LF: RE: 80 meter butternut conversion

[Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>]

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

 

 

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Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens bob@halkirk.org.uk [bob@halkirk.org.uk]
Verzonden: woensdag 8 februari 2012 19:13
Aan: rsgb_lf_group@blacksheep.org
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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