[TowerTalk] No of Ground Radials

hasan schiers schiers at netins.net
Wed Aug 9 11:58:32 EDT 2006


60 1/4 wave radials is OVERKILL in many situations (all but the worst local 
ground characteristics), and a LOT more work and expense than is needed. 
than is needed. See the K3LR radial optimization study. It shows what is 
required for a specified loss of 0.5 dB ...or how to make the best use of a 
fixed amount of wire.

The formula goes like this:

N = ((2*PI*W)^0.5)/1.2

N equals the square root of the quantity (2*PI*WireLength) divided by 1.2

Where N = number of radials

Where W = length in meters of available wire to make the radials

Length of radials = W/N

and the constant 1.2 is the tip separation in meters to produce the proper 
density on 80m ..this would be twice the density one needs for 160m and half 
what is needed on 40m. The value for minimum tip separation is simply .015 
wavelength. So if you calculate wavelength for the freq in use, multiply it 
by .015 and that gives you the value for tip separation in the formula 
above. For 80m it is 1.2 meters


You have 500 meters (about 1640 feet) of radial wire available for your 80m 
vertical. How many and how long should the radials be:

46 radials, 10.8 meters (35.6 feet) will produce the lowest possible loss 
for this amount of available wire.

There it is, a simple formula for how many radials to put down if you have 
"only so much wire". These days with copper prices through the roof, it pays 
to be economical and still stay within 0.5 to 1 dB of  "what's best".


...hasan, N0AN
----- Original Message ----- 
From: "Phil Camera" <kb9cry at comcast.net>
To: <TowerTalk at contesting.com>
Sent: Wednesday, August 09, 2006 9:37 AM
Subject: [TowerTalk] No of Ground Radials

> Someone/body did some testing in this regard and from what I remember the 
> general rule of thumb is 60  1/4 WL radials are best.
> Phil  KB9CRY
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