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TCP-group 1994


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Re: Patents and AX.25



In Ron's message of 20 Dec 1994 at 2301 EST, he writes:
> My mailer said John Paul Morrison said this:
> >
> > I'd never thought about the military still using HF, with today's
> > satellites and everything. Guess I shouldn't be surprised that the
> > military is paranoid enough to keep every option open, ie "what if
> > nuclear mines are detonated in space, wiping out all our birds" or
> > perhaps "we'll detonate nuclear mines in space FIRST, cripple
> > EVERYTHING, and then gain the tactical advantage with our spiffy
> > mil-spec HF radios!!!"

        The military doesn't have enough satellite channels to
        support all its communications needs...local or long haul.

>
> HF is used mostly for local stuff.  They use high radiation antennas
> that effectively makes HF covers a very small area of maybe a few
> hundred miles, depending on the type of antenna being used.  All depends
> on the mission actually, but your normal everyday tactical unit doesn't
> run antennas with horizontal radiation patterns.  This gives more coverage
> than VHF/UHF can but it won't  go around the world. For some reason hams
> just havn't learned to do this yet.

        You need to define local...but actually HF is used for the
        under 750-1200 mile range more than 0-30 miles.  HF is also
        good for this (local) as its hard to put up a mobile 300ft
        tower in the battle field.

        Fixed/portable stations use a number of NVIS antennas and
        mobiles fold over their 16 & 32 ft whips so they will have
        NVIS radiation patterns.

        Take a long Bug Catcher and tie the end to the front bumper
        and see if you can't talk to stations within a 100 mile radius
        where if the antenna is vertical, the closest station is
        generally 100 miles away.


>
> Spread spectrum with mitigation (frequency hop a direct sequence spread
> spectrum signal) and FEC is not affected by a nuclear explosion in the
> atmosphere that would normally 'shut off' the other bands (in case
> you're interested :-)  The military went to spread spectrum not only
> due to message privacy capabilities, but also because you can basically
> drop a bomb and destroy the atmosphere and spread spectrum can still
> operate. Something else hams havn't seemed to figure out yet, they still
> think CW is going to cut through when it won't.

        During Desert Shield/Storm there were 100 times more plain
        vanilla HF SSB stations on the air than spread spectrum stuff.


Walt DuBose/K5YFW, USAFRes Retired
Former Chief of Comm. Maint.
Theater Aeromedical Evacuation System
Saudi Arabia, Desert Shield

PS, I retired in discuss because Aeromedical Evacuation System
wouldn't change from using a Bell 103 modem at 300 baud on HF rather
than a "real" HF modem format.




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