Donnie,



The "open end" of the matching section of the J antenna (commonly called a
"J-Pole"), as you have found, does have a large effect on the
characteristics. The spacing of the two parallel lines or pipes changes the
match. I think that to the first approximation, this is an acceptable way
to adjust the match. The only problem I can foresee is that the top of the
shorter line/pipe is at a high impedance point and any changes there would
cause changes---such as dirt build up over time or deterioration of the PVC.
I would tend to put it a little ways down from the top to head off such
concerns. I recent built a J antenna for 1296 MHz and used a small piece of
plastic in this location for tuning it.


--
Steve N, K,9;d, c. i My email has no u's.

"Donnie B" wrote in message
...
I recently built a two meter j-pole.In the plan, I saw no mention of pvc
use.Yet, I had to place a piece of pvc between the two uprights to get
the swr to fall.Is there something I missed?
....