Re: [Discuss-gnuradio] Need help identifying jammer signal

[Ralph A. Schmid, dk5ras]

Thanks for the follow-up, this is similar to a 1 second noise burst every 60 seconds or so we had on our ham repeater. The reason could be identified after months of search by coincidence. The repeater sysop visited his fathers office, monitored the input frequency of the repeater like he had done routinely for months to hear exactly nothing – but there it was, some wideband noise pulse! 100 m from this office a paging system for a facility management team was sitting on a tower, not actively used for years, still transmitting its beacon every minute, and with age the TX started emitting noise along with its POCSAG signal. Gnuradio also would have been useful in our case, but it was way before we knew of this exciting stuff :)

Ralph.

 

 

From: address@hidden [mailto:address@hidden On Behalf Of Juha Vierinen
Sent: Tuesday, December 17, 2013 11:41 PM
Cc: gnuradio mailing list
Subject: Re: [Discuss-gnuradio] Need help identifying jammer signal

 

Last Friday we managed to finally track this thing down. It was a broken FSK telemetry system on an FM radio tower. It was about 30 km Southwest of our radar.

 

I did a small write up about this:

http://kaira.sgo.fi/2013/12/perfect-incoherent-scatter-radar-jammer.html

 

Thanks for all the help. 

 

juha

 

On Wed, Dec 11, 2013 at 4:34 PM, Johnathan Corgan <address@hidden> wrote:

On 12/10/2013 02:00 PM, Miki Lustig - KK6GEO wrote:

> These look like 2pi jumps -- which is the an artifact if the
> unwrapping is not working well.

Sure, I see what you mean.

Backing up and just plotting the unwrapped phase, you can see in the
first image that overall it is increasing at one rate, then shifts to a
lower rate about 1.5 seconds into the file.

The finer structure is much more interesting.  The second image shows
the phase making fast jumps every 500 samples (10 ms), with periods of
oscillation in between.  The detail on this is in image 3.

I still have no idea what this is, but it sort of looks like an
oscillator that is disciplined at 100 Hz.

--
Johnathan Corgan, Corgan Labs
SDR Training and Development Services
http://corganlabs.com