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[Towertalk] Matching unit for 1/2 wave verticals

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Subject: [Towertalk] Matching unit for 1/2 wave verticals
Date: Thu, 8 Aug 2002 02:22:39 -0000
Hello to all and Hello to Dink,

How this all started:
A few days ago Dink, N7WA requested information on the possible interaction
of closely spaced full size 1/4 wave verticals for 80 and 40 meters. I
suggested to put up a single vertical for 80 meters and feed it as a 1/2
wave vertical on 40 meters.

Dink, N7WA is having trouble finding the information on how to do this so
here it is. The values are taken from ON4UN's Low Band DXing first and
second edition.

One capacitor and one coil are needed which are in series with each other.
The configuration is called a tank circuit.

     *  Point going to antenna
    *                 *
   C                 C
   A                 O
   P                  I******** Tap To Coax To Radio
   A                 L
   C                 *
    I                 *
    T                *
    O               *
     R               *
             * Ground or radials and shield of coax


BAND          C          L
40M            40pf       13uh
80M            80pf        24uh
160M          160pf      49uh


BAND           C                    L
40M               250pf             1.9uh
80M               500pf              3.8uh
160M              1000pf            7.6uh

I can't seem to locate the formula for the voltage being produced but it is
very high. I believe it to be around 10,000 volts for 1500 watts output. I
believe the High-C configuration will be less loosely do to the small values
used in the coils. I have only used the High-L values for 160 meters.

Rich AA2MF

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