Mike Coslo wrote:
Mike Burch wrote:

I have recently built a J pole for 2 meters from the handbook and I
was wondering if any of you had some tuning tips.



I just put mine up this past weekend. I made a Jpole out of 3/4 inch
copper pipe. My coax is attached with copper pipe clamps. To tune, I
used a MFJ antenna analyzer, but anything you have that measures SWR
will be okay.

As I moved the clamps up or down on the antenna, I could tune the SWR &
resonance pretty easily. Biggest problem was having to walk away from
the antenna (on the roof) to keep from affecting the readings. Tuned it
for 1:1 on my favorite repeater frequency which happens to be in th
emiddle of the band, and have less than 1.5:1 at the edges. The antenna
works very well compared with the homebrew 1/4 wave ground plane I had
before.

The clamps are supposed to move up and down equally on the antenna,
but the position that gave me the best resonance and SWR hade the
braided wire clamp just a tad below the center conductor clamp, so that
may be another area for adjustment.


BTW, I have seen some plans for a Jpole identical to the one I built,
and they call for several turns of coax as a balun for the thing. I
really don't think that is needed. I measured out 1.1:1 SWR @ 50 ohms in
the middle, and good SWR across the band.

Then again, maybe there are some hams that put a balun on everything! ;^)

- mike KB3EIA -