[TowerTalk] Vertical dipole other choices?

[ve4xt at mymts.net]

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 at earthlink.net>
To: towertalk at 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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