ZL2HAM Wrote:
-----Original Message-----
>> From: Rick Kiessig <kiessig@gmail.com>
To: Jwpjj@aol.com; topband@contesting.com
Sent: Tue, 4 Nov 2008 2:06 am
Subject: Re: Topband: Inverted L
John,
4 radials isn't anywhere near enough (unless they're elevated). SWR
doesn't
tell you anything about antenna efficiency. Ideally, you want to keep
adding radials until your feedpoint impedance levels off. A good
antenna
analyzer (like the AIM 4170B) can be a big help.
The easiest way I've found to optimize your radials is to walk around
the
area where your antenna is, and place a small marker every 0.015
wavelengths
(2.5 meters for an antenna on 160), up to about 0.25 wavelengths away
from
the antenna. Then run radials to those markers, so that the tips are
0.015
wavelengths apart. Space the radials out evenly if you would rather do
the
work a little at a time. If you're limited by the amount of wire you
have,
make the radials shorter, but keep the tip spacing at 0.015 wavelengths.
As you add radials, ground resistance will go down, antenna efficiency
will
go up, and SWR will probably also go up. Use an L-network (or
variations)
or a tuner to match the antenna to your amp/rig.
73, Rick ZL2HAM
W2PM Responds:
I have 32 mostly 1/4 wave radials laid out about 200 degrees around the
base - I cannot get to the other side to complete the circle because of
property boundaries and grouchy neighbors. Laying these out in a neat
radial field made a huge difference here. Before I took the time to
lay these properly, I had all sorts of wires running random. Some were
short, many 1/4 and perhaps about 22. The 10 additional radials I
added when I redid the field were mostly short, 1/8, but the
performance of the antenna went up considerably. And on 80, (I have a
trap at 65 ft on the vert section) I break any pileup Ive heard on 75
phone first or second call. And on poor nights I am often the only
station DX hears. With the old messy radials I was no where near as
competitve.
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