Re: [Discuss-gnuradio] USRP2 and external RF tuner

[Jeffrey Lambert]

Well, you haven't really provided enough information here.  Assuming 
that your "RF Tuner" consists of some sort of frequency conversion and 
an LO, you should know that you will always have leakage between the LO 
input into the mixer and the IF output.  Perhaps that is what you are 
seeing?  Does your RF Tuner have any sort of filtering?  If the spurious 
signal is on the IF, amplifying it will also amplify the spurious products.

~Jeff

On 9/3/2010 11:45 AM, Luca Pascale wrote:
> Hi Matt,
>
> I have connected the RF tuner that provides (nominal) a gain of 30 dB.
> So the chain is (SIGGEN)--->(TUNER)--->(USRP2).
> The tuner itself introduces spurious signal (below -70dBm).
> The output spectrum is:
>
> a) without tuner (description is above the picture)
> http://imagebin.ca/view/ZTARvXd.html
>
> b) with tuner
> http://imagebin.ca/view/KOYDSsHI.html
>
>
> Do I need more amplification on the IF signal ?
> Or does exist another way to obtain a clear spectrum with the injected
> tone only ?
>
> Is it possible that some spurious are due to the downconvertion process ?
>
> Regards,
> Luca
--
~Jeffrey Lambert, K1VZX