Joint conductivity does make a difference-at least in my experience with
Universal
Towers. I've had aluminum towers up at various locations since 1976. Currently,
I have an 80 Footer
with a 30" base and TH6DX on top, shunt fed on 160. Last winter,
the SWR went up significantly and performance seemed to go down.
After fiddling with the matching system for several hours, I decided to measure
the resistance of the gamma wire to ground. It measured over 4 ohms (tap at
48 feet).
I finally took my digital ohmmeter outside and found the high
resistance at the first section joint - 4 ohms! I made straps out of thin scrap
aluminum and fastened them across the joints with stainless steel hose clamps.
Problem solved and antenna
performance back where it was before. I highly recommend checking joint
resistance
if you are having a problem adjusting
the gamma match on your shunt-fed tower.
73, Dennis W0JX Milan, OH
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