Sonny Hood wrote:

I have an antenna that needs 100 ohm twin lead to match the impedance
of the feed point. The 450 ohm lead has messed up the match and
screwed up the resonance, does anone know of such an animal?

Let's take a look at how the 450 ohm feedline "messed up the
match". The SWR on the 450 ohm feedline will be 450/100 = 4.5:1.
A feedline length equal to a multiple of 1/4WLs will transform
the 100 ohms to ~2000 ohms or a 50 ohm SWR of 40:1 which is
probably out of the matching range for built-in autotuners, for
instance. You can change the impedance seen at the tuner back
to 100 ohms by adding or subtracting 1/4WL of 450 ohm line which
will make it a multiple of 1/2WL.

As someone else said, one of the most common ways to match a
100 ohm antenna is to use 1/4WL of 75 ohm coax and then 50
ohm coax the rest of the way. Instead of "messing up the match",
it fixes up the match. The SWR on 75 ohm coax would be 100/75 =
1.33:1. The impedance at the end of the 1/4WL matching section
would be 75/1.33 = ~56 ohms, a good match to 50 ohm coax.

If you are wanting to use the antenna for multi-band operation,
change the length of the 450 ohm line until the match is not
"messed up".
--
73, Cecil http://www.qsl.net/w5dxp