Ron D'Eau Claire wrote:
Vic, K2VCO, wrote:
Keep in mind that you are measuring the current in the radiator AT A
PARTICULAR
POINT.
---------------------
The counterpoise is tuned for maximum current at the *rig*!
The idea is that the more current flowing into the counterpoise for a given
power output the lower the RF voltage at the rig. The objective is to
provide the lowest impedance "RF Ground" at the rig.
Hi Ron,
I agree.
The post I was responding to included:
For example, on 40 meters the use of a counterpoise helped
to realize a substantial increase of current into the radiator, while on 80
meters I actually saw more current into the radiator with the counterpoise
unhooked on that band. The effects on 30-10 were really fairly minimal or
neutral in this regard.
Mychael was using an RF current sensor to measure current into the radiator. My
point was that tuning the counterpoise may have the effect of moving the high
current point in the antenna system that includes the counterpoise and the
radiator. I was making the point that his experiment of unhooking the
counterpoise and measuring the current into the radiator did not indicate that
the counterpoise was or was not improving antenna performance.
Since his antenna was an unbalanced end-fed wire working against ground, the
counterpoise was an essential part of his system. Tuning it would be expected
to have an effect on performance. Of course, with a balanced or
ground-independent antenna, no counterpoise should be needed. RF in the shack
is indicative of imperfect balance or isolation.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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