[Hackrf-dev] Signal Spikes and Jumping

[ryan]

I'm seeing some of the same things as Russell posted a while back and figured I should document similar issues using different front ends (Gqrx) and platforms (OSX).

I'm seeing strong signal spikes at very round numbered frequencies (i.e. 800mhz, 850mhz, 900mhz, screenshot in gqrx: http://imgur.com/wRP5ScX,PBZKnN2#0 and in gnu radio-companion http://imgur.com/wRP5ScX,PBZKnN2#1)  and also at seemingly random places in the spectrum (see vimeo link below).   Could this be a firmware/hardware bug? an anomaly that all SDR hardware possesses? PEBKAC?

It's worth noting that these strong spikes seem to appear and disappear depending on the hardware frequency and sample rate.  An example here http://imgur.com/OnvdPX2,4c9lE14 shows a huge spike that disappears after starting and stopping the radio and chaining the sample rate, as illustrated here http://imgur.com/OnvdPX2,4c9lE14#1.

Also I've seen some glitchy tuning behavior similar to what was previously mentioned by Russell.  An example of both issues is at https://vimeo.com/71824106.  Note that this video was recorded with no antenna plugged in and the PCB antenna trace cut.  This leads me to believe that the huge spike you see is not a real over-the-air signal.

I'm running the newest libhackrf from git.  Other system info:

System: Mac OS X 10.8.4
Firmware/Hardware:
$ hackrf_info
Found HackRF board.
Board ID Number: 1 (Jawbreaker)
Firmware Version: 2013.07.1
Part ID Number: 0xbc6c474c 0xbc6c474c

-Ryan
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