December 1962 Popular Electronics
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As with just about every other type of hobby anymore, creativity
and mechanical aptitude is not much of a necessity if you have
money to spend. Heck with all the government handouts these
days, all you need is other people's money. There is such a
plethora of options available for every conceivable need to
satisfy whatever degree of complexity you want your hobby to
entail. The back 1/3 of every edition of the ARRL's
magazine is loaded with advertisements offering antennas, radios,
towers, test equipment, guy wires, insulators, cables, connectors,
soldering stations, semiconductors, tubes, nuts and bolts. It
is a wonderful world we live in if your desire is to engage
in the operational aspect of a hobby rather than the building
and experimenting aspects. It was not always so. Half a century
ago the average hobbyist needed to scrounge for components that
could be 'repurposed' for use as needed. Sure, there were many
sources for common components then, but even if they were available,
hobbyists either could not afford them or they had a desire
to experience the pride that went along with being a craftsman
as well as being an operator. This article from 1962 is a prime
example of repurposing available parts for achieving a goal.
Base-Insulating Your Vertical
By Howard S. Pyle, W7OE
Thousands of Hams find the insulated-base vertical radiator
an ideal solution to their antenna problems. But, while the
radiating element can be made of water pipe, electrical conduit,
aluminum tubing, "rain-gutter" pipe, or even aluminum irrigation
piping, the choice of material for the base and base-insulator
is often not quite so obvious.
Before we illustrate how easy it is to design an effective
base-insulating system, a few things about the construction
of vertical antennas need to be reviewed. First of all, the
most popular height for a vertical is in the neighborhood of
33 feet. This makes a half-wave antenna for the 20-meter band,
a quarter-wave for 40 meters, and an eighth-wave (or, with suitable
loading, a quarter-wave) antenna for 75 - 80 meters.
Photos point out details of W7OE's unusual
Any vertical piece of tubing 33 feet long, of course, must
be guyed. And, while it's not within the realm of this article
to discuss guying methods, it should be mentioned that guy wires
must be broken up into short electrical lengths by means of
insulators (the small "goose-egg" or "airplane" type is most
commonly used). Generally, each guy has one insulator near the
radiator, one in the center, and one at bottom.
The point we'd like to make here, though, is that the necessity
for guy wires is actually an asset when it comes to picking
out a base-insulating system. Most of the horizontal stresses
caused by the weight of the radiator and the winds are taken
up by the wires, the insulator merely acting as a vertical support.
This being the case, the insulator need not have great mechanical
strength and need not be firmly anchored to the foundation on
which it stands.
Constructing the Base. The first thing you need for your
base-insulating system, naturally, is a base. As illustrated
in Figs. 1 and 2, this can be a very simple structure - but
it should be made of cedar, or some similar weather-resistant
wood. And for further protection from the weather, the base
should have two coats of outside paint or varnish.
Fig. 1. - If you don't mind nails in your
roof, this simple base will do for almost any vertical antenna.
It requires few materials and can be built quickly.
If you can toe-nail your base into the roof or into some
other rigid surface, the design of Fig. 1 is a good one. It's
nothing more than a 10" square of 1" x 10" stock supported on
two 2 x 4's. Use 8-penny nails both to put the base together
and to fasten it to the roof. A hole for the insulator, if necessary,
is made in the center of the square.
Should you have reservations about nailing into the roof,
you'll probably be more interested in the base illustrated in
Fig. 2. Basically a 5'-square platform, it's of heavy enough
construction to support a light 33' vertical without being nailed
down. Where high winds are often found, however, it's wise to
weight the corners with concrete building blocks or some other
suitable material. Finally, you can install your guy-wire anchors
as shown instead of screwing them into the roof.
Fig. 2. - This is a more elaborate base which
need not be nailed into the roof. Guy-wire anchors can be fastened
to corners as shown.
Either of these two bases should handle almost any type of mounting
situation the average ham is likely to encounter. To keep the
antenna perpendicular on a sloping roof, though, wooden "shims"
may have to be installed under the appropriate corners.
Pole-Line Insulators. Once you've constructed a base, the
next problem is to devise an insulated mounting for the antenna.
The author has found that the "pole-line" insulators in common
use by telephone and power companies serve very well for this
purpose. They are quite inexpensive, and available in many different
varieties and voltage ratings at the larger electrical supply
houses. Moreover, just about any size will handle even a kilowatt
of r.f. with no trouble at all.
Illustrated in the photographs is an antenna installation
designed around a glazed-porcelain unit known to the electrical
trade as a "primary line high-voltage petticoat cross-arm insulator."
The size used here happens to be rated at 6600 volts, but was
chosen primarily for its physical dimensions.
This insulator is mounted on a tapered wooden pin which is
fastened to a platform similar to that shown in Fig. 1. The
radiating element (which is made of 4" aluminum heating duct)
simply rests on top of the insulator, not being fastened in
any way. The guy wires keep the element firmly in place.
Another way of using the same insulator is diagrammed in
Fig. 3. Here the unit rests, upside down, in a circular hole
made in the platform top. The base of the antenna fits in the
cup-like depression formed by what was originally the bottom
of the insulator. Packing the depression with roofing compound
keeps it from filling with rain water.
Fig. 3. - High-voltage "petticoat" insulator
rests, upside down, in platform top to form cup for radiator.
Unused space is filled with roofing compound to prevent rain
water from collecting inside.
Figures 4 and 5 show two methods of employing the heavy "bottle-glass"
insulators favored by telephone companies. In both cases, the
insulator mounts upside down in the platform top, as before
- and an application of roofing compound prevents rain water
Fig. 4. - Here, the arrangement is identical
to that of Fig. 3 except that a telephone-type insulator is
The arrangement of Fig. 4 is similar to that of Fig. 3, with
the antenna base resting inside the "bottom" of the insulator.
The Fig. 5 arrangement is useful in cases where the radiator
is too large to fit inside the insulator. Here, a standard crossarm
pin (or a wooden dowel) is fitted into the insulator and the
radiator mounted on that. If there's too much space between
the radiator and the insulator, the play can be taken up with
a wooden plug, or with four wood blocks, as shown.
Fig. 5. - Ideal for mounting radiator too
large to fit insulator. Any play is taken up with wooden plug
Screw-Base Insulators. A "screw-base service-entrance" insulator,
ordinarily used to terminate a power line where it enters a
house, can also be employed to good advantage (Fig. 6). It comes
equipped with a heavy-duty screw, so there's no problem
in mounting it on your platform. The bottom of the radiator
is then slipped over the top of the insulator-but be sure to
select an insulator large enough so that the radiator is held
well above the grooves, as shown. These grooves are weak points,
and any play in a radiator resting on them will cause a fracture.
Fig. 6. - Service-entrance insulator needs
no mounting hole, screws directly into top of platform.
Another type of screw-base insulator - this time from the
electronic, rather than the electrical, field - makes an interesting
hinged mount for the base of your antenna (Fig. 7). As can be
seen in the diagram, the system uses three radio-antenna lead-in
guides. Consisting of a round porcelain "eyelet" set in a screw-type
wire mount, this kind of insulator is somewhat out-of-date -
but is still available at many of the larger electronics supply
Fig. 7. - Three radio antenna lead-in guides
make a unique hinged mounting.
Two of these insulators (Fig. 7) are screwed to the platform,
the third to a wooden plug over which the bottom of the radiator
is fitted. The two platform-mounted insulators should be spaced
so that hardboard or Masonite washers can be inserted between
the eyelets; these washers prevent the porcelain faces from
grinding against each other.
A galvanized bolt, nut, and washer holds the entire assembly
together. Be sure that the bolt fits loosely in the porcelain
eyelets and that the nut is not drawn up too tightly.
Bottles as Insulators. While not as good a choice as the
types of insulators already described, milk, beer, or soft-drink
bottles have often been pressed into service by ingenious hams.
Such a bottle may be buried - halfway up to its neck - in the
ground, or even set in a small block of concrete. The base of
the radiator is then slipped over the "neck" of the bottle and
held in place by the "shoulder."
Most milk bottles, for example, are just the right size to
hold a radiator made of 2"-diameter raingutter pipe. But, whatever
you do, don't try to mount a radiator inside the neck of a milk
bottle. Even the small "wobble" of a well-guyed mast will cause
it to crack.
Posted April 3, 2014