[TowerTalk] Wire size for 800 meter long wire

[Michael Tope]

----- Original Message ----- 
From: "Barry Merrill" <barry at mxg.com>

> I've got a distance of 2400 feet for the long wire 
> between two 70 foot high bluffs on opposite sides
> of a saltwater inlet that is shoaled and un-navigable.
> 
> I plan on 100 watts, and I'd like to use small wire to
> make the wire less visable, but using the maximum 
> SPAN of 1000 feet with #12 wire, the chart says that
> to keep the sag less than 50 feet, I need 400 pounds 
> of tension (as if I could every supply that force!),
> but the recommended #12 tension is only 75 pounds.


Barry,

Have you thought at all about how you are going to feed
the long wire? Very long end-fed wires get very directive
off the ends. We had a 600 footer at Ohio State (up ~100
ft). It ran east-west and worked great toward Africa on 75
meters (it was fed from the West end) - a guaranteed pileup
buster to West Africa on 75 meter SSB. On 40 meters it 
didn't seem to work any better than a high dipole. The 2 
element quad at 110' feet ran circles around it on 20 meters. 
Given the engineering challenge of spanning a 1/2 mile inlet, 
have you considered other alternatives. I would certainly 
model it before going to that much trouble. 

How about a sloping wire from one bluff down into the inlet 
at about 45 degrees using a heavy anchor to hold the bottom 
end in place? If your primary interest is shooting towards the 
saltwater, I would want to be vertically polarized. 

73 de Mike, W4EF............................