[TowerTalk] Vertical Base Insulators

[Daly, Greg TQO]

Dan:

     For the truly frugal way out, I've used a Coke bottle stuck in the
bottom of my 50 foot Rohn push up mast, and a 12 inch square cinder block to
keep it from sinking into the mud (I'm in Oregon, do you guys know about mud
in California?)  I've also used old telephone line insulators, McLaughlin
#19 are very common and the insulator collectors let them go for cheap if
they aren't a nice color.... They have a nice domed top for the mast to rest
on, with a 3 inch skirt to keep the insulator from getting shoved up into
the mast, and they are a nice sized chunk of glass.... If it shatters the
mast is only going to drop a few inches, and replacements are cheap.... I
don't know the breakdown voltage from the skirt of the insulator to ground,
but it's got to be several KV. If you're worried about the base sliding
around, telephone line insulators are threaded to screw onto a peg on the
cross arm on the pole, you could have it rest on something similar

73 Greg WB7RSG

-----Original Message-----
From: Dan Levin [mailto:djl at andlev.com] 
Sent: Friday, July 02, 2004 9:08 AM
To: towertalk at contesting.com
Subject: [TowerTalk] Vertical Base Insulators


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?  How far from ground does the bottom of the mast have
to be?  What materials are best to use as the insulator?  What materials
should I avoid?

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.

 

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".

 

Thanks!

 

                                    ***dan, K6IF

 

Don't forget the California QSO Party, coming up the first weekend of
October!

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