Topband: Analog to Digital converter for 1.8MHz
charlesh3 at msn.com
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 contesting.com>
>Reply-To: Tom Rauch <w8ji at contesting.com>
>To: "Richard (Rick) Karlquist (N6RK)" <richard at karlquist.com>,"Steve
>Ireland" <sire at iinet.net.au>, <topband at contesting.com>
>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!
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