[Antennas] Feedline spreaders update II

[Steve L.]

Yet another update on the ultimate open-wire
transmission line spreader material.

I finally found the black irrigation tubing in 3/8"
(I.D.) at a commercial nursery supply store. $4.95+tax
for a 50' roll. The whole 50' roll is so lightweight!

In about five hours I cut and drilled the whole 50'
roll, made 240 spreaders, good for 300' of
transmission line (15" spacing, 2" wire spacing, Zo =
500 Ohms w/ Hard Drawn, 7-strand solid copper 14AWG
wire). I run legal limit on 160-10.

This is how I made it:

1) I use 2" wire spacing and 2.5" spreader lengths
2) I set my calipers to 2.5", use the pointy end and
make a mark in the material every 2.5" - it's easy.
3) Using a decent pair of scissors, I cut the tubing
on the marks. With scissors!
4) Using my calipers set to 2.0", I take each cut
spreader and use the pointy ends of the calipers to
make two marks (2" apart), centered on the spreader.
5) I drill the spreaders at each mark using a 0.093"
drill bit - for 14AWG wire.

Interestingly, the material self-heals a bit so the
drilled holes close up some. When you push the wire
through, it goes easily enough but the material GRIPS
the wire... no kidding, you might not even need hot
glue, they tend to stay very well all by themselves.

For vertically hanging phasing lines you can probably
go with 18" spacing but it seems very stable with 15"
spacing for everything.

When cut into 2.5" lengths, it's plenty stiff, strong
and has hardly any of the 'curl' left from being
stored in a roll - each spreader is almost perfectly
straight. I unrolled it and let it sit overnight, laid
out flat, with each end held down by a cinder block.

I'm sure some of you will want to use a wider spacing
or insulated wire or whatever. I drill two holes and
thread the spreaders onto the wire because it's super
stable -- certainly NOT because it's easier or faster
to do!

This stuff passes the microwave test.

So, I'll be replacing all my windowed ladder line with
this - it's lighter, cheaper, is less visible and has
far less wind drag. MOST importantly, it doesn't
change between wet and dry like windowed ladder line.
I'll use the windowed stuff on my Field Day antennas.

73, Steve N4SL Snohomish, WA CN88


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