Topband: Analog to Digital converter for 1.8MHz

CHARLES HUTTON charlesh3 at
Fri Jul 2 15:03:49 EDT 2004

I'm not sure I agree with this. The contributors to close spaced dynamic 
range are the inherent dynamic range of the system and selectivity that will 
discriminate against interference.

DSP filtering can easily produce selectivity as good or better than the 
mechanical or crystal filters we use. The controlling factor for DR then 
becomes the A/D converter.

I'd re-write this to say "good luck doing this with a A/D and DSP system 
instead of an analog front end and IF".

By the way, there are some 18 bit ADC's with spurious free dynamic range in 
excess of 103 dB and sampling rates of over 1 MSPS. For 455 kHz IF's, they 
would provide a fine A/D conversion that should meet even our most demanding 


>From: "Tom Rauch" <w8ji at>
>Reply-To: Tom Rauch <w8ji at>
>To: "Richard (Rick) Karlquist (N6RK)" <richard at>,"Steve 
>Ireland" <sire at>, <topband at>
>Subject: Re: Topband: Analog to Digital converter for 1.8MHz
>Date: Fri, 2 Jul 2004 13:45:58 -0400
>I'm sure the target value would be different in different
>areas of the world and even different areas of the United
>States, but domestically (and I suspect in Europe and Japan)
>80-90dB close spaced and 90-95dB wide spaced would be enough
>for almost any location. Good luck doing that with a DSP
>system instead of a crystal or mechanical filter!
>73 Tom
>Topband mailing list
>Topband at

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