Brad Rehm wrote:
>
> > I was surprised to find that adding three guy sections, each 15-20
> > feet long, had no measurable affect on the resonant frequency of the
> > tower.
>
>
> Brad,
To create a more effective top hat out of tower top guys, that slant down
at no more than 45 degrees, is to connect jumpers around connecting the
tower side of each insulator to each other. (A length of a least 20 to 25
percent of the tower height is what I used.) This method should mitigate
some of the shortening effect of the slanting 3 guy capacity hat.
Additionally there will be greater parallel capacity to the ground below.
This should elevate the current portion higher on the tower, raise the
feed point impedance, and improve the efficiency. I remember working with
broadcast consulting engineer John Mullaney (Multronics) during the 60's
using this approach for a three tower directional array in Minneapolis.
Connecting the top guys around the perimeter of their insulators, I
recall, made all the difference in the world for driving up the base
impedance. The FCC granted a CP based on Mullaney's design. I believe the
system is still in operation at KQRS.
Herb Schoenbohm (ex-KV4FZ)
>
>
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