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From: morganh@shazam.WV.TEK.COM (Morgan Hall)
Newsgroups: sci.electronics
Subject: Communications Project
Message-ID: <4979@orca.WV.TEK.COM>
Date: 16 Oct 89 15:15:07 GMT
Sender: nobody@orca.WV.TEK.COM
Reply-To: morganh@shazam.WV.TEK.COM (Morgan Hall)
Distribution: usa
Organization: Tektronix, Inc., Wilsonville, OR
Lines: 34

I have a need -- one that looks like it might make an interesting project for
the winter.  I'm tossing it out to the great minds on sci.electronics
because I tend to think just far enough to get an idea, then ZAP! the
blinders come down and I'm chasing the details of THAT project.  Hopefully,
someone else may think up a more elegant solution...

The need -- cheap, reliable, wireless communication for about 2 days a year.
I breed and show cats.  Our club puts on one two-day show every year.  The
format of a cat show consists of four independent judging rings who must 
communicate back to an announcer.  The announcer then uses a (rented)
PA system to call up cats to a particular judging ring.

We've tried hand-held CB's -- the local chatter makes them useless.  Phones
would work, but rental halls aren't necessarily good places to be stringing
the wires (and in some they're prohibited).  Whatever we use must be 
battery powered, as show halls normally don't have electrical outlets where
you want them.

The lo-tech solution is an alert announcer, hand signals, number cards,
a pair of opera glasses, and lots of mistakes.

Some thoughts are -- the cheap little FM mikes that snap on a 9-V battery
(would they hold frequency stability, and could we tune them to the same
frequency?) and a portable FM radio on an unused frequency.  "Toy" walkie-
talkies (isn't there a 40 Mhz version?).  Infra Red communications -- 
what about FM modulation an IR source at a fairly high frequency, then
decoding with a PLL?  Ultrasonics don't seem like a good idea, as cats can
hear quite high frequencies.

Off-the-shelf solutions generally are too expensive for a two-day show.
If I build something, I'll be concerned with ruggedness and reliablilty
as well as adequate range.

Suggestions?