[Antennas] Ground System for 20 mtr Vertical?

Sun Apr 25 17:40:46 EDT 2010

I'm working on a new portable/QRP 20 meter antenna to go with my K1. 
Today I use a 67' endfed wire. It works pretty good but I need something 
that does not require a tree/support. I'm settling on a vertical built 
around a 16.5" crappie pole on top of a 4' piece of PVC pipe. I'd guy 
the 4' PVC pipe with my radials.
Mar 2010 QST has a good article by N6LF documenting his experiments with 
ground systems. Based on his experiments 4 elevated radials only 4' off 
the ground should work as well as 64 radials laying on the ground...good 
thing, I'm not going out and laying 64 radials around a picnic table for 
the afternoon...but what length? He found that shortened radials (21' on 
40 meters) work 3db better than 32' radials. He attributes this to the 
maximum radial current point needing to be at the antenna base, 
something that does not happen on quarter wave long elevated radials.
Question....How can I easily measure radial RF current to identify the 
right length that places the current near the antenna base for my 
antenna? Can I just use very low power and a field strength meter, 
running it along the radial to ID the peak point? If not this, what?
tnx es 73,
Niel - W0VLZ
http://www.prismnet.com/~nielw/wa5vlz.htm