We have been using the USRP1 with the WBX card Â on it to communicate
with the AO-51 satellite. We are expecting to hear from the satellite
using an Fm Receiver GRC at 435.300 MHz but don’t receive anything as
yet, we are pretty sure about our antenna setup and the GRC are right.
The problem though is a spurious spike of about 17db which appears at
whatever center frequency we tune to in the spectrum. we think that this
might be the problem as that might be jamming the signal which was
supposed be about the same db level. The point of notice for us is that
this spike is always there even without the antenna connected. the fft
is directly the output of the usrp source in the grc so, we are
presuming that the problem might be in the usrp motherboard .Attached is
the screenshots FM receiver spectrum. Did anyone have this problem? How
can we fix it?.