[Discuss-gnuradio] USRP with Basic_RX

I'm trying to "carve off" about 250Khz of bandwidth around 38.5MHz,
(actually any frequency
between about 25MHz and 40MHz) using a Basic_RX and a USRP2.

In GRC, I created a simple flow-graph with a USRP2 source, and an FFT sink.

I set the tuning parameter of the source to 38.5MHz, and what I get on
the FFT is a flat-line at
-410dB! Now, granted, I don't have the inputs connected to anything
yet, but I would expect there
to be *some* noise, and -410dB seems, well, like bad physics :-)

Cribbing from hfx2.py in gnuradio/*examples*/python/apps it seems that
this should "just work".

Am I missing something? I thought that the FPGA would "do the right
thing" in the case of the Basic_RX,
and use the DDC to pull the "target" frequency down around DC, etc, etc.

--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

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