At 03:32 AM 2005-03-25, Clive Whelan wrote:
>I have made and erected a 15m Moxon using the dims. from W4RNL's site. The
>construction ( a prototype) consists of a small (1x1 metre) X of 20x20mm Al
>angle, supporting bamboo canes to about 9ft ( sorry about the mixed units!),
>and then 1mm wire ( probably about AWG14G?) stretched around. The trial
>height is only about 20ft. The performance is disappointing; that is to say,
>if it were a rotary dipole at 20ft I'd be pleased, but there is no f/b (
>fixed N/W for the trial), and certainly no fwd gain ( cf a simple vertical).
>In fact, I suspect-if anything- it is firing off the back, as the 5Z4 beacon
>is a cracking signal, being well up on the vertical. Checking with the MFJ
>analyser, I was shocked to find it resonant at around 20.25Mhz- this would
>be consistent with the reflector acting as a director, but with very poor
>efficiency. So, we took the whole thing down, and double checked everything,
>finding no errors. Now something even more puzzling. Checking further HF
>with the MFJ, I find sharp "resonances" around 63 and 106Mhz, being roughly
>the third and fifth harmonic of an in band 21Mhz resonance, but which does
>not occur at the fundamental frequency, as described above.
Clive,
Are you using bare wire? If not, that could account for the low resonance.
73, Terry
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