Tom,
There is no single answer to your question. The real answer is that it
all depends...
The feedline is only part of the antenna system, and the rest of the
answer depends on the remaining parts of the antenna - length of the
radiator - orientation of the radiator - how the radiator is fed -
influence of surrounding objects. Those are the main factors.
Your transmission line acts as an impedance transformer unless it is
matched with its characteristic impedance at the antenna connection. If
the antenna feedpoint impedance is known, you can use a program like TLW
(available at the ARRL website) to figure the required feedline length
to give whatever desired impedance (near 50 ohms?) at the shack end of
the feedline.
If you do not know the feedpoint impedance of the antenna, then you may
be able to venture a guess by consulting the material in the ARRL
Handbook or ARRL Antenna book or other such sources. It is possible to
calculate the antenna feedpoint impedance by using an antenna modeling
program like EZNEC.
73,
Don W3FPR
T W wrote:
Hi, Group,
Can anyone tell me what length of end-fed line works best on 80M using a KX1
with ATU? I'm having a heck of a time trying to find a length that will work
with 80M and 40, 30 and 20. I know the ATU is not really designed to tune
80M effectively. It would be nice to have one antenna to do all bands, but
if not a separate wire for 80M is okay too.
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