[TenTec] BUNGEE CORDS

[Jim Brown]

On Thu,1/1/2015 4:41 AM, Rick - DJ0IP / NJ0IP wrote:
> Keeping in mind that height is might, it is a lot easier for one OM alone to
> erect an antenna high in the air when using lightweight components (e.g.
> fiberglass telescoping pole, non-porcelain insulators, thinner Copperweld
> wire, and thinner Kevlar or Dyneema rope), than with traditional heavy metal
> poles and heavy wire and insulators.

Danger, Will Robinson! High antennas  will end up on the ground if one 
of their components is not mechanically robust. UV can quickly degrade 
some of those lightweight components, like the bungees mentioned. 
Several years ago, my good neighbor, an aero/mechanical engineer working 
in the space program, advised me that rope made from Vectran, a new 
space age material, was the ideal support rope for antennas. We bought a 
500 ft spool. it was expensive, $300. I used a length of it to support 
one end of my 160M Tee vertical. That was in early 2012. Last week, I 
was re-rigging that antenna because the big Madrone that held up one end 
had died, and had to be cut down. I had intended to reuse the Vectran, 
but the tree guys used new rope instead. That turned out to be a good 
thing -- upon inspection, the Vectran was badly degraded by UV, the 
antenna would likely have been on the ground in another year, and I 
would have been paying a climber to put new rope through that pulley.

High wire antennas are heavy, mostly because of the long attached 
feedline. Lightweight components ARE a good thing when they reduce 
antenna weight. i like the new lightweight egg insulators, for example 
-- even if they do degrade with UV, the antenna is not going to end up 
on the ground. Some hams use small coax on high dipoles to reduce 
weight, but that small coax adds a lot of loss, so I use RG8 or RG11.

If you don't want a lot of sag (and we don't, because the loss of height 
subtracts dBs from our signal), you need a lot of tension. Again, more 
stress on components, like the center insulator.

"Thin copperweld?"  AARGH -- I HATE copperweld. It's nasty to work with, 
and its brittle. I've never used it. That same neighbor built an 80M 
dipole with copperweld and hung it between two trees at about 90 ft. Two 
days later it was on the ground -- the copperweld broke. He and I have 
since standardized on hard drawn copper, which we buy as a 500 ft spool 
of #8 bare copper from the big box store and stretch to make it hard 
drawn. The process is pretty basic -- we cut it into suitable lengths, 
tie one end to a fixed support (like a telephone pole or big tree), the 
other end to the trailer hitch of his pickup, and pull very slowly until 
it breaks. I first did this about ten years ago, and we've done this 
several times since. We typically get about 20-25% stretch, so that 500 
ft becomes more like 600 ft of #9 copper.

If you don't want to go to that trouble, #12 or #10 THHN (insulated 
house wire) from the local big box store works very well. Yes, copper 
stretches under tension, and I've had to lower and circumcise my high 
dipoles every few years to keep them resonant where I want them. That's 
a major reason I've gone to hard drawn copper.

I like copper split bolt connectors to secure mechanical and electrical 
connections. Solder tends to make a joint brittle, and more likely to 
fail mechanically if subject to movement, and high dipoles DO move. :)

To me, the place for those lightweight components is portable operation, 
like Field Day.

73, Jim K9YC