Re: [Discuss-gnuradio] Questions about WBX daugtherboard

[John Orlando]

> Hi,
> I forgot to thank you for your answers. So... thank you !
> Concerning the spurs, they are peaks at precise frequencies. Their position
> and their strength depends on the LO frequency  (I observe peaks around 698
> MHz but not around 714 MHz as an example) but not on the decim rate. I
> observed also an attenuation around the central frequency when I use LO freq
> above 1 GHz. Note that the usrp2 is used without its top (i don't know if
> this precision has any importance)
> I'm not really clear and i can add prints screen if desired.

Are you seeing spurs at harmonics of the USRP2's on-board 100 MHz
reference?  In other words, if you tune your USRP2 + WBX to 501 MHz,
601 MHz, 701 MHz, etc., do you see the spurs that you're referencing?
The 1 MHz offset is so that the DC offset correction doesn't come into
play.

The ADF4350 used on the WBX does produce some spurious content, but
they are typically low-level (-60 dBc or lower from my experience).
The loop filter on the WBX is fairly narrow, so this should help
remove spurs on the LO.

If you can provide any additional information on the spurs you're
seeing (screenshots of usrp2_fft.py would possibly be helpful), it may
help diagnose what's going on.

-- 
Regards,
John Orlando
CEO/System Architect
Epiq Solutions
www.epiq-solutions.com