Scanning with rtl_fm

Ron Hayes ka2rrz at yahoo.com
Sun Apr 28 19:01:36 UTC 2013


Last year our power company changed the meter so they can read it from there office and it seems to be in the VHF area, I havent pin pointed if its a fact yet But I am now getting a large burst I didnt have before.

 

________________________________
 From: Alan Corey <alancorey at yahoo.com>
To: osmocom-sdr at lists.osmocom.org 
Sent: Sunday, April 28, 2013 10:43 AM
Subject: Scanning with rtl_fm
  
I'm using rtl_fm in a scanning (nbfm) situation, and even with the antenna input disconnected and terminated, I get a burst of noise that sounds like a squelch tail maybe once each scan cycle.  They're a little over 1 second apart.  I've tried setting the squelch up to 10000 where I don't get signals anymore, but I still get the noise.

I discovered that if you scan and have the output be a raw audio file, nothing gets recorded when nothing breaks squelch.  This makes time-lapse recordings where all the pauses are taken out.  Very nice, except for the noise bursts.

I'm using:
#!/bin/sh
rtl_fm -N -S -l 132 -p 102 -f 854040000 -f 854240000 -f 854315000 -f 854415000 -f \
854490000 -f 854540000 -f 855165000 -f 855240000 -f 858790000 -f 867350000 \
-f 867715000 /tmp/`date +"%Y-%m-%d_%H%M.raw"`

and recorded
 overnight, but I mostly got noise bursts.

  Alan
-----
Radio Astronomy - the ultimate DX    
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