[Top] [All Lists]

Re: [TenTec] was OT: Indoor Antenna: re B&W type terminated dipoles

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] was OT: Indoor Antenna: re B&W type terminated dipoles
From: Steve Hunt <steve@karinya.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Tue, 07 Dec 2010 18:02:09 +0000
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
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.

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

<Prev in Thread] Current Thread [Next in Thread>