ON4UN's series of books have always had way too many individual assumptions
and we all know what happens then.
Those books offer a place to start and then apply your own unique soil and
local conditions and change as needed.
Carl
KM1H
----- Original Message -----
From: "Buck wh7dx" <wh7dx@hawaii.rr.com>
To: <topband@contesting.com>
Sent: Wednesday, March 06, 2013 3:42 PM
Subject: Re: Topband: Elevated Radials EPILOGUE
There is some good stuff in ON4UN Low Band Book - Chapter 9-10 on
Elevated Radials.
He suggests that an elevated system would be even better above ground
versus on the ground in poor conditions. References 0.1 wave height or
less. For 160m that could be 50 feet down. In Section 2.2.7 K3LC says
that there is no point in raising radials any higher than 6 meters on 160
or 3 meters on 80 meters. Such a height would be between 0.2db of what
can be achieved with 64 buried radials... N7CL says they need to be
higher....
The perfect on ground system might be 50-100 1/4 wave ground radials...
In 2.1.2 he warns of trusting modeling because of outside factors.
9-12 Figure 9-18 (modeling) regarding 160m gain using 1/4 wave is
interesting over average ground. If you wanted max. it suggests using
120 - 80meter radials. But the difference between 120 (1.5 dbi gain) and
going with 32 (1.0 dbi gain) would make one wonder if it was really worth
it for another 1-2 miles of wire.. work? 0.5 dbi gain?
The Conclusion in 9-14 is interesting.. basically saying..
"Take the example of an 80-meter vertical over average ground: going from
a lousy eight 20-meter long radials to 120 radials would only buy you
1.4db of gain, which is less than what I think it is in reality. In very
good ground that difference wold be only 0.7 db!"
2.1.3.2 - "From these almost 70-year old studies, we can conclude that 60
quarter-wave long radials is a cost effective optimal solution for amateur
purposes.
K3NA's work in 2.3.1.3 talks about using 1/16 wave radials.. not going
beyond 48.. but that doesn't match up with N6BV's work several years
prior.
In 2.2 Elevated Radial and beyond it's gets really interesting and less
conclusive?
The Conclusion States - "If you want to play it extra safe, and if you
have the tower height, get the radials up as high as possible and add a
few more. Use a ground screen if you have it.
"It all is very logical. Get away from the lossy ground or hide the lossy
ground with a dense screen using many radials. No free lunch!".....
This was one book and it goes on.....
All of this sounds like a great episode for Ham Radio Myth Busters.......
73,
Bryan
WH7DX
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