Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!att!tsdiag!davet
From: davet@tsdiag.ccur.com (Dave Tiller N2KAU)
Newsgroups: sci.electronics
Subject: Re: Boosting output of a little walkie-talkie
Message-ID: <1063@tsdiag.ccur.com>
Date: 8 Aug 90 15:00:49 GMT
References: <90080614412836@masnet.uucp> <1990Aug7.182544.7140@ns.network.com>
Organization: Concurrent Computer Corp. Oceanport NJ
Lines: 24

In article <1990Aug7.182544.7140@ns.network.com> logajan@ns.network.com (John Logajan) writes:
-peter.saulesleja@f630.n250.z1.fidonet.org (peter saulesleja) writes:
->Why high current?  There is very little current travelling through 
->the antenna, so you'd require a higher voltage, wouldnt you?  After 
->all, P=VI...  And air is a very good insulator.   A high current would 
->be impossible, at reasonable  (below 1,000,000 Volts) voltages.
-
-The impedance of the antenna/radio wave interface is generally on the
-order of 50-300 ohms.  Given this "resistance" you can come up with
-the voltages needed for a given power.  For simplicity, to drive one
-watt into a 100 ohm load would require 10 volts.
-
At 100 mA.  Find an op-amp that can deliver 100 mA at a 10 V p-p at 27 MHz.
Mercy, what a slew rate!  As for using a high voltage, remember that this
thing is battery supplied, and that the antenna is waving around at people.
I wouldn't want to see high RF voltage flying around my head from an exposed
antenna.  The easiest method, if it were legal, would be to use a final
transistor current amp (common collector).  There are lots of transistors 
that'll handle 27 MHz just fine.
-- 
David E. Tiller         davet@tsdiag.ccur.com  | Concurrent Computer Corp.
FAX:  201-870-5952      Ph: (201) 870-4119 (w) | 2 Crescent Place, M/S 117
UUCP: ucbvax!rutgers!petsd!tsdiag!davet        | Oceanport NJ, 07757
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