Theoretical efficiency is usually figured as if the antenna is in free
space, but of course it isn't. Height above ground, ground characteristics,
surrounding objects, etc., all must be taken into account.
73 Ray W2RS
In a message dated 12/7/2010 3:12:29 P.M. GMT Standard Time,
geraldj@weather.net writes:
On 12/7/2010 5:58 AM, Jim WA9YSD wrote:
>
> Any antenna for that matter looses 1/2 their power or more when operated
on a
> band that it is not designed for.
Why do you say that? I don't agree. It may not radiate in the direction
it did on the fundamental. The system may loose power from matching
network losses when the impedance is obnoxious to match, and the really
short antenna looses radiation efficiency.
>
> Efficiency for a folded dipole has a factor of around 0.98
> Efficiency for the common dipole is about 0.1
Nah, there's no reason the common dipole should be poorer than the
folded dipole.
> Efficiency for the Double bazooka is about 0.89
Balderdash. The double bazooka is no better than a folded dipole and has
no significantly greater bandwidth except what comes from the fatter
radiator ends of shorted together twin lead. It suffers from having tiny
conductors encased in insulation that make it structurally weak in wind
and ice. If cross connected at the center instead of the original series
connection, the two quarter wave coax stubs do compensate for reactance
changes and give that variation a greater impedance bandwidth. But its
still wimpy and breaks all the time in the real world.
>
> Efficiency for the above cases is its ability to couple. So your use of
the
> word efficiency must be defined better so it is not so confusing as to
what
> exactly your talking about.
>
>
> Stay on course, fight a good fight, and keep the faith. Jim K9TF/WA9YSD
>
> -----------------------------------------------------
73, Jerry, K0CQ
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