station and FO-29, so we can back that 
out.  We know the transponder mapping, so we can work through that to 
determine what the center frequency is as the signal enters the 
transponder uplink receiver.  What we don't know is the uplink doppler, 
because we don't know where the emitter is and we don't know what exact 
center frequency they are on (but I bet you its in 5kHz steps, maybe 
2.5kHz).  So we have two unknowns.  I'm betting there's a way to work 
through it though, and with enough observations and by watching the rate 
of change of the doppler, I bet there's a way to make an educated guess 
on what their center freq and location are.

Or if someone listening knows Spanish and/or Portugese, maybe we could 
get lucky and hear what cross streets the taxi is going to (if it is in 
fact a taxi).

-Zach, KJ4QLP

On 11/08/2015 05:30 PM, Clayton W5PFG wrote:
> I wouldn't recommend playing the FM audio heard via FO-29 to a group 
> of children. Normally it's not English.  It's most likely NOT a 
> religious broadcast based on their choice of crude words.
> 73
> Clayton
> On 11/8/2015 16:13, Zach Leffke wrote:
>> So yes, in the last couple weeks I've seen a LOT of FM activity on
>> FO-29.  And based on my experience with Friday's pass, which was
>> ascending, I'm leading towards the Central/South America QRM theory.
>> Lots of strong FM activity as the pass started and the satellite was
>> over the lower latitudes, but as FO-29 ascended over higher latitudes
>> towards the north pole, the FM activity died down.
>> -Zach, KJ4QLP
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