26 August 2015
Isoon discovered that most metallic objects a few feet in length made good enough antennas to bring in the closest
AM station. Attaching the second alligator
clip to metal that was “grounded” or in
contact with the earth improved signal
strength and brought in weaker signals.
Those childhood “experiments” soon
taught me that some metal objects were
much better antennas than others, and that
bigger metal was not always better. I have
never forgotten the anticipation and
excitement of attaching alligator clips to new
materials and then hearing the results through
I was hooked. The fascination of signaling
through space without wires would become
my primary hobby for the next half century.
While writing this article, I realized I have
actually been experimenting with antennas
since I was in elementary school.
Later in life, I studied electronics and
then electrical engineering. I learned about
resonance and how radio frequencies have
electrical wavelengths. Around 1969, I got my
first ham radio license.
Over the last 45 years, I have built
dipoles, ground planes, J-poles, quads, yagis,
quagis, delta loops, and long wires. In
addition to the traditional copper wire, I have
cobbled them together using EMT and rigid
aluminum conduit; copper, aluminum, and
stainless steel tubing; brass welding rods; and
even barbed wire. I have also used antenna tuners to load
up bedsprings, fences, house wiring, abandoned
telephone line, umbrellas, farm wagons, aluminum gutters,
and tin roofs.
Just as other sculptors are blessed with the vision to
see their works of art hidden in wood and marble, I have
developed the ability to see antennas hidden in metal.
After working with antennas for a while, I
believe most everyone can probably develop
an eye for dimensions that are quarter-wave
multiples of their favorite frequencies.
A couple of months ago, my wife had an
accident that injured her right foot. X-rays
confirmed bones were broken, and an
orthopedic surgeon sent her home with a cast
and a set of shiny, new, adjustable aluminum
When all the medical excitement was
over, I had time to take a closer look at her
hobbling around on those crutches. That’s
when I spotted the six-meter antenna hidden
in them. A few minutes with the tape measure
not only confirmed the 6M antenna, but also
discovered a 4M dipole. All I needed to do
was get the wife healed up and the crutches
would be mine.
Eventually, the broken bones did mend
and the crutches became surplus to her. That
made them prime material for a novel
antenna that would also become an eye-catching conversation piece.
My particular set of crutches happen to
be rated for 300 pounds. Each crutch has two
separate adjustments. The upper section has
three settings 5-1/2 inches and 6 inches apart.
The lower section has 13 positions in one
inch increments. Refer to Figure 1.
When everything on one crutch is
extended to its maximum length, it measures
approximately 60 inches. Certainly long
enough to make a 112 inch 6M dipole!
Compressing all the adjustments reduces the same
crutch to 36-1/2 inches. Plugging these dimensions into
the old standby dipole formula (468/MHz = inches)
indicates half-wave resonances from about 47 MHz to 78
MHz. Great! Now, all I needed to do was find a way to
put the two crutches together and feed them with coax.
■ FIGURE 1.
2 Adult size aluminum crutches
6" 3/4" ASTM D 2241 PVC pipe (The ID of schedule 40 PVC was too small to work on my crutches.)
1 1-1/2" Schedule 40 PVC tee
2 1-1/2" x 3/4" PVC reducing bushings
2 #8-32 x 3" Machine screws
6 #8-32 Hex nuts
4 #8-32 Flat washers
2 #8-32 Star lock washers
2 #8 Crimp type ring connectors suitable for use with the size coax cable used to feed the antenna