Archive for September, 2014

HF Antenna Work

September 16, 2014

The tower here at home in Ohio was erected by the previous owner. The house was built
in 1976. Some of three-section tower rungs had rusted through. It was time to take it down.
Unfortunately, I was not anxious to replace it at today’s costs. It held the center of
my 40/80 meter dipole about 24 feet above ground , and could be lowered by a rope and pulley.
The east end slanted upwards into a tree. The west end was tied to a 15 foot post.
Some local hams volunteered to take down the tower, so down it came! The dipole was tied
off to the tower support on the side of the house. The dipole was still on the rope and pulley,
so I could lower it nearer the ground. I lowered it to inspect the center insulator and wire.
Inspection showed the 20 plus year old antenna needed replacement.
I had some like new 14 AWG 7 strand copper Clad steel wire in storage. The old handbook formulas
indicate each leg should be 62.4 ft. long. (Resonant at 3.75 MHz, right in the center of the band).
I cut two wires about 63+ ft. to allow for tying the ends. My tuner can compensate for the actual
operating frequency and I like both CW and Phone.
I temporarily hoisted the antenna and went to the shack to check the SWR on both 80 and 40
meters. I use an MFJ 259B Antenna Analyzer to check SWR before applying transmitter power. The
SWR was tunable to very low values on both 80 and 40 meters!
It has been over a month since the tower came down. In almost daily use on day-time 75 phone,
the results of the lowered height trap-less dipole have been most satisfactory. Operation has
always been at 200 watts output or less. Be sure to clean and solder or otherwise secure a good
electrical connection at the center insulator. Order some “COAX-SEAL” (www.CoaxSeal.com) to
waterproof your connection. Find a couple ceramic egg-shaped end insulators for the ends of your
antenna.
If you are new to HF, please consider the adventure. It is a wonderful part of the Amateur
Radio experience.
Please note I not an expert at anything, other than growing older. Enjoy this hobby and
“be careful out there”. 73 Glenn Brown for Pastime Projects.