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From: karn@petrus.UUCP (Phil R. Karn)
Newsgroups: net.ham-radio
Subject: Re: Proposal (LONG!!!)
Message-ID: <791@petrus.UUCP>
Date: Fri, 3-Jan-86 16:10:12 EST
Article-I.D.: petrus.791
Posted: Fri Jan  3 16:10:12 1986
Date-Received: Sat, 4-Jan-86 05:45:42 EST
References: <-27771447@techsup>
Organization: Bell Communications Research, Inc
Lines: 36

What follows are my initial reactions to the Stoner proposal for creation
of a Public Digital Radio Service.  Since I do not have access to Compuserve,
I'd appreciate it if somebody forwarded this note to Don Stoner.

I agree that the time has come for such a service. As involved as I am in
the development of amateur packet radio, I can see plenty of legitimate
applications for low cost, personal digital radio communications that
properly lie outside the scope of the Amateur Service (e.g., business use,
need for encryption, etc). Further, the need for such a service is enhanced
by the amateur community's continuing opposition to any form of "no code"
license, an irrational attitude that will surely prevent packet radio from
ever reaching its full potential in the Amateur Service.

Having said this, however, I must take issue with the details of Stoner's
proposal, in particular his frequency and bandwidth recommendations. As a
radio amateur, I instinctively resist the "giving away" of any amateur
allocation, even one as lightly used as 52-54 Mhz. I am also not convinced by
Stoner's contention that an inexpensive radio modem, particularly one with
an emission bandwidth of 2 megahertz, could be operated without interference
to nearby TV receivers tuned to Channel 2. At the very least, I would like
to see the results of any tests he has conducted to reach this conclusion.

Another problem I forsee with such a large allocation, which apparently would
be used for a single, wideband RF channel, is multipath dispersion.
The DARPA packet radio community has found that packet radios operating
in a typical urban or suburban environment are effectively limited to
data rates of 100 to 400 kilobaud because of the intersymbol interference
caused by multipath propagation effects. Only when a strong line-of-sight
signal component fully captures the receiver is it possible to operate at
higher speeds. Therefore, it is clearly not necessary to allocate such a wide
portion of spectrum if the intent is only to provide a single RF channel.

I think that Mr. Stoner's proposal would be an excellent one once he finds
another, smaller, piece of spectrum outside the amateur bands to use.

Phil Karn, KA9Q