One other thing worth noting Kurt is that when you use a tuner at the tx
end of a coaxial (unbalanced) feedline, then the feedline itself becomes
a radiating part of the antenna system. The ATU will hopefully reduce
the SWR on the line between the transmitter and the ATU, but it will not
change the SWR present on the feedline.
If you use a balanced feeder such as twin or preferably open wire, then
although the SWR on the feeder may be high, it is balanced and in a
perfect world the feeder will not radiate.
The likely outcome when using an ATU at the tx end of the feeder is:
Coax
Possible high SWR on feeder, feeder is unbalanced and will radiate and
also receive unwanted signals (any rf generating device in the house).
Possible TVI/BCI. Altered radiation pattern (usually for the worse)
Open wire
Possible high SWR on feeder, feeder is balanced and radiation (incoming
or outgoing) will be minimised reducing unwanted interference both ways.
Pattern remains predictable within usual constraints. Your RF gets to
where it is needed most, up in the air :-)
My advice is to leave the top section of your dipole as it is and to
replace the feeder with open wire or at least twin. It should be an
improvement on all bands.
HTH
Trev G3ZYY
In message <[EMAIL PROTECTED]>,
Kurt Loken <[EMAIL PROTECTED]> writes
Hello All,
Thanks to everyone who responded. I received a lot of
interesting suggestions that should be fun to
experiment on. My final solution will probably be to
add some additional elements on my current dipole for
20m...but it might be fun to fool around with the feed
lines a bit before then.
Thanks for the education. I think it is time for me
to crack and antenna book and read it though.
Regards,
Kurt - ae6uj
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--
Trevor Day
UKSMG #217
www.uksmg.org
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