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

[Juha Vierinen]

Hi guys,

Thank you for your helpful suggestions. We still haven't managed to pinpoint where the signal is coming from, but we have just dispatched a black SUV with a three letter acronym stencilled on it (our university's initials) to hunt for the signal with a spectrum analyzer and a yagi.

Yesterday the interference was a 440.4 MHz and during the night it went down to 440.0 MHz. Today it has drifted up and down between 440.0 and 440.2 MHz. This is very annoying as our frequency is 440.2 MHz. Based in the wild fluctuation in center frequency (including > 20 kHz jumps), However, the signal at close inspection kind of looks like FSK, so maybe whatever it is, isn't working properly anymore.

I recorded a 10 second snippet of 50 kHz baseband signal in interleaved I and Q with 32-bit floating point format. In python, one would read this with this command:

> import numpy

> z = numpy.fromfile("rfi.bin",dtype=numpy.complex64)

The file can be downloaded here:

http://www.haystack.mit.edu/~j/rfi.bin

You can probably feed this into gnuradio with the filesource and complex data type.

Patrik, you are doing cool stuff with the POES satellite receiving. I wish I had time to try that at some point. 

juha

On Sun, Dec 8, 2013 at 5:38 AM, Patrik Tast <address@hidden> wrote:

Terve Juha,

Some animal neck collar TX:er are very close to that feq (440 MHz).
It could be on a wolf, reindeer or a hunter that use a *home brew*
(illegal) collar on his dog. Building a *home brew* dog collar is
popular today since you can get parts without any questions asked...

I would contact the person who count wolfs near you.

Eagles here (Vaasa, FI) use ARGOS up-link to POES sats 401.65 and
downlink 465.98 MHz (bw 24/80/110 kHz).

Patrik

On Fri, 2013-12-06 at 13:48 -0500, Juha Vierinen wrote:
> Hi,
>
>
> In the last few days a signal has entered in the center of our
> incoherent scatter radar band. It drifts between 440.1 and 440.4 MHz
> very slowly and has approximately a 10 kHz bandwidth. A scope plot of
> the signal shows something that looks a little bit like frequency
> shift keying. While the frequency is stable on short time scales, the
> signal tends to drift a lot on the scale of days, suggesting that
> whatever is causing this signal, it is broken.
>
> I've attached a GRC plot of the signal. In the plot, the jammer is at
> a +166 kHz offset. The scope plot is centered at this frequency and
> has a 40 kHz bandwidth.
>
> Does anyone have any idea what this could be?
>
>
> juha
>

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