Counterpoise is required for most antennas to operate "effeciently" (have
you ever tried to load a 1/4 wave whip (without one)? Makes great dummy
load! Dont radiate worth a darn! Needs the full "1/2 wave" to radiate
effectively say that as can be done with loading coils, ect to shorten the
effective length, or a ground media for the 1/4 part to work against (tho,
at vhf there are SOME 1/2 wave , base coupled antennas that need no counter
poise-- but then talking 75 meters- 125 foot tower to do that!!



Cecil wrote:
Jim wrote:
And, one other idea !! (found on the bay of "e"), and available
elsewhere-
a mount for 2 of these (or the hustler, and an Iron Horse, ect) "1/4"
wave
antenna -- first antenna goes to center of coax, second goes to shield!!
makes a dipole, about 15 foot long, and can be mounted to mast
(conductive,
or plastic, same diff! tho the impedence will be quite low (because of
these loaded
whips), and the effeciency will be also not the best, at least would be
an
effective counterpoise!! and, to boot, parts available to build adaptor
at
rip-off shack!! got whole thing off epay for about 50 bux, +
shipping!!
Jim NN7K

What do you consider to be the purpose(s) of a counterpoise?
--
73, Cecil http://www.qsl.net/w5dxp



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George,
It does that every half cycle...
'Doc

On Thu, 6 May 2004 22:04:39 +0100, "Neil Gibson"
wrote:

I have a Hustler amateur mobile antenna model RM-80 for 80 Meter 25-30 KHz.
Although it was designed as a mobile I want to use it as a portable, can
anybody tell me the length of the counterpoise needed for this model? or can
I just use an earth wire


Use another RM-80 as the counterpoise.


Ron

Ron wrote:
I have a Hustler amateur mobile antenna model RM-80 for 80 Meter 25-30 KHz.
Although it was designed as a mobile I want to use it as a portable, can
anybody tell me the length of the counterpoise needed for this model? or can
I just use an earth wire

Use another RM-80 as the counterpoise.

Hmmmmm, a 2% efficient antenna with a 2% efficient counterpoise. :-)
--
73, Cecil http://www.qsl.net/w5dxp



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Hey Cecil, 4% is better than 2%, and a 'hunerd'% increase
in efficiency!
(I agree with you anyway...)
'Doc

'Doc wrote:
Hey Cecil, 4% is better than 2%, and a 'hunerd'% increase
in efficiency!
(I agree with you anyway...)

A 2% efficient radiator and a 2% efficient counterpoise
doesn't add up to 4% total efficiency. :-)

Anyone who wants a portable rotatable dipole on 75m can
do much, much better than two Hustlers. Two SD-20 poles
with high-Q loading coils in the middle of each comes to
mind. And that's not much more trouble than two Hustlers.
The SD-20 approach is available at http://www.wr6w6.com
--
73, Cecil http://www.qsl.net/w5dxp



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On Sat, 08 May 2004 13:51:15 -0500, Cecil Moore
wrote:

'Doc wrote:
Hey Cecil, 4% is better than 2%, and a 'hunerd'% increase
in efficiency!
(I agree with you anyway...)

A 2% efficient radiator and a 2% efficient counterpoise
doesn't add up to 4% total efficiency. :-)

Anyone who wants a portable rotatable dipole on 75m can
do much, much better than two Hustlers. Two SD-20 poles
with high-Q loading coils in the middle of each comes to
mind. And that's not much more trouble than two Hustlers.
The SD-20 approach is available at http://www.wr6w6.com

The question was the length of a counterpoise, not a rotatable dipole.
I figured another Hustler sure beats running radials out in a portable
situation.

If someone was to ask you how to make their Chevy run better would you
tell him to get a Ford? ;-)

Ron

On Sat, 08 May 2004 09:12:50 -0500, Cecil Moore
wrote:

Ron wrote:
I have a Hustler amateur mobile antenna model RM-80 for 80 Meter 25-30 KHz.
Although it was designed as a mobile I want to use it as a portable, can
anybody tell me the length of the counterpoise needed for this model? or can
I just use an earth wire

Use another RM-80 as the counterpoise.

Hmmmmm, a 2% efficient antenna with a 2% efficient counterpoise. :-)


Hmmmm, I wonder what 2% efficient means. 2% radiated power with 98%
reflected back into the radio? Ability to contact only 2% of the
stations that you can receive? What?

Ron, W1WBV

Ron wrote:

wrote:
Hmmmmm, a 2% efficient antenna with a 2% efficient counterpoise. :-)

Hmmmm, I wonder what 2% efficient means. 2% radiated power with 98%
reflected back into the radio? Ability to contact only 2% of the
stations that you can receive? What?

It's a ballpark estimate and means for every 100 watts going
into the antenna, two watts are radiated. If the feedpoint
impedance is 50 ohms, 98 watts are dissipated as heat in
the antenna, primarily in the coil(s). (Try transmitting 100w
into a 75m hamstick for one minute and then grabbing the coil.)
--
73, Cecil http://www.qsl.net/w5dxp



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Taking Cecil's example a step further. The radiation resistance [Rr] of
an 8 foot antenna at 3.9 MHz is in the range of 1 to 2 ohms depending
upon coil location. The antenna losses, I^2*R, can be in the range of 10
to 20 ohms [Ra], and the ground losses can be in the range of 10 to 20
ohms {Rg]. So, your nominal '50 ohm load' is comprised of Rr + Ra + Rg = RL.

Efficiency is (Rr/RL)*100%. So, 2/50 = 4% or 1/50 = 2%. Take your pick!

The energy is NOT reflected back. It is wasted as heat in the antenna
and ground losses!

Deacon Dave, W1MCE
+ + +

Ron wrote:

On Sat, 08 May 2004 09:12:50 -0500, Cecil Moore
wrote:


Ron wrote:

I have a Hustler amateur mobile antenna model RM-80 for 80 Meter 25-30 KHz.
Although it was designed as a mobile I want to use it as a portable, can
anybody tell me the length of the counterpoise needed for this model? or can
I just use an earth wire

Use another RM-80 as the counterpoise.

Hmmmmm, a 2% efficient antenna with a 2% efficient counterpoise. :-)



Hmmmm, I wonder what 2% efficient means. 2% radiated power with 98%
reflected back into the radio? Ability to contact only 2% of the
stations that you can receive? What?

Ron, W1WBV