by John Reisenauer, Jr.
KL7JR/K7ICE
When I came across a close-out deal on golf ball
retrievers, you know the telescopic metal variety with a small cage on one
end for retrieving golf balls out of water traps, I immediately knew what
my next antenna project would be.
At $6 each and 15 feet long when
fully extended, the aluminum beauty tapered down into four sections from
.75 inch to about .25 inch in diameter making it ideal for multi-band
portable use. I remembered a previous article in QST where a vertical was
made from a telescoping paint pole. I never could find one on sale so
opted for this lighter version "look-a-like" that was easier on my wallet.
While I was at it, I designed a drive on base support made from scrap
lumber and PVC pipe to go along with my new vertical (large rocks or other
heavy items will also work in-lieu-of a vehicle). Besides a few wood
screws and hose clamps, I had less than $10 invested in the antenna.
I've experimented with verticals made from copper pipe or EMT over
the years, so I knew this set up would also be an excellent performer on
10 through 20 meters.
Erecting the antenna was pretty simple and only took
about 15 minutes. After all four sections were extended, I jumpered across
each section's plastic collar (see photo below), with a short piece
of #12 stranded wire and two hose clamps and added an 18 inch long whip
made of .25 aluminum tubing (a metal coat hanger or stiff wire cut to
length also works!) to make the antenna 16 ft-4 inches, or .25 wl on 20
meters (234 divided by frequency in MHz).
Next I slid the antenna
down into the base and connected the coax and ground radials (note the
ground ring made from plumbers tape). See photo below. Alligator clamps
work fine to terminate the radials to the 12 inch diameter ground ring. I
like to use battery post clamps on the coax (center conductor of coax to
pipe and braid to ground ring). I usually have good success with just 4-6
radials but you may want to put out as many as you can (I use 16 ft. long
each as a minimum). I always toss one radial in the water if I'm near a
river, lake or the sea to enlarge the ground plane and reduce QRM.
I used my 15 foot long vertical with the 20m whip also on 17
and 15 meters with good results. You can easily retract the antenna to the
proper length for use on 10 and 12 meters (about 8 ft-3 inches and 9 ft-4
inches respectively).
Photos of
construction:
Left
photo, complete antenna set up. Right photo, Jumper on telescopic
section.
Quickie
homebrew base from scrap lumber with ground ring and coax
connections
Casual operating during a May
2006 weekend of poor to fair band conditions, I worked 32 states plus
Mexico and Italy on 20 meters, 19 states on 17 meters and West Africa and
7 states on 15 meters. Even though 10 and 12 meters were dead, I feel like
I hit a hole-in-one with this aerial! KL7JR, John.
