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/WA9YSD
Date: Sun, 05 Dec 2010 12:54:17 -0600
From: "Dr. Gerald N. Johnson" <firstname.lastname@example.org>
Subject: Re: [TenTec] was OT: Indoor Antenna: re B&W type terminated
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 12/3/2010 10:10 PM, Stuart Rohre wrote:
> Some terminated antennas such as the terminated Beverage are operating
> as a high impedance traveling wave antenna, and thus a resistor to even
> lossy ground would look like a lower RF impedance than the end impedance
> of a long wire. Thus, you could say the resistor to earth is an "RF
> ground" but as a practical matter, it also serves to dissipate static
> charge build up on the antenna wire. A DC ground in that case.
> Those voltages are so high, even a high value resistor to earth looks
> like an adequate "ground". On some resistor terminated antennas, you
> have a value of resistance that does not drain much of your RF.
Typical terminating resistors for Beverage run 600 to 1000 ohms, a lot
higher than a ground rod resistance.
> Examples of this are having 100K ohm resistors to static drain both
> sides of a ladder line fed dipole. The 100k does not pass much current
> if you have an antenna feed impedance of say 1000 ohms.
> but the terminations of the Folded dipole, in the center of the unfed
> wire, have been measured to lose one half the power at some bands.
> Naturally the dimensions of the antenna have reactance terms that can
> in series with the resistor raising the total impedance seen by antenna
> signals. Thus the statement that ast some bands there is less loss.
> -to Rick, I guess the best answer is it depends on the design.
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