Re: [Discuss-gnuradio] DC Nonexistent Peak at Transmitter

Hi Sema,

You are most likely seeing the local oscillator at the centre due to the WBX being a direct conversion daughterboard:

http://en.wikipedia.org/wiki/Direct-conversion_receiver

To remove this, you can put the following in the center frequency box of the UHD source/sink block in GRC:

uhd.tune_request(uhd_center_freq, rf_freq=(uhd_center_freq+uhd_lo_offset),rf_freq_policy=uhd.tune_request.POLICY_MANUAL)

The 'uhd_center_freq'  and 'uhd_lo_offset' need to be specified. Set 'uhd_lo_offset' to be something like ((samp_rate/2)*1.1).

Regards,

Mike

--
Mike Jameson M0MIK BSc MIET
Ettus Research Technical Support
Email: support@ettus.com
Web: http://www.ettus.com

On Fri, Nov 1, 2013 at 3:21 PM, s k <ofizerof@yahoo.com.tr> wrote:

Hi all,

I am trying to create a complex cosine signal in 100kHz and transmit it with USRP in 110MHz using WBX daughterboard. I have observed this signal in an oscilloscope and a spectrum analyzer. It can be seen that there is a nonexistent peak at transmit frequency of USRP. I also added the related photos to be clear. 

Any help would be kindly appreciated.

Sema

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