[TowerTalk] Grey PVC Loading Coil

[Terry Conboy]

At 01:45 PM 2006-12-05, WA3GIN @ Arlington County, VA wrote:
>I think the voltage concern is going to be at the top of the antenna but
>I could be wrong.
>
>The electrical (gray) PVC holds up well outside in UV.  But one can
>always paint the plastic black which will protect it from the UV.  At HF
>the plastic is invisible for the most part.
>
>Get the thing tuned up and paint the whole thing black and you're good
>to go as best I can tell.

With 1500 watts to Dan's 40 foot vertical on 160m (assuming 10 ohm 
equivalent ground resistance), the voltage across the loading coil 
would be about 9.5 kV rms.  That drops to only 2.5 kV rms at the 100 
watt level.  Maybe Dan should install a tiny thermometer on his PVC 
coil form and tell us how hot it gets.  8-)

BTW, my model shows 56.4 watts in the ground and 29.3 watts in the 
coil (Q=200) with 100 watts to the feedpoint.  The other 14.3 watts 
should radiate just fine.  That's about 8.4 dB loss if you're keeping 
score.  (And 14.3 watts more than I can radiate on 160m!)

73, Terry N6RY