On Sunday, February 16, 2014 11:12:51 AM UTC-6, Jeff Liebermann wrote:
On Sun, 16 Feb 2014 06:32:38 -0800 (PST), W5DXP

wrote:



On Saturday, February 15, 2014 9:58:10 PM UTC-6, Jeff Liebermann wrote:

However, a J-pole (or Zepp) is not a 1/2 wave antenna. The driven

element is a 1/4 wavelength long, and therefore DOES require a ground

plane.



Sorry, that is not correct.



Agreed. See my followup to my posting where I noticed that I've been

building J-pole antennas with the coax feed connected to the wrong

element. Judging by some of the photos I've found, I'm not alone.


I never built J-poles myself. Never was that fond of the design
for some reason. I always preferred the "ringo" method of feeding
a base fed half wave. IE: a flat single turn tapped coil, and coax
capacitor. I used them on 10m mostly. They work decently well in
most cases with no decoupling section. But they work even better
with decoupling. I used a 1/4 wave length of coax to a union which
was attached to the mast, and had a set of three radials.

But... The 5/8 ground planes were always better than the 1/2 waves
on distant 10m local stations. Even the decoupled version.
And being low angle space wave stuff, it's a pretty good test.
Both antennas were at about 36 ft up at the base.

According to a modeling exercise I did once, the best way to
run a 5/8 GP is with 5/8 radials. I've also used 3/4 wave radials,
which seemed to work well. But according to the modeling, the 5/8
radials will give more gain. Starts to resemble a dual 5/8 collinear.
And naturally, you would want to use a decoupling section for the
best performance.
This is pretty old, but compares the different lengths for 10m
use.
http://home.comcast.net/~nm5k/acompari.htm