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TCP-group 1994

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Re: Patents and AX.25

My mailer said WALT DUBOSE - K5YFW said this:
>         The military doesn't have enough satellite channels to
>         support all its communications needs...local or long haul.

Hmmm...  we kept most of the satellites turned off and in standby mode
all the time in case they were needed for something else. There's far
more bandwidth available than needed, but it's just that field units don't 
have a need for satellite links just to talk to a neighbor. If you 
havn't figured it out I was in satellite communications and my specialist
was spread spectrum and communications survivability in nuclear war. 

>         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.

Check the radiation patterns on the antennas sometime. Best bet is to
contact the Navy about it since the Army gets all of it's HF propagation
and antenna radiation patterns form the Navy.  I used to get the MUF
and antenna charts from them every month since all people in CINC jobs
(Commander In Chief  support jobs) had to know how to talk to someone
in any part of the world at any time and know exactly what antenna and
freq to use at that given time.  Since a unit typicaly doesn't want to
talk to someone 4000 miles away, the antennas have a fairly vertical 
radiation pattern. To talk long distance they use a dipole or phased
array verticals. The antennas on the backs of vehicles don't have the same
radiation pattern as a regular amateur radio operator antenna. This
reduces the coverage area. Sure it doesn't put up a border and it can
still make it around the world, but I can hook up a dummy load here and
if enough signal makes it to the ionosphere it can be heard around the
world too. 

I often wondered if hams have done any experimenting with different 
radiation patterns besides 'horizontal' to change their coverage on
HF and make it more stable to neighboring states and not be so affected
by the ionosphere. The Navy has this down to an art and they know how
to maintain constant communications with someone only a few hundred 
miles awy or so using HF.  But being ham radio operators we always want
to talk to the 'farthest person away' when it comes to HF  :-)

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

That's because theres no need for field units to use spread spectrum. It's
used mainly to keep communications up between Commander-in-Chiefs, ships,
and airborne command posts.  Plus they typically don't give things like
crypto equipment and anti-jam modems (spread spectrum units) to field units
and then stick them in enemy territory. 

> 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.

And we were passing real-time digital video over satellites and had fiber
optic patch bays and we were still complaining :-) 


Ron Atkinson  N8FOW

AMPRnet  : n8fow@n8fow.ampr.org
Internet : ron@chaos.eng.wayne.edu

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