About 'internal AGC'

Leif Asbrink leif at sm5bsz.com
Thu Aug 15 03:06:24 UTC 2013


On Wed, 14 Aug 2013 19:55:03 -0700 (PDT)
m240zz at gmail.com wrote:

> yes, I am afraid you are assuming all of us are as smart as you on the 
> topic so if you have time please have another go at it. You are in a 
> unique position to do this since you have all the equpiment at hand.
OK. I will try to make things more clear.

>  The thing that confuses me is why is it during the sweeps due the fft look 
> so different in each of the windows  and it seems like the timing of the 
> sweeps are different.  The sweeps happen at the same time for each dongle, 
> right?  The dongles  are all listening in parallel at the same time?  If 
> so, seems like they would look more alike at the same time.  My apologies 
> for the density on this end.
The dongles suffer from various problems. Overload and inadequate anti-alias 
filtering. A lot of false signals are generated but that is different 
between the different dongles.

The input is identical to all the dongles and you can see that in the beginning
of the video where signal levels are low. At high signal levels they
behave quite differently because false signals dominate (But not in Linrad.)

73

Leif / SM5BSZ




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