[TowerTalk] Grey PVC Loading Coil

[WA3GIN in Alex. City, VA]

I run 7 watts into a 50ft center-loaded helical and use a common MFJ tuner
to match the input. I have gotten good reports from stations as far as
Ontario, Canada.  He might do just fine with 14 watts.

73,
dave
wa3gin


-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Terry Conboy
Sent: Tuesday, December 05, 2006 5:38 PM
To: towertalk at contesting.com
Cc: wa3gin at erols.com; n3ox at n3ox.net
Subject: Re: [TowerTalk] Grey PVC Loading Coil

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 

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