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Re: [Discuss-gnuradio] AGC


From: Matt Ettus
Subject: Re: [Discuss-gnuradio] AGC
Date: Thu, 01 Jun 2006 20:08:17 +0000

> More interestingly, I'm using complex_to_mag to demodulate a 32K sps
> baseband channel as AM, then filtering/decimating the resulting audio.
>
> If I set the AGC reference value (second parameter) to anything above
> 0.2 (including the default 1.0), the audio comes out distorted.  It
> sounds like clipping.
>
> For a reference value, of say, 0.5, complex_to_mag should be outputting
> peaks at |0.5+0.5j| which is ~0.71.

I don't have the agc code in front of me, but the definition of the setpoint in 
important.  Assuming you make the setpoint 1, and that the agc is setting the 
average (of either I or Q) to the setpoint, the amplitude will go from 0 to 2, 
since this is AM.  You will need to subtract 1 so that you get a signal of +/- 
1 for the audio sink.

Matt






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