[Antennas] windowed ladder line vs. true open wire line

Thu, 6 Feb 2003 20:32:35 -0800 (PST)

On the subject of balanced transmission line, I have
used 1000's of feet of commercial 450 Ohm windowed
ladder line over the past ten years on 160-10m. The
lines I've used have 14AWG stranded copper clad steel
wire - they are very strong, very lightweight and
withstand the weather extremely well. They don't age,
crack, get brittle, etc.
HOWEVER, at the transmitter end the Z changes quite a
bit from dry to wet (much more noticeable on 10m and
15m) so if the antenna you are using has a sharp tune
(narrow bandwidth) you will be tuning and re-tuning as
it starts to rain, rains heavier or starts drying.
I've tried cutting every-other spacer out with a pair
of scissors and I've rubbed pure carnuba wax on it to
reduce the effect, but it's still fairly pronounced.
I've found this to be a pain and I'm in the slow
process of replacing all my windowed ladder line with
homebrew true open wire line. It's a LOT of line. I
use 14AWG 7-strand hard drawn copper wire with 1/2" OD
CPVC for spreaders. I space mine 2.25" and use a
spreader every 20" for vertically hanging line and
every 16-18" for line that has to bend or run long
distances horizontally. The spacing is whatever you
need to keep the wires from crossing, twisting, etc.
It doesn't change at all with wet/dry condx unless the
wires ice up and it handles legal limit on RTTY (100%
duty cycle) without a wimper.
So, keep this in mind. The windowed ladder line is
very good otherwise and I use it on my Field Day
antennas and temporary antennas for ease of
installation and to save time.
If you are putting up a 160-40m antenna, you will
hardly notice this effect but on 15 and especially 10m
it's a bugger.
73, Steve N4SL
73, Steve N4SL
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