On 25 feb, 09:10, wrote:
On Feb 24, 2:44*pm, Ken Slimmer wrote:

Wim;
* * *Thanks for your input, I just noticed that I had my finger on the
shift key when I posted the subject, so it came out as @0 meter.. *:-)
* * *I don't ever plan on running high power, 100 watts is about my
limit. *I do want to stick to putting a vertical up. *I have an old 1/4
wave 40 meter vertical that I was going to scrounge parts from. *

If you already have a 32 ft radiator, I would go with the half wave.
Feeding one is simple. I prefer the "gamma loop" type of feed.
I've built many of those, and they are simple to get going, and work
well.
The antenna as it is does not require radials to function as a
"complete" antenna. Most will work fine as is, with no radials.
But if one wants to further improve one, they can be further decoupled
from the feedline using decoupling sections.
The way I usually decouple a base fed half wave is to use a 1/4 wave
length of coax dropping down the supporting mast to a union which
I clamp a set of quarter wave radials. The shield of the coax is
bonded
to the radial set.
That will do a pretty good job of decoupling the feed line, if common
mode current ends up a problem.
But like I say, I've never had any problems using one with no radials.
I consider the decoupling as optional.
A 5/8 wave GP would be nice, but that will take a pretty tall radiator
on 20m, and may be unpractical.
Also, I don't use 1/4 wave radials under 5/8 verticals.
This page explains my position on that issue..http://home.comcast.net/~nm5k/acompari.htm
If you want to avoid the funky high angle lobe you often
see on poorly designed 5/8 wl antennas, use 5/8, or 3/4
wave radials.
I've done very extensive testing of all the usual types of verticals
on 10m, and the 5/8 GP is the best performer of the bunch,
even with it's supposed warts.
Even the 1/2 waves I used with decoupling sections were never
as good as the 5/8 GP when working far off space wave stations.
But like I say, a 5/8 GP on 20m could end up being a real pain
to deal with. You are talking a 41 ft radiator, and that needs a
supporting mast under it. Radials under it too.
BTW, a 1/4 wl GP is not a bad antenna if you want to take the
easy way out. Needs radials though.
I haven't looked at the collinear design, but sounds like more
trouble than it's worth. Would be tall too.
Most higher gain collinear antennas used on 20m would
probably be horizontal wire affairs.

Nice simulations, and nice results also!

Best regards,

Wim
PA3DJS
www.tetech.nl
the mail is ok when you remove abc.