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[TowerTalk] Figuring a coil dimension from N0AH

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Subject: [TowerTalk] Figuring a coil dimension from N0AH
From: (
Date: Thu, 2 Sep 1999 19:51:50 EDT
Greetings all-

I am trying to figure out the size and dimensions of a coil, made from 4AWG 
copper, to bring the resonant point of a vertical down from 3.900MHz to 

I need to figure the size based on a value of 0.5uH...........I'd like to use 
a high Q air wound inductor .....I was referred to look in look in the ARRL 
book for making solenoid coils but cant find it-  

Can someone please tell me what they think the size of the coil should be??  
ie:  The number of turns, the diameter of the coil, and the spacing between 
the coils...........I am planning to just put in line between the antenna 
feedpoint and the feedline- but I'd like to start with a coil in the ball 

Right now, I am just feeding the antenna with any base coil at all-  Most 
resonant point is around 2.2:1 due to impedance match between 50 ohm coax and 
38 estimated impedance of antenna-
Here are the specifics on the antenna:
80 meter vertical
currently resonant at 3.900MHz
Target Freq 3.800MHz
Radiator is 44 feet tall
Radiator is made up of 2 1/8 diameter aluminum radiator tappered up to 1 1/4 
inch at the top
three 20 foot top hat wires at 45 degree angle at 39.5 feet
60 1/4 wave ground radials
Ground mounted  

(I know I can pull out the top hat wires, to let' say a 35 degree angle,  to 
lower the resonant point but I want to try a coil instead)

Any help is greatly appreciated!

73  Paul  N0AH

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