Believe me, I am no expert at this, but I will pass on some stuff I was
playing with and thinking about.
I have been doing a bunch of modeling of a 114' tower with 127 to 132'
active top guy wires for 160. My current inclination is to use switchable
guy choice then connect the remaining two to the shield on the coax thru a
20 uH physically large tapped inductor. This lets them work as a reflector.
With the Yagi's on top, you get a 25-30 degree take off angle, about 3 dBd
and a 120 degree pattern. The pattern looks like a lopsided donut laying
flat on the table with the larger part of the donut in the direction of the
chosen guy wire. Front to back isn't much, about 6 dBd, but the near
vertical stuff (i.e. those stations just beyond ground wave range) are
significantly attenuated. By changing the inductor and adding another
tapped inductor to the driven element, it also plays on 80 and 40. On 40
you are running it in a multiple wavelength mode and the results get rather
impressive.
Biggest problem is lots of relays and inductors clear up at the top of the
tower in a metal box (preferably water proof). This adds wires and wind
load.
Computer modeling beats the heck out of cut and try.
One thing to note that you are using guy wire for the element, so your
ohmic losses will be higher.
Hope this gives you a starting point.
de n0yvy steve
______________________________ Reply Separator
_________________________________
Subject: Crank-Up Guys
Author: Paul Mackanos <k2db@FRONTIERNET.NET> at ccmgw1
To: <towertalk@contesting.com>
Date: 8/19/96 6:19 PM
Hi guys & gals, at a recent weekend gathering of a few fellow hams, the
following discussion evolved:
How about using 3 full sized 40 meter slopers as a guying system on a 51'
Tri-EX Crank-up. The idea
was to have a remotely controlled antenna switch mounted on the tower.
In looking an the 95 ARRL Handbook, and finding Antenna Wire Strength in
Table 30.33, some interesting
discussions followed. Assuming that using insulators, supports, etc, at
least as strong as the wire,
can it be done, has anyone done anything like this ??
Thanks for the replies, in advance !!!!!
|