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

From: Josh Blum
Subject: Re: [Discuss-gnuradio] How to capture the Rx data using uhd_rx_cfile and agree with the uhd_fft Scope mode data
Date: Fri, 28 Sep 2012 17:03:37 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120827 Thunderbird/15.0

On 09/28/2012 04:34 PM, LD Zhang wrote:
> I looked and ran the attached GRC file. It does work. I have a question on
> whether the slider gain is applied before or after the ADC?

The set_gain call applies to all gain elements on the RF frontend and in
the ADC. In this case, when using LFRX + N210, set_gain only adjusts 6dB
of digital gain in the ADC itself.


> LD
> On Fri, Sep 28, 2012 at 3:28 PM, Josh Blum <address@hidden> wrote:
>> On 09/27/2012 02:42 PM, LD Zhang wrote:
>>> 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.
>> You are correct. The N210 has a 6db digital gain. Attached is a GRC
>> flowgraph that loopsback TX and RX with Basic daguhterboards. You can
>> see the digital gain slider in action.
>> The gain parameter in the GRC block is a amalgamation of ADC and RF
>> frontend gain elements. The API also allows for individual control, but
>> this level of control is not available in the GRC gain parameter.

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