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[hfsig] Re: [Flexradio] The final nail in the coffin of Morse ?

DuBose Walt Civ AETC CONS/LGCA Walt.DuBose at RANDOLPH.AF.MIL
Fri Jul 22 15:46:20 UTC 2005


Ant,

I agree that we should look carefully at what DRM and other digital voice
modes are doing and advance the art in ham radio.  DRM and the other digital
voice modes being used by hams today aren't particularly robust...they take
quite a large SNR to produce a good, clean sounding signal.  When used at
low SNRs (weak signals levels) there quality and performance is poor and the
overall communications quality is not much better than SSB.

To make them more robust, considering that they all use OFDM types of
modulation, the best way to make them more robust is to increase the number
of tones and use this increased throughput capacity for heaver FEC.

However, with a 3.5 KHz bandwidth limit being recommended by the ARRL, this
just isn't going to happen.

Walt/K5YFW

PS we've migrated from CW to bandwidth and perhaps now to Digital Voice as
the subject of this thread.

-----Original Message-----
From: hfsig-bounces at lists.tapr.org
[mailto:hfsig-bounces at lists.tapr.org]On Behalf Of
Anthony.N.Martin at seleniacomms.com
Sent: Friday, July 22, 2005 10:28 AM
To: TAPR HF Modes SIG Mailing List
Subject: RE: [hfsig] Re: [Flexradio] The final nail in the coffin of
Morse ?

9kHz AM is the standard for shortwave broadcast AM and in
theory gives us compatability with the sets SWLs use.

Broadcast SSB never took off, although it looks like change may
be happening with DRM.

There is an arguament that amateur digital voice should also aim
to retain compatability with SWL's receivers.

The DRM standards allow several bandwidths, not just 9kHz.

SWLs form some part of the membership of amateur radio societies.
They are also a source of future amateur operators.
Building and operating receivers is a perfectly valid form of amateur
radio that doesn't need a licence and is the only choice in countries
where licences are impossible to aquire.

Ant M1FDE

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