[TowerTalk] Figuring a coil dimension from N0AH

[Phil Clements]

Four turns, 2 inches in diameter, spaced 1/2 inch apart.
Push and pull the coil like an accordian to vary the frequency.

(((73)))
Phil, K5PC



>
>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
>3.800MHz.........
>
>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
>park-
>
>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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>



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