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LF: RE: 80 meter butternut conversion

from [Rik Strobbe] [Permanent Link][Original]
To: "[email protected]" <[email protected]>
Subject: LF: RE: 80 meter butternut conversion
From: Rik Strobbe <[email protected]>
Date: Thu, 9 Feb 2012 16:46:45 +0100
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Acceptlanguage: nl-NL, nl-BE
In-reply-to: <4F32BB33.000032.01064@BOB-PC>
References: <4F32BB33.000032.01064@BOB-PC>
Reply-to: [email protected]
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Thread-index: Aczmjb2y9X9Cgr0IQPCQMW6zZ7XrpQAstepI
Thread-topic: 80 meter butternut conversion
Hello Bob,
 
as the antenna itself is resonant well above 136kHz it will have a very large capacitive component at 136kHz.
Assuming it is a HF2V the antenna is a 10m vertical contruction, so using the 6pF/m rules the antenna capacitance will be about 60pF. This means a reactance of about 20kOhm (at 136kHz) and a coil of 23mH will be needed to bring the antenna to resonance at 136kHz.
Although this is possible, such a large coil will be rather lossy (100 Ohm at a Q of 200) and will cause a very poor efficiency. It will also cause very high antenna voltages during transmission, with possible arcing problems.
I believe that Andy (G4JNT) is using a small antenna with similar dimensions on 136kHz you he maybe best to give you a "how-to".
 
73, Rik  ON7YD - OR7T
 
 
Van: [email protected] [[email protected]] namens [email protected] [[email protected]]
Verzonden: woensdag 8 februari 2012 19:13
Aan: [email protected]
Onderwerp: LF: 80 meter butternut conversion

hello
I have a 80m butternut antenna how can I adapt this to resonate at 136 khz.
 
regards bob MM0RJR
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