[Elecraft] Re: T1 tuner issue

[Trevor Day]

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 <20051026035155.18357.qmail at web30405.mail.mud.yahoo.com>, 
Kurt Loken <ae6uj at yahoo.com> 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