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From: "Vernall" <vernall@xtra.co.nz>
To: rsgb_lf_group@blacksheep.org
References: <65AECDF1F89AD411900400508BFC869F9C047B@pdw-mail-1.dera.gov.uk>
Subject: LF: Re: RE: <Tech> Wolf coding
Date: Wed, 2 May 2001 08:35:45 +1200
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Andy and others,


> re Jim's comments :
>
> >
> >  I have been thinking along similar
> > lines for somewhat different reasons. I don't claim to have
> > expertise in this field, but suppose the data rate of Wolf was
> > reduced by a factor of 10, ie, to 1 bit per second. What would be
> > the effects?
> >
> I was not proposing just slowing Wolf down, I was arguing the merits of
> using Uncoded BPSK for the same performance  (a-la VE2IQ & Coherent) but
> at 1 b/s - this would give a few extra dB capability immediately.  With
> Wolf coding as well, this could give 10 dB extra but at 16 minutes for a
> 15 character message.

I suggest that there are also middle options.  At LF there are "lightning
pops" and some forms of QRM that are that are "bursty", and either could
thwart successful decoding of a few parts of a message, but inbetween noise
bursts the RF S/N conditions could be satisfactory for reception.  So having
some redundancy is desirable, especially for a text messaging system.  The
question is in the selection of the degree of coding overhead.  I do not
have a suggestion as to where the optimum answer lies.

73, Bob ZL2CA