Hi everyone,
First, my thanks for all of the responses - what great ideas! So, my
vertical mast project now has several great insulator options.
Now, back to the other project - finding a way to string two parallel wires
between two masts for a halfsquare array. I know this isn't very
interesting to those who have trees and towers, but these two masts are
going to be my wire antenna experiment workhorses for a couple of years and
the thought of getting more than just a single skywire out of only two masts
really has me excited.
My first thought about finding lightweight, rigid materials to 'spread' the
two wires got very little reaction (because it just won't work). So, how
about this:
A collar about 6 to 12 inches long with fits over the top of the mast. The
collar will support two struts about 21 feet long. The struts go up at
about a 45 degree angle from opposite sides of the collar. The distance
between the outer ends of these two supports is about 36 feet. Extra
strength can easily be provided by running rope between them at several
points. The wind loading on such long struts each supporting wires will
probably put quite a bit of torque on the collar, so I could attach one or
even two tiers of guys to the collar.
This affair would look like the upper half of a quad spider and would raise
the wires about 12 feet higher than the top of the mast (a dizzy 73 feet
from a 61 foot steel telescoping mast).
Now, there are a lot of guys out there with tons of experience with things
up in the thin air - I wonder if this affair can be made strong enough
without adding so much weight that my two Swartzenagers can't push the mast
up? Tubing? Aluminum angle? Fiberglass?
I know from my meager two months experience with a wire antenna between to
masts that it takes a lot of pull (about 30 pounds) to take the slack out of
the wire (a heavy G5RV) - so this force is going to be felt at the tips of
the struts, and even if they are held tightly together with ropes at several
points, that's a lot of pull (downward and in the direction of the wire).
Of course, the halfsquares won't be nearly as hard to raise without the
ladder line and balun pulling down.
I hope this is (almost) as interesting to some of you as it is to me.
BTW, a solution here could help a lot of guys without trees put up wire
arrays with only a couple of masts (are there a 'lot' of guys like that?)
SIDE VIEW (behind the mast - looking toward the other mast)
p.....................p<----pulleys (36ft apart)
. .
. .
...............<--------support ropes between struts
. .
. .<----------'struts' (about 21ft long)
. ||| .
. ||| .
.|||.
|||<-----collar
|||
|||
|
|<------mast
|
//
73s
Frank T. Brady - W0ECS
Wildomar CA
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