I have two bidirectional 720 ft beverages that use 450 ohm ladder line,
oriented NE-SW and NW-SE. The ladder line is supported by 4x4 wood posts,
about 7 ft above ground, spaced every 60 ft. The antenna works well, but has
turned out to be a maintenance nightmare. My first mistake was to anchor the
ladder line to the top of each 4x4 post using little plastic clamps (DX
Engineering). Those lasted about a week before being pulled apart by the
wind. I replaced them with wood pressure plates screwed down over the ladder
line with 2" lag screws into the top of the posts. Those lasted about a year
before cracking and splitting. The ladder line turned out to be very
fragile. The plastic material gets brittle and cracks, and the wind causes
metal fatigue and eventual failure of the strands.
I've spent the past three afternoons patching up the beverages for the
winter DX season and am only about half done.Yesterday, I thought I had
everything fixed and only needed to phase the ladder line properly. I left
one wire open and grounded the other wire at one end, and then used a DMM to
identify the grounded wire. To my dismay I found an open circuit on both
wires. A spent a couple of hours with a toner trying to find the break, but
to no avail. Then, it occurred to me that my Fluke 87-V DMM may be giving me
erroneous readings. I replaced the Fluke with my trusty Simpson 260 and
discovered the wire was actually intact. Evidently, the Fluke's sensitive
solid state ohmmeter circuit had been overloaded by the
inductance/capacitance of the ladderline or possibly RF pickup. I should
have known better from the get-go.
So now, I've got one of my beverages working and will start repairs on the
2nd one. I've decided ladder line is a terrible choice for a beverage
antenna, at least in New Mexico, where there is intense UV sunlight and
windy Springtimes. My plan is to replace the ladder line with parallel
strands of 12 AWG copperweld wire, with pass-through insulators on each 4x4
post, and the wire anchored at each end. I'll use turnbuckles to adjust the
tension. I'm really tired of repairing the damn antennas, and my feet hurt
from hiking back and forth to each end.
73,
Jim W8ZR
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Topband Reflector