Topband: Radial requirements for 1/2 wave vertical?

[Richard (Rick) Karlquist]

Mike Waters W0BTU wrote:
>> From: dick-bingham <dick-bingham at hughes.net>
>> Subject: Re: 100 Watts
>> To: "Mike Waters W0BTU" <mrscience65704 at yahoo.com>
>> Date: Thursday, February 18, 2010, 8:34 PM
>> Nope !!  A half-wave 
>> end-fed antenna feedpoint is a very high impedance 
>> (it's an open circuit at both ends and therefore virtually
>> a zero-current point) which is easily fed using a parallel-L-C network.
> 
> I mostly agree. Years ago, I had a half-wave vertical for 20 meters,

  with 4 elevated radials, and that's how I fed it. I used to work VK's 
and ZL's nightly with it from my old QTH in NW Ohio.
> 
> [snip] 
> 
> It's true that the  radial current _at the feedpoint_ is lower than

  a 1/4 wave (or shorter) vertical. But I think I read in ON4UN's book

  "Low Band DXing", that the radial requirements for a half-wave vertical

  were substantial. That is, you need a better radial system for a 1/2 wave

  vertical than you do for a 1/4 wave (or shorter) vertical
>
> 73,
> Mike Waters
> W0BTU

This often repeated idea about half wave verticals needing many radials
has a grain (a very small grain) of truth in it.  If you want to get
the theoretical 2 dB of gain that a half wave vertical has vs
a quarter wave vertical, you may indeed need a big ground screen.

But in actual tests, I have found that a half wave vertical with
essentially zero radials is as good as a quarter wave vertical
with a bunch of radials.  See:  http://www.n6rk.com/ground.pdf

I have been using 1/2 wave verticals w/o radials for years in
many locations and they have always worked fine for me despite
their seeming "impossibility".

Rick N6RK