[TowerTalk] Multi-band dipoles

[Rik van Riel]

On 04/21/2011 11:38 PM, Joe Subich, W4TV wrote:

> Most reputable (commercial) manufacturers of the terminated folded
> dipole for military/government service give "gain" specifications
> ranging from -1 to -4 dBi in free space and efficiency ratings of
> 15% to 50% (30% average).  Such performance is equivalent to turning
> 1 Kw to 250 watts ... or a barefoot 100 W rig into a 25W pea whistle
> on most bands (and even worse on 160 or 80 meters depending on the
> antenna size).
>
> While such performance may be fine for military/government use with
> frequency agile, high power ALE circuits, or in short range NVIS
> applications, the terminated folded dipole belongs in the same
> category as the Isotron, cross-field, and fractal antennas for
> amateur purposes.

It works great with ALE, because the radio automatically
picks the path with the best propagation.  Losing 6dB in
the antenna is no big deal, when the radio reduces the
propagation losses by 20dB over whatever random frequency
a radio-untrained soldier might otherwise pick.

For amateur use there really is no need to choose such
an antenna, since the ham frequencies are largely
harmonically related.

We do not need frequency agility over all of HF.

-- 
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