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)
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