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[Discuss-gnuradio] FPGA Gain?

From: Eric Cottrell
Subject: [Discuss-gnuradio] FPGA Gain?
Date: Tue, 10 Jul 2007 16:13:17 -0400 (EDT)


The LFRX daughterboard on the USRP has 20 dB of gain.  I seem to remember that 
10 dB of that gain is from the FPGA.  I assume that this gain is after the ADC? 
 If so, is it really useful?

I relate digital gain to zoom on a digital camera.  The analog gain is the 
optical zoom and the digital gain is the digital zoom.  Digital cameras have 
10x or more digital zoom but it is not really useful.  At high digital zooms 
you get lower resolution and the picture is blocky.  Optical zoom is more 
useful as it comes before the digitizer.

So if I have noise values of 35 and signal values of 40 then I get values of 
350 and 400 after the 10 dB digital amplifier.  I may see a higher amplitude 
signal but how do I gain anything?  Am I missing something?

73 Eric

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