Hi Jim,
The one thought that occurred to me — given the K7LXC need to avoid horizontal
wires — was in remembering K9YC's work at using a choke to make a vertical
dipole by putting the choke 1/4-wl away from the end of the coax (at which
point the centre conductor is connected to the skyward half of the dipole).
What I wondered about, given the 143 feet of height for a full-size (with
AB7E's 10 feet of elevation), is whether it would be possible to load the
shield so it, and perhaps the upper portion, could be physically shorter, such
as running a conductor connected to the shield at the choke back along the coax
like a linear-loading conductor (maybe not necessarily snug against the coax,
of course).
Could one break the shield at some advantageous point to insert a coil?
(Without breaking the centre conductor, of course.)
Just spit-ballin' here.
73, kelly, ve4xt
----- Original Message -----
From: "jimlux" <jimlux@earthlink.net>
To: towertalk@contesting.com
Sent: Tuesday, October 20, 2020 3:21:30 PM
Subject: Re: [TowerTalk] Vertical dipole other choices?
On 10/20/20 1:01 PM, David Gilbert wrote:
>
> Electrically, a half wave vertical dipole is not a lot different than a
> quarter wave vertical fed against radials or a counterpoise, but it
> requires a LOT more height to put it up. I just modeled two different
> antennas in EZNEC+ as a comparison (both over medium ground):
A lot of these antennas are an electrically short dipole. so they don't
require the height. From a gain standpoint, an infinitesimally small
dipole is 1.5 dBi and a full size dipole is 2.5 dBi (mostly from the
broader lobe for the short antenna).
What might be interesting is modeling, say, a 25 foot dipole with the
center 13-14 feet off the ground.
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