[TowerTalk] No of Ground Radials
hasan schiers
schiers at netins.net
Wed Aug 9 11:58:32 EDT 2006
Phil,
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
Example:
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".
73,
...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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