My HF Antennes

  • Optibeam OB4-20OWA -monoband 4-element for 20m.
  • Hexbeam 10-15-17-20m. band
  • Inverted L monoband for 40m.
  • Double Bazooka Inverted V for 40m.

 


SWR measured Optibeam 4 element for 20m.band

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SWR measured Inverted L for 40m.band

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SWR measured Double Bazooka for 40m.band

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Hexbeam

We have put off the 12m. and 6m.band from the Hexbeam .
Now we have a better SWR on 10m. the 12m. wire is to close to the 10m.wire.
We have modified the Hexbeam – we downgrade it from a 6-bands to a 4-bands antenne ,but
I think with a better performance then before.

Why we put off 12m.   ???

  • monoband performances are all very similar, as would be expected;
  • the 20m performance is relatively immune to the addition of other bands;
  • the 17m, 15m, 12m and 10m band performance, particularly the F/B ratio, suffers to varying degrees from the addition of other bands. The general trend is that the bands closest (in distance and in frequency) have the greatest effect;
  • the Broadband Hexbeam Gain is generally affected less than the Classic Hexbeam Gain;
  • the biggest performance degradation occurs at 10m when 12m elements are added to the structure.

It is not surprising that there is significant interaction between the 10m and 12m band elements. The “dished” structure typical of most Hexbeams means that the wires for these bands may only be separated by a couple of inches. Modelling shows that if you cannot achieve the 4″ separation between the 10m and 12m wires assumed in these data, the performance will degrade dramatically. The modelling also shows that it is separation at the centre post (where element currents are highest) that matters most; so simply dropping the 10m feedpoint is an easy solution, even though it may result in “sloping” wires. We also saw on the Broadband Hexbeam – In depth page that moderately larger End Spacing does not compromise the performance of the new design, so increasing the End Spacing on a Broadband Hexbeam to allow the 12m wires to be mounted higher in the support structure could be an option.