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Re: [Discuss-gnuradio] USRP FLEX900 Daughter Boards Calibration
From: |
Eric Blossom |
Subject: |
Re: [Discuss-gnuradio] USRP FLEX900 Daughter Boards Calibration |
Date: |
Wed, 29 Jul 2009 10:57:35 -0700 |
User-agent: |
Mutt/1.5.18 (2008-05-17) |
On Wed, Jul 29, 2009 at 04:29:35AM -0700, Shabbir Ahmed wrote:
>
> Dear All:
>
> I need to calibrate my USRP with Flex900 daughter boards to take real world
> measurements in dBm. But I am confused with the gain parameter that is used
> in usrp_fft.py.
>
> 1. Not sure whether the RFX900 board has a PGA of its own
The RFX boards have adjustable gain on the Rx side, controlled by
one of the low speed DACs.
> 2. Or is it just the AD9862 PGA before the ADCs
> 3. The gain bar/parameter varies over 0-90, what does this represent?
Roughly the gain in dB relative to an unspecified point.
> 4. When you increase the gain from 0 till 30 or abouts there is no change in
> the noise floor? why is that?
Not sure.
> If you have any docs that I can go through to understand the gain
> characteristic, please.
The code that controls the two parts of the gain setting can be found in
db_flexrf.cc, flexrf_base_rx::set_gain
You might want to add a couple of printfs to that code to see what's
going on.
Eric