-----Original Message-----
From: w8ji.tom [mailto:w8ji.tom@MCIONE.com]
Sent: Tuesday, December 22, 1998 6:42 AM
To: N2TK
Subject: Re: [TowerTalk] FW: Help - 80m 4 square
Hi Tony,
> Performance - about 10-18 db f/b and very slight gain over a Cushcraft
AV80
> 36' vertical with 4 elevated 1/4 wave radials.
I'd bet money your Cushcraft vertical, using only four radials, is several
dB weaker than it could be with a good ground system.
It is not surprising the 4 square only has about the same performance when
compared to it, since the 4 square only has one radial per radiator.
No matter what you read in amateur texts, your antennas need a better
ground system. You'll never find a single actual FS measurement to support
any of these "one or four radials are enough" theories.
> My questions on trying to improve performance
> - Thought performance would improve by making the verticals more
vertical. I
> can do that by making them
> "T's". The vertical portion would be about 45-48' before I added the T.
If the antenna already has good F/B, the antenna does not have a radiator
problem. It has an efficiency problem. Sloping the wires hurts F/B long
before reducing forward gain.
> - With the radials, do you think I would get a measurable improvement by
> either adding one or two more per leg?
Anything would help, especially up to about 30 radials per element.
> What about the articles on 1/8 wave
> radials? Would that work with a coil?
While well written, virtually all elevated radial articles completely lack
any directly measured FS data. Equal current in each radial does not
necessarily guarantee lowest loss or best performance, neither does a low
feedpoint resistance.
One test of these articles is to read carefully and see if the author
suggests a feedline decoupling choke, and warns the user to keep the
counterpoise totally isolated from earth grounds even through the feedline.
Just by strapping the counterpoise common point to three six foot ground
rods, FS dropped over one dB. Ten feet of coax in a choke balun could
improve a system a dB or more, yet no one mentions that when they claim
"equal performance" to a full size conventional system.
I installed elevated systems here, prior to installing my verticals, and
measured FS. The 1/8 wl long radials were the poorest system in
performance, about equal to a two elevated radial system with full size
resonant radials. Both were 6 to 10 dB down from a conventional ground
system with 60 1/4 wl radials.
Believe me, if I could have used a few thousand feet of radials instead of
50,000 feet and had near optimum performance I would have.
> - Is performance suffering by cutting the verticals and 1/4 wave matching
> lines for 3.65 and then switching in a coil in the radials for phone and
cw?
Backwards Tony, cut it for phone and switch in the coils for CW.
73 Tom
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