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Old November 7th 03, 03:34 PM
Richard Harrison
 
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Yuri, K3BU wrote:
"Point by point please." to a list of 7 facts supporting his contention
that a non-uniform current exists in a 1/4-wave antenna with a loading
coil inserted at a spot from 50 to 70% of the radiator length, on Wed.
Nov. 5, 2003, 3:15 am (CST + 6).

1. Coil is warmer at bottom than top.

As power dissipation is proportional to the square of the current, it
shows that in a uniform structure heat is where the current is high.

2. Current indicators at the top and bottom of a loading coil show 40 to
60% difference in ends of the loading coil.

High accuracy may not be available, but the argument is between same
current or dissimilar currents at the ends of the coil. High accuracy is
not needed.

3. Let`s look at the RF choke.

It`s not what the coil is called. It`s position and size with respect to
wavelength.

4. W9UCW used a toroid and got the same results.

The results were based on phase delay, not coil radiation. Antenna
current in a coil results from overcoming an opposition. This impedance
is a vector sum of reactance and resistance. The reactance of the coil
is the same in both directions of energy travel. The impedance the
antenna presents at the ends of the coil is not the same in both
directions.

Any coil reactance produces a delay. Inductors used in telephone
circuits to block audio and pass d-c and low-frequency ringing current
are called "retardation coils". A delay time of the signal is called
"phase lag". These are appropriate names. Toroid coils cause phase lag
too.

5. Cecil explained the reflected wave situation and delay in the
coil---.

Cecil did it accurately and well.

6. ON4UN in his Low Band DXing book for years has shown and explained
the distribution of current in various configurations of loading
coils----etc.

ON4UN did it right and it has stood the test of time. Don`t hold your
breath waiting for revisions.

7. How could it be if the voltage (neon bulb test) is increasing along
the coil towards the top, current has to be decreasing.

Yes, unless the power is increasing in the same direction, and it`s not.
The neon shows high potential gradient points. In the driven
quarter-wave radiating element, loaded or unloaded, the maximum voltage
always seems to be at the tip end.

We know that as in a transmission line, in a standing-wave antenna,
reflection produces current maxima at voltage minima, and vice versa.

Yuri shouldn`t bemoan lack of response to his Antenna Group 7. It only
shows there is not much to contradict.

Best regards, Richard Harrison, KB5WZI

 
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