Topband: Effect of trees touching inverted L

[Guy Olinger, K2AV]

>From K9SGQ:

I was looking for real world experiences on how severe the problem is 
when an
insulated antenna wire touches a tree limb.

------

Two considerations that bear:

1) There is likely to be wear of the insulation. Teflon will likely 
last best in such a situation, but will eventually succumb if laying 
across a branch, due to constant abrasion. Further, sunlight and 
weather will weaken some insulation, accelerating breakdown.

2) Breakdown will occur quickest with QRO and quickest if the touching 
is near a voltage high. Voltage at the ends of a dipole (or unfed end 
of endfed wires) can be surprisingly high, well into thousands of 
volts, even running 100 watts. Some insulating material will not 
withstand QRO at a voltage point and breaks down immediately.

If the touching is occasional, I have had success with a layer or two 
of teflon on the wire in the area where touching can happen.

I currently have a supply of silvered stranded #12 with teflon 
insulation, and get the second layer with high temp teflon shrink 
tubing.  I have run that right through thick bushes without problem, 
and at QRO levels. This is not a wire for strength however, and will 
not substitute in a situation that calls for copperweld. I only use it 
where contact is expected.

Teflon insulated wire can be seen on eBay from time to time at 
reasonable prices. Just search on "teflon" and "wire".

73, Guy.





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