Path: utzoo!mnetor!uunet!husc6!mailrus!ames!pasteur!ucbvax!hplabs!sdcrdcf!trwrb!trwind!johng
From: johng@trwind.UUCP (John Greene)
Newsgroups: sci.electronics
Subject: Re: Radio booster
Message-ID: <392@trwind.UUCP>
Date: 6 May 88 16:06:37 GMT
References: <845@imagine.PAWL.RPI.EDU>
Reply-To: johng@trwind.UUCP (John Greene)
Organization: TRW Information Networks Div
Lines: 34

In article <845@imagine.PAWL.RPI.EDU> snyderw@pawl22.pawl.rpi.edu (Wilson P. Snyder II) writes:
>
>	I am a member of a club which uses Radio Shack headset walkie-talkies.
>We are having a problem with the range of these units, so I replaced the
>antenna with a longer, common wire which runs through several rooms.  Now,
>the problem is that this decreased the antenna gain, so now I need to boost
>the power output of the radio.  I assume that the radio was at the 100mw
>FCC limit (47 MHz), but since the antenna is now less eficient, boosting
>should be possible.
>	So, what I am interested in is a small 9Vdc circut to boost the
>radiated antenna power.  Thanks.
>
>
If the antenna is less efficient now than it was before, why change it???


I think your problem is not a less efficient antenna, but a terrible 
impedance mismatch you introduced with the long wire.  The radio is designed
to have maximum gain using a 50 ohm load at the antenna, anything else is
going to result in standing waves which means more power dissipated in the
radio than radiated to the air.

There are several ways to increase the gain of an antenna by it constuction.
The easiest to implement would be to make a dipole of the proper length for
47 MHz.  This may be all that you need.  I don't remember the correction factor
for calculating the wavelength in air but I'm sure you can find it in the 
library or someone on the net may have it handy to post.  A properly constructed
antenna may be all that you need.

-- 
John E. Greene    "People are just like frankfurters....You have to decide
                   if you're going to be a hot dog or just another wiener" DLR
TRW Information Networks Division 23800 Hawthorne Blvd, Torrance CA 90505
ARPA: johng@trwind.ind.TRW.COM  USENET: ..trwrb!trwind!johng