On Jun 15, 6:46 pm, Tom Ring wrote:


5/8ths isn't what it's advertised it to be. I'd explain it, but I have
to finish watching SG1 and then F1 practice session 2.

It has to do with "ground planes" and the fact that they are mostly
fictional in this case. And that the second 5/8ths doesn't have the
needed "ground plane".

I'm sure someone else will explain fully.

tom
K0TAR

In my opinion, a 5/8 vertical should be set up to be a complete
antenna, which means it needs 5/8 on the "other" side..
Running a 5/8 over 1/4 wave radials is fairly perverted.. It's no
wonder it doesn't live up to expectations.
But a dual 5/8 collinear is a pretty stout vertical, as far as
verticals go. I think 5/8 ground planes should use either
3/4 or 5/8 wave radials if one uses actual radials, to
more closely simulate a collinear.
A dual 5/8 collinear is a complete antenna, and requires
no radials at all.
I compared all the usual types "lengths" on 10m a few years
ago, and my 5/8 GP with four 3/4 wave radials handily beat
a base fed half wave, with and without decoupling. I used
3/4 wl radials because I wanted a low Z.. But if I made one
with real steeply sloped radials, I think I would make them
5/8 wave.
But, I never got around to trying one with 5/8 radials, so
not sure how it would compare to my last version.
BTW, all my tests were done using "ground/space" wave
locally, and were pretty accurate as far as telling which
was best. I'm using a low angle path for that type of thing
too.. Many of the people I talked to were 20-30-40 miles
away.
MK