Re: [Discuss-gnuradio] Setting the DSP frequency in the UHD blocks

[Marcus D. Leech]

In gnu radio companion for a UHD block, how do I set the DSP frequency as well as the RF frequency.  I have done this in my C code which doesn't use gnuradio using the tune_request_t structure.  From the comments in the python code, it appears that there is some way to do it.

I understand that I want to use the DSP LO so that the DC component from the ADC is moved outside the baseband.  Is there a good value or is  anything outside my receive bandwidth is ok?

Is there a reason to use the DSP LO on the transmit side? Does the up conversion happen before or after the DSP LO?

Thanks,
Frank Wallace

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There's a uhd "helper function" that gets imported to allow you to do this:

Where the UHD block takes frequency, you can replace it with:

uhd.tune_request (target_freq, lo_ffset)

The RF upconversion happens after the DSP on the TX side.   It may be beneficial to move the LO on the TX side as well.

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