SH>I just bought a new antenna (which is meant for FM radio) but I use
SH>it for my scanner anyway and it seems to work pretty good. Although I
SH>am concerned about impedance mismatches and the fact that I might not
SH>be working my antenna to its full potential because if this..
SH>My problem is... that the antanna comes with a 'built in' set of
SH>twin-lead cables (which is labled 300Ohms).. My problem is how
SH>do I Interface 300 Ohms to 50Ohms which most scanners use?  I know
SH>is just a 300-->75 transofrmer and I'm inputting the 75Ohm into
SH>my scanner..  Does feeding the 75 Ohm input into the 50Ohm scanner
SH>input really make "that much" of a difference or is the difference
SH>pretty much minimul almost non-existant?   One last question..
Antenna impedance is the stated value only over a range of frequencies
the antenna is designed for .  When you use the FM antenna outside the
range of about 88 to 100 mhz it will no longer be 300 ohms and probably
not 300 even over that large of range.  For receiving, it usually makes
no noticable difference to many users.  There is just too large of a
frequency range to hold the given value.  I would try using a 75 to 300
ohm balun mainly because it converts the twinlead to coaxial cable.  You
probably won't notice much difference if you just connected directly.
If the arangement is used for transmitting, then all bets are off and
the impedance makes a big differenace.
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