Topband: Tuning elevated radials

[K9AY]

> I'm working on building an elevated radial vertical.  After installing the 
> radials, I have a question about what I'm finding.
....
>
> There are three elevated radials, each about 1/4wL and each about 120 
> degrees apart.  At resonance, I find that the current was not well 
> balanced between the radials.  So I started trimming.  It turns out that 
> by trimming the highest current radial, the system came into relative 
> balance.
>
> Ford-N0FP
___________________

Ford,

You hit one of my "hot buttons" -- I have not seen any convincing evidence 
that equalizing currents in elevated radials is a valid exercise.  Even if 
it is, the "solution" of changing radial lengths has much greater potential 
for introducing pattern skew.

What is more important is to make sure that each radial is actually an 
electrical 1/4-wave, with maximum current at the common connection.  The 
easiest way to to this is to grid-dip or measure the impedance of pairs of 
radials as dipoles, adjusting the lengths until the dip is at the desired 
frequency and/or reactance is zero.  (Actually, you just want them of equal 
electrical length so they have similar current distribution -- this is by 
far the easiest to accomplish when they are 1/4-wavelength.)

Layout symmetry is also important for omnidirectional radiation (if that's 
what you want).  Belrose has written quite a bit on this topic.

Of course, as you add more elevated radials, the need for any of this is 
reduced, since the return currents will be spread out, minimizing the effect 
of any individual radial.

73, Gary
K9AY