Topband: Vertical antenna components available

[Donald Chester]

In case anyone is interested in constructing a series fed vertical antenna 
using a Rohn 25 tower as radiator, I came across a source of components at a 
hamfest this morning, at very reasonable prices.

Two AM broadcast tower base insulators, specifically designed to fit the 
Rohn 25 are available. (He had three, but I purchased one to keep as a spare 
for my own 25G tower).  The insulators are real glazed porcelaine, 4" in 
diameter,  7" tall, with cast steel end bells and base plates, all of which 
are hot-dip galvanised.  They are designed to bolt directly onto the Rohn 
25TG tapered base section.  An adaptor plate could be constructed for use 
with a conventional 25G section.

There is one Rohn 25TG tower section sitll available.  If not purchased 
soon, a local ham may use it on his tower by burying the bottom of the base 
section in concrete, conventional ham radio style.  There were originally 
three others, but they have already been sold, and may have met similar 
fate.  The 25TG consists of a normal 25G section but the bottom couple of 
feet of the tower legs are bent inwards to a taper, like the point on a 
pencil, and welded onto a 5/8" thick round steel plate approximately 10" in 
diameter.  The plate has 3 holes for bolting onto the base insulator.  The 
tapered part of the tower  legs is reinforced with solid steel sheet metal 
instead of the normal zig-zag steel rods.  One of the insulators described 
above was used with this tower section.

There are about 60 rigid fibreglas insulators designed to attach the guy 
wires to the tower, with  a 10,000 lbs breaking-strength rating stamped on 
each.  This provides a long insulative path between the metallic guy wire 
and the vertical radiator.  They are designed to also serve as torque arms 
for the guy wires, to reduce the possiblity that the tower might rotate 
during a severe storm.

There are "hundreds" of #502 "johhnyball" strain insulators taken from the 
the guy wires.  The vendor said they were attached using u-bolt cable 
clamps, and that the guy wires were hurriedly cut apart using a bolt-cuttor, 
with the wire-ends and clamps still attached to many of the insulators.

An AM broadcast station used this material in a four-tower directional 
array, but discontinued their nighttime directional service because it was a 
money loser, so they gave the towers and hardware to the local ham club in 
exchange for taking them down.  The array was originally built iabout 1980, 
so the stuff is relatively new as used disassembled tower material usually 
goes.  Members of the club divided up the 25G tower sections, but had no use 
for the insulator hardware, and no-one seems interested in using the 
remaining 25TG section to build a base insulated tower.

The material is located in Murray, KY.  Contact Bill Call, KJ4W.  His phone 
# is (270) 753-7870.  His e-mail address is:  kj4w at arrl.net

I would like for interested topbanders to get this material and construct 
some new no-compromise series-fed vertical antannas.

Don K4KYV

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