Re: [Discuss-gnuradio] Carrier leakage on transmit

[Charles Brain]

Hi Johnathan,

You can offset the carrier with UHD by passing a 2nd parameter
in the set_tx_freq call. Unfortunately it only seems to work with 
small offsets, far too small to take it outside the passband of my
signal. :-(  It was not so much of a problem with my DVB-S code
but I am now playing with DVB-T and I can see it in the middle 
of the  ODFM waveform swamping the pilot tones. 
I think some form of calibration routine is going to be necessary.
I guess I will just have to be patient and wait.

- Charles

----- Original Message ----- 
From: "Johnathan Corgan" <address@hidden>

> 'set_lo_offset', which will adjust the analog LO in frequency and

> to your desired tuned frequency.  I'm not sure what the equivalent
> function in the UHD is; it may not be implemented yet.
>
> This at least lets you move the spurious carrier outside the passband
> of your transmit signal. In order to fully remove it, either DC offset
> trimming would need to be implemented in the FPGA, or host
> code/firmware written to tweak the built-in DAC DC offset
> compensation.  I've done the former for clients, and it works well.
>
> Johnathan