[TowerTalk] Vertical Base Insulators

[n8de at thepoint.net]

Dan,
My comments are inserted below:

> I'm planning to install a Channel Master  pushup mast (with stinger on
> top)
> as a vertical antenna for 160 meters.  The mast is steel, and about 2.5"
> in
> diameter at the base.  It will be guyed.  I have two questions:
>
>
>
> 1)       What is the conventional wisdom about insulating the base of such
> a
> vertical from ground?

This works OK, provided mechanical strength is sufficient.

> How far from ground does the bottom of the mast
> have
> to be?

Low voltage point in most respects, so a large 'gap' is not required.

> What materials are best to use as the insulator?

Any material which will not breakdown under usual conditions of moisture,
dirt, UV, and RF.  Included among these are:  fiberglass, Delrin, Teflon,
and other synthetics.

> What materials should I avoid?

I'd avoid anything containing carbon fibers, including BLACK-colored
pieces of the above-mentioned insulators.

>
> 2)       Does anyone have a specific proposal for a base insulator for
> such
> an antenna?  I'm especially interested in anyone who is using such a mast
> as
> a vertical, and has real experience with the mechanical and electrical
> issues of all of this.

I used fiberglas ROD to insulate my 64' vertical TOWER for use on 80m. 
It's been up and used in this manner since 1988 with NO problems.
>
>
>
> My current plan is to use a 1" piece of Delrin with a thin steel plate on
> top of it (to spread the weight/pressure) as the base insulator.  What I
> don't know is whether one inch is far enough from "ground".

Not sure if I'd use a FLAT surface, as this would collect moisture, dirt,
etc ... one inch is sufficient for spacing, due to the low RF-voltage
present at that point.

>
>
>
> Thanks!
>
>
>
>                                     ***dan, K6IF

Good luck!
Don
N8DE



>
>
>
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