Hi, I always get a strong spike in the attachment, when using uhd_fft to measure the noise. Please note there is no any signal on the air, only noise, but I got this spike. I guess this is the so called DC component. Thus I tried to remove this spike, as stated in http://files.ettus.com/uhd_docs/manual/html/general.html#tuning-notes, using the advanced tuning request.
My sample rate is 2Ms, so as my understanding, I need to set the lo_offset
as >= 4MHz, to get the spike out my band, like this:
tune_req = uhd.tune_request(options.freq, 5e6) # with lo_offset =
5MHz
usrp.set_center_freq(tune_req, 0)
Then I get the tune result as:
Tune Result:
Target RF Freq: 2405.000000 (MHz)
Actual RF Freq: 2405.000000 (MHz)
Target DSP Freq: 5.000000 (MHz)
Actual DSP Freq: 5.000000 (MHz)
However, the spike is still there, almost the same, and the center
frequency is even still the same (this could be due to the some GUI usage)!
I really don't know if the advanced tuning works or not. It seems that the
incoming streaming still contains the DC component.
Spike of the received noise.
[image: Inline image 1]
<<image.png>>
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