From: paulf@umunhum.stanford.edu (Paul Flaherty)
Subject: Re: New licensing system? (Cut down the CW bands!!)
Organization: The Three Packeteers
Date: Fri, 11 Dec 1992 20:51:30 GMT

In article <1992Dec11.160356.23571@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes:
>Using phase coherent techniques, at least 12 db of additional processing
>gain is available to the CW operator. Thus he should be able to operate
>easily in the presence of a 10 db stronger voice signal.

It's arguable that digital signal processing in the ham domain will have
a similar effect on the hobby as did CW over spark.  In as much as these
techniques aren't very prevalant at the moment, though, we have to deal
with the existing equipment.  As techniques such as coherent CW become
cheaper and more popular, it would then be more appropriate to reregulate.

>As to the interference to the voice user, I witnessed a demonstration
>of a new DSP box at a recent hamfest. It was able to notch out several
>CW signals, a couple of dead carriers, and a hetrodyne from a broadcast
>station, all at once. With the unit bypassed and the tape playing, the
>desired signal was unintelligble. With the box in circuit, *all* the
>CW and carriers were gone with only slight clicks still present from
>the CW operators. In addition to that, hum and the random noise floor 
>were sharply reduced. At the flip of a switch it became a CW correlator.
>All this in a little box the size of a Tiny 2 TNC and costing under $200. 
>Truly amazing. Expect to see this technology built in to radios in the
>near future.

I'd be interested to see how such a filter performs on a crowded band; 
specifically what effect it has on ultimate rejection of adjacent channels.

My comment above applies to this argument as well.  Unfortunately, those
rigs that do have this technology "built in" are already out of the price
range of most hams.   The cheap, add on third party DSP box will probably
be the way to go for some time now.  What we really need is a simple box,
with a converter, a DSP chip, a little RAM, some EPROM slots, and some 
trivial I/O (LEDs and switches) that could be sold in kit form for under
$100 -- a cheap DSP testbed.

>I suspect the spectrally efficient claim might be disputed by spread
>spectrum specialists. SS can be as efficient as narrow band techniques
>of the same communications rate, *and* they degrade much more gracefully
>under heavy band loading. They're also more immune to selective fading.

Actually, most of the spectrum efficiency of "spread spectrum" systems
usually comes from the dynamic power control systems associated with
most designs.  In any event, given the International regulatory hassles,
SS on HF in the amateur bands is unlikely anythime soon.

>CW and analog voice can be made to coexist while sharing the same
>frequencies with only the addition of modest and available technologies.
>But the real star is SS. It is mostly immune to the ills of the narrow
>modes, including intentional jamming. The cost to implement it has
>dropped markedly in the last few years. Only archaic regulations and
>inertia prevent it's use on the amateur HF bands.

Rmemeber, that in order to approved internationally, the equipment has
to be cheap, so that most of the ITU nations can monitor what goes on.
At the moment, nobody's producing a cheap commercial SS system for amateur
use.

The trigger price for a piece of add-on gear is somewhere under $200;  if
you expect most amateurs to own such a piece of equipment, make sure it
runs under $150.

Gary, you've basically justified changing the rules in the future, not at
present.

--
-=Paul Flaherty, N9FZX/5W1JX  | "Just name a hero, and I'll prove he's a bum."
->paulf@Stanford.EDU          |  -- Col. Gregory "Pappy" Boyington, USMC (ret)
Newsgroups: rec.radio.amateur.policy