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From: root@lando.la.locus.com (The Super User)
Newsgroups: sci.electronics
Subject: Re: Boosting output of a little walkie-talkie
Message-ID: <14290@oolong.la.locus.com>
Date: 2 Aug 90 01:19:49 GMT
References: <3011@media-lab.MEDIA.MIT.EDU>
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In article <3011@media-lab.MEDIA.MIT.EDU> adam@media-lab.MEDIA.MIT.EDU (Adam Glass) writes:
>Could I use a high-frequency op-amp as a voltage follower to amplify
>the output of a little walkie talkie?  I'd like to increase the thing
>to more than 100mW and get enough output out of it to boost the
>effective range up to a mile or two.  Maybe up to 3 or 4 watts.
>
>Is this possible?  Legal?  If it isn't possible, how could I boost the
>signal to increase the range?

    I'm curious why you'd want to use an IC where a single transistor
is appropriate. There aren't may op amps, certainly no affordable op amps,
that do what you want. There are lots of transistors, though, and they
don't cost much. For the rest of this posting, I'll assume you are using
a 49 Mhz FM walkie talkie.

   Normally for FM, a class-C amplifier is desirable, but the low output
of the HT may require a class-A type amplifier. There are many choices of
power transistors; you could use a plentifully available 2N3866 with the
appropriate circuit.

   But, now that I've suggested how, DON'T do this. It is illegal and
inconsiderate. There are many users of the 49Mhz allocation; if you crank
up you power so you can have a 1 mile+ range, you'll also interefere
with people's cordless phones and baby monitors for some distance.

>Also, can the crystals just be desoldered and replaced with different
>frequencies as long as you get crystals of the same type?  Or are
>other things in the circuit tuned to the crystal's frequency?

  Maybe. I've seen a lot of HTs for the 49 Mhz band that have only one
crystal and a synthesizer. Changing the rock can certainly get you some
new channels. In the case that a single channel is provided, you could
change the crystal and probably not have to re-tune anything, since
the HT is fairly broadband (at least across the narrow 49 Mhz allocation).


  What are you trying to accomplish? This may be the wrong approach....