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echo: scanners
to: ALL
from: SCOTT HOFFMAN
date: 1996-08-13 08:52:00
subject: Impedance Mismatch

I just bought a new antenna (which is meant for FM radio) but I use
it for my scanner anyway and it seems to work pretty good. Although I
am concerned about impedance mismatches and the fact that I might not
be working my antenna to its full potential because if this..
My problem is... that the antanna comes with a 'built in' set of
twin-lead cables (which is labled 300Ohms).. My problem is how
do I Interface 300 Ohms to 50Ohms which most scanners use?  I know
that their are plenty of  300 --> 75Ohm transformers which are
used for TV's,  but I have NEVER ever seen a 300 --> 50Ohm transformer,
does on even exist?  where can I get one?    So what I'm using now
is just a 300-->75 transofrmer and I'm inputting the 75Ohm into
my scanner..  Does feeding the 75 Ohm input into the 50Ohm scanner
input really make "that much" of a difference or is the difference
pretty much minimul almost non-existant?   One last question..
Are antennas really 300 Ohms, I'm not sure I get this concept.. Couldnt
I just splice my low-loss RG-8 50Ohm cable right onto the antenna
without even using a 300-->75/50Ohm transofrmer?
--- GEcho 1.00
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* Origin: þ Brian's World (516)-331-5540 Long Island, NY þ (1:2619/232)

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