Understand. However in this case we are not trying
to confirm loobes in the vertical plane. We are trying
to improve the near field to get less R-loss, that we
can confirm and measure without using helicopters.
Lets stick to the original issue.
73 Jim SM2EKM
-----------------------------------------------
Jim Lux wrote:
At 05:09 PM 12/18/2003 +0100, Jan Erik Holm wrote:
You need no helicopter. In practical sense just
measure the ground wave.
We are not trying to confirm loobes in the vertcal
plane, then you need helicopters.
73 Jim SM2EKM
But, for HF skywave communications, you ARE very concerned about the
skywave. The near and midfield (say, out to 10-20 wavelengths) will
have a huge effect on what the pattern looks like close to the ground,
or, at least up to 20-30 degrees, which is usually what folks are
worried about.
It would be very, very difficult to relate, with any confidence, the
measurements you might make at ground level to the gain at 5,10, or 20
degrees above the horizon. (unless you're like Rick Karlquist, with an
antenna out Galt,CA in the middle of a flatter than Kansas plain with
fairly uniform soil characteristics for miles in every direction)
A very small change in the soil characteristics radically changes the
depth of the "null" at the horizon for horizontally polarized antennas
over ground. Less of an effect for the vertically polarized antennas.
Since almost all practical antenna systems radiate both polarizations,
and the skywave itself is fairly randomly polarized, such things are
important.
---------------------
Jim Lux wrote:
Hard to do, in a practical sense... You'd need a measurement receiver
in an
airplane, helicopter, balloon etc, because the field strength at "ground
level" isn't really what you're interested.
Perhaps measuring beacons before and after? But you've got the
propagation
variations to worry about.
This is why evaluating HF antennas is such a royal pain.
----- Original Message -----
From: "Jan Erik Holm" <sm2ekm@telia.com>
To: <towertalk@contesting.com>
Sent: Wednesday, December 17, 2003 8:37 PM
Subject: [TowerTalk] Re: One more ground radial question
Is something like this ever confirmed by field
strenght measurements?
73 Jim SM2EKM
--------------------------------------------------
Don Havlicek wrote:
Yes!
In my case ... 60 radials spaced 6 degrees apart .. then
concentrations
of ten radials at 1 degree each for Europe, Japan, South America, and
VK/ZL ... works like gangbusters .. all I need now is to clean out the
shack and put a new feedline out to the vertical again!
Don
N8DE
va3pl@cuic.ca wrote:
----- Original Message ----- From: "Don Havlicek" <n8de@thepoint.net>
To: <kb9cry@comcast.net>
Cc: <TowerTalk@contesting.com>
Sent: Wednesday, December 17, 2003 12:12 PM
Subject: Re: [TowerTalk] One more ground radial question
I believe the word "optimum" should be replaced with "sufficient".
My experience with verticals tells me that 100 radials works much
better than 60, especially when concentrated in certain directions.
,
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Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
any questions and ask for Sherman, W2FLA.
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