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Re: [Discuss-gnuradio] How to capture the Rx data using uhd_rx_cfile and

From: LD Zhang
Subject: Re: [Discuss-gnuradio] How to capture the Rx data using uhd_rx_cfile and agree with the uhd_fft Scope mode data
Date: Thu, 27 Sep 2012 14:42:43 -0700

Yes. I can understand the LFRX does not have any adjustable gain. But what comes out of the USRP source should be samples already digitized. Surely there is gain to be adjusted before the ADC. According what I see, it is from 0 to 6dB (in voltage?). I don't see how this can be inserted into the USRP source block.

Also I have some related questions:
1. the float numbers out of the USRP source block appear to be in volts. There is no indication of what units it is in.
2. Is there any way of specifying bandpass filters before the ADC? This would probably be independent of the LFRX, but something on the motherboard before the ADC? I do see an option in the USRP block that seem to do this. However this bandpass may be after the ADC?



On Wed, Sep 26, 2012 at 11:55 AM, Josh Blum <address@hidden> wrote:

On 09/26/2012 01:36 AM, LD Zhang wrote:
> Hi,
> I did try and made a GRC example of using a USRP Source and a fft sink,
> scope sink, and a file sink to test out the idea.
> When looking at the scope sink, the data is about +/- 2x10^-4. I changed
> the gain of the USRP source block to 20 dB. But nothing happened to the
> signal amplitude. How is this possible?

You mentioned LFRX? There are no configurable gain elements for the LFRX

If this helps, the various gain ranges are listed for various
daughterboard frontends here:


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