[Discuss-gnuradio] spurious sidelobes with WBX

[Mathias Coinchon]

Hello,

I am using the USRP1 + WBX to create a DAB OFDM signal (1.5MHz bandwidth) in 
VHF 
band.
The sampling rate used is 3.2MHz (interpolation 40)

However, there's something I don't understand. On the picture attached, you can 
see 2 spurious sidelobs that appear at about 2.5MHz from the center (red arrow).

They are not present when monitoring the spectrum of the baseband IQ signal 
before going to USRP. 

They also don't appear when sending a tone signal.

Is there any explanation for this ? and any hint to avoid or reduce it ?

Thank you for your help.

Mathias Coinchon
opendigitalradio.org

spectrum.jpg
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