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Re: Going Digital... Ham Radio?



This months QEX has an excellent writeup about G4GUO's system, and
some insight also by Doug Smith about digital systems.  Another interesting 
point is that according to the ARRL after contacting the FCC-- the FCC is 
going to allow this modem on the HF Phone bands,
because supposedly it "is not data" and is "digital telephony" covered 
already as one of the allowed Phone emission types.  I think that is
a stretch personally, but it emphasizes the willingness of the FCC to
let us experiment with new technology-- and recoginition that the
digital and analog domain is starting to legally blur...

I think the issue is "May/June 2000"... Charles' system uses an AMBE voice 
encoder chip to run a 36 tone modem on a Motorola 56002 EVM.  It
is a good starting point-- getting rid of the AMBE chip, and porting
the code over to PC/Soundcard is possible-- but would be a LOT of work.  A 
good "halfway" point would be just to port the modem over to
a PC/Soundcard program, and still use the AMBE board.

In the case of satellites, other types of modems might be better for this 
use-- as the parallel tone modem is set for the types of multipath and fades 
that are typical on HF.  We shouldn't get these
on sats, but the doppler would be a big problem instead.

Anyway, as it stands, the 36-tone modem is a clever re-implentation of the 
military 39-tone modem that is ompatible with the narrower bandwidth ham IF 
filters.

Fred W0FMS

>From: Cliff Buttschardt <cbuttsch@slonet.org>
>To: "Frederick M. Spinner" <fspinner@hotmail.com>
>Subject: Re: [amsat-bb] Going Digital... Ham Radio?
>Date: Wed, 07 Jun 2000 20:52:35 +0000
>
>
>Hi Fred.  I agree with you regarding Jon's comments but it
>seems that digital voice has to be the way to go for the
>"modern" ham.  I've not seen any reasonable reference to voice
>modes using digital.  Has anything been written in the ham
>publications on this?  Cliff K7RR
>
>
>"Frederick M. Spinner" wrote:
>
> > "New" ham modes such as Charles Brain's Digital voice would be an
> > absolute shoe in on 3D-- and should be encouraged on the birds.
> >
> >

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