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Re: Proposal: SDR-DSP receiver

Hello John and Kaj,
the thing with sampling 144 MHz directly was just meant to be an 
example.. to do it properly one would convert this down to about 10 MHz 
and sample it there, there I agree.

I am certainly interested in your files ( I can handle quite some 
MBytes..:) . What I don't understand up to now how frequency selection 
is made.. with a VCO before sampling or a digital down converter like 
the AD6620 or similar?

73s Achim, DH2VA

John B. Stephensen wrote:

> Hello Achim and Kaj,
> The dynamic range is determied by the level of the signal artifacts produced by
> the ADC and these get worse as the RF frequency goes up. The AD9244 has a 90 dB
> dynamic range when the input signals are limited to 45 MHz. By 240 MHz the
> dynamic range has dropped to 70 dB.
> I was planning to convert the RF to 10.7 MHz and digitize there to get the best
> performance out of the ADC. I've got a partially assembled receiver board with a
> 350MHz 2MHz-wide first IF and an assembled but not yet tested 60-2150MHz LO
> board. Transmitting is easy. You can get quadrature modulator chips for
> 50-3500MHz so all that is needed are baseband I and Q signals. That's why my DSP
> board has two DACs.
> 73,
> John

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