RadioBanter - View Single Post

April 26th 06, 06:54 PM posted to rec.radio.amateur.antenna

wrote:

You can effect the match with either open or shorted stubs when the
dimensions are correct. Performance is not significantly different.

See Mr Cebiks site. He has done a lot of work that is more fact than
lore.

A final note. My attic is a very difficult place to work. There is no
way I can install an antenna and then make numerous adjustments to get
it tuned to the space. I must be able to do any required tuning in my
basement shop or maybe outside on my deck and then take it to the
attic for installation. So for my application, I want something that
is not sensitive to near by objects. The end fed, open stub J-Pole
seems to fit that requirement.

An attic is a problem for many antennas and tuning them is part of it.

One trick I've tried to help others was tune it inside a room and then
note how the SWR changes in location and adjust accordingly.
Tuning in this case was adjusting the length of the longer element
(capped with 1/.4" brass bolt and nut) and stub length without
altering the initial best SWR tap. Usually shortening the longer
element was the needed adjustment.

Allison

Yes, I read Cebik's article on J-Poles several times. I don't doubt
that both designs can be tuned to the same SWR and produce the same
performance. And I tried the brass bolt and nut trick and a coil of
coax at the feed point. But in my basement shop, the shorted stub
copper J-Pole was very, very sensitive to almost any change of
orientation or location. And then everything changed when I installed
it in the attic. But the Arrow open stub J-Pole seemed to produce the
same SWR regardless of orientation or location in my basement or in
the attic.

Anyway, thanks for the insight, jimbo