[aprssig] FW: FM Squelch blocks everything!

Robert Bruninga bruninga at usna.edu
Fri Feb 3 07:58:21 CST 2017


Fired up our next UHF cubesat card for first test and the ground station
got full S9 carrier but signal was full of noise totally masking the data
tones.



Turned off.  Channel was clear. Then opened squelch and there was S9 noise
over 5 Mhz around our UHF downlink.

Went down the  halls with HT and signal tapered slowly down in all
directions.



Came back and with 1” of wire in the HT antenna connector narrowed it down
to a cheap battery charger.



Lesson over and over again, is that a squelch HIDES everything  Even 20+S9
noise sources.  Zero bars while squelched.



Reminded me of when we had local repeater problems.  Turns out it was the
megawatt balloon radar operating in VHF looking over Washington DC.  No one
could hear it with their radio squelched.  But open the squelch and every
channel throughout 2m would show 60+S9 bars on the noisy trash.



It was similarly baffling at the peak of packet in the 90’s when some hams
would complain that their packet system wasn’t working, and yet they never
turned up the volume to listen by ear to the channel to see what was going
on.  I still see that sometimes in our students who think that all you have
to do is hook-up two wireless thingy’s and is should just work… but never
think to listen to a channel or use a spectrum analyzer to see what they
are dealing with.



Turns out, this battery charger (now that I remember) was the SAME one that
got me several years ago.  I was just too old to remember until I had again
done the full DF search through the entire academic building and ended up
right back at the same point.



The older we get the more we have to learn over and over again ;-)

Bob, WB4APR
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