[Antennas] Effect of surfactants in water on ladder line, dielectric properties

2002年12月17日 20:15:23 -0600

A few more observations......
I picked up another roll of #551 window ladder line and found
that new ladder line beads very well. Older window ladder line
(I think the stuff I was using spent 3-5 years in the air) beads less
but this can be easily overcome by using silicon spray (safe for
polyethylene) but I don't know how long it lasts in the sun. The 
dielectric effect of the silicon spray is nil.
The use of wetting agents for "testing a wet transmission line"
seems to give unnecessarily bad loss data and, I now believe,
is not representative of even old weathered window ladder line.
Since transmission line capacitance changes are an indication
of dielectric properties (and loss changes) and are very easy to 
do, here is some recent data. The idea is to get the smallest 
change in capacitance ...then do power loss measurements. The 
capacitance checker operates at some low frequency in the 
KHz range and higher frequency effects will be worse.
NEW #551 DRY................................................... 2.96
pf/ft
NEW #551 WET distilled water (approx rain)... 3% higher 
NEW #551 WET tap water................................... 5% higher
NEW #551 WET wetting agent ........................... 55% higher
OLD #551 WET wetting agent .......................... 248% higher
OLD #551 (Mod) DRY......................................... 2.91 pf/ft
OLD #551 (Mod) WET distilled water............... 11% higher
OLD #551 (Mod) WET wetting agent................. 29% higher 
OLD #551 (Mod) DRY w/silicone........................ 2.91 pf/ft
OLD #551 (Mod) WET w/silicone, distilled water 6% higher
The (Mod) is #3 per previous note removing most of the 
web, that's why the effect of the wetting agent is reduced.
73 Kees K5BCQ