I'm puzzled by most of what Jim wrote.
"Efficiency" is a term well understood by most professional engineers
as: Efficiency = Pout/Pin
If we are talking specifically about an antenna's efficiency - not an
antenna *system* - the expression becomes:
Efficiency = (Radiated Power)/(Power input) = (Power input -
Losses)/(Power input)
The only losses in a simple antenna are I^2*R losses in the element(s).
If we take a resonant 20m half-wave dipole constructed from #14 wire,
its efficiency is about 98.5% (-0.06dB); if we operate the same antenna
on a different band - say 17m - the efficiency improves to 98.9% (-0.05dB).
The efficiency of a Double Bazooka will be lower than that of a
half-wave dipole because of extra losses in its coax stubs.
73,
Steve G3TXQ
On 07/12/2010 11:58, 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.
>
> Efficiency for a folded dipole has a factor of around 0.98
> Efficiency for the common dipole is about 0.1
> Efficiency for the Double bazooka is about 0.89
>
> 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/WA9YS
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|