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

From: Jeffrey Lambert
Subject: Re: [Discuss-gnuradio] USRP2 and external RF tuner
Date: Fri, 03 Sep 2010 14:27:43 -0400
User-agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv: Gecko/20100802 Thunderbird/3.1.2

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.


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)

b) with tuner

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 ?


~Jeffrey Lambert, K1VZX

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