Ive used this antenna at K3LR. It works very, very well! Dont change anything
and you will be very happy :)
Best regards,
Scott W3TX
On Aug 3, 2014, at 5:09 PM, "L L bahr " <pulsarxp@embarqmail.com> wrote:
Most of the radiation comes from the current part of the antenna which is going
to be close to the center point of the driven element. If you are using a U
shaped channel 2 foot long at this area of the antenna, you will be pumping RF
into the channel at the high radiation point of the antenna for 2 feet!
Looking at a whip antenna on a car, if you place the whip low on the rear
bumper and have a lot of it length within near proximity of the auto body, it
will in no way work as good as if the base of the antenna was "in the clear"
say at the top of the trunk. A lot of the radiation is going to go right into
the car body. I'm not so concerned about the capacitive coupling. Maybe this
is part of the reason the center is 50 ohms. I'm concerned about the RF being
shorted and grounded thus reducing radiation efficiency with this long 2 foot
piece of aluminum channel.
Lee, w0vt
----- Original Message -----
From: "David Gilbert" <xdavid@cis-broadband.com>
To: towertalk@contesting.com
Sent: Sunday, August 3, 2014 3:42:26 PM
Subject: Re: [TowerTalk] Building a W6NL Moxon 40 Meter Beam.
1. There is nothing inherently wrong with "coupling to ground" at the
feedpoint. As long as whatever capacitance that may be there (which I'm
not convinced would be significant anyway) is relatively low loss it
would just be part of the overall tuning system. Besides, coupling to
anything is not uniform along an antenna. The net effect of capacitive
coupling is going to vary as a function of the voltage at that point,
and the voltage at the center of a "dipole" is low while the current
there is high. That's why loading coils (which require current to be
useful) are placed more toward the center of a typical halfwave element
(see note below) and capacitance hats (which require voltage to be
useful) are placed near the ends.
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