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Re: [Discuss-gnuradio] Cheap ADC at 35MHz

From: Adrian Godwin
Subject: Re: [Discuss-gnuradio] Cheap ADC at 35MHz
Date: Wed, 17 Apr 2002 23:52:17 +0100

Matt Ettus wrote:
> It should be possible to DC-bias the input without losing low frequency info. 
>  Just
> add a fixed, known voltage using a summing amplifier.  No DC-blocking needed.
> The bigger issue is sync.  Do the boards require 15khz sync?  That could be 
> hard to
> inject into your signal...
> Matt

I'm not sure of that yet. It will work to some extent without
(because the test I did was just a sine wave input, and that
captured something) but I don't know how reliable it is -
maybe it's just capturing a few cycles now and then when 
the sync detector gets triggerd by mistake.

It's easy to inject a TV sync : just gate the input 
with a sync signal (and perhaps provide it separately
to the sync input pin). The hard thing is removing the
spurious 15kHz and 50Hz components from the captured
data. However, the predictability of the signals does 
help - it might even be possible to interpolate across
the sync periods to reduce the impact of that part of
the data. 


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