[TowerTalk] 4-square over existing groundscreen

[Tom McAlee]

Peter,

>From my experiences, I won't work nearly as well as having the radials 
extending out from the 40m verticals themselves.

Others here can probably offer a better technical explanation as to why, but 
I'd say its because with 1/4-wave verticals the electric field near the 
antenna is very low; the current the radials are trying to pick up are the 
currents that induced by the magnetic field and those currents are 
tangential to the magnetic field (and therefore run radially outward from 
the vertical, being strongest at the center).

I don't know if thats a full technical explanation, but in experience I 
noticed a big difference.  I had a 40/80 meter vertical with many radials 
(150, 1/2-wave on 80m).  I put up a 40m 4 square around it.  Later, I took 
down the vertical and re-did the radial system to have 480 4/10-wave radials 
under each 40m vertical.

I was able to compare the 4 square with the original radial system and with 
the new radial system against a 3rd antenna (a wire delta loop) and A/B 
tests showed significant improvement.

And, with the single radial system the feedpoint impedance was pretty high. 
I don't recall the exact number, but it wasn't nearly as low as the 36 ohms 
I got with the radials under each vertical.  That tells me the ground losses 
were a lot higher.

73,
Tom, NI1N

----- Original Message ----- 
From: "Peter Voelpel" <peter.voelpel at t-online.de>
To: <towertalk at contesting.com>
Sent: Monday, May 16, 2005 9:31 AM
Subject: [TowerTalk] 4-square over existing groundscreen


>I am thinking of erecting a 4-square for 40m around
> my 80m vertical which uses 130 buried radials 15-20m long.
> Will that work if I connect the 40m verticals to the existing radial
> system?
> The other idea is to have 2-4 elevated radials on each radiator and
> benefit from the 80m groundscreen
>
> 73
> Peter, DF3KV
>