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Old March 14th 06, 05:25 PM posted to rec.radio.amateur.antenna
Richard Harrison
 
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Default Current through coils

Cecil, W5DXP wrote:
"Kraus agrees."

Pity the fool that argues with Terman or Kraus!
In Kraus` Figure 14-2 of the 3rd edition of "Antennas", the 1/2-wave is
resonant and shows no phase shift from end to end. In Figure 14-4, phase
is shown to make an abrupt phase transition at a point 1/2-wave back
from the open circuit at the tip of the antenna. This is predictable
from the behavior of an open-circuited transmission line as shown by
Terman in Fig. 4-7 in his 1955 edition.

Kraus` Figure 23-21 shows how a self-resonant coil can replace a
short-circuited 1/4-wave stub in a phase-reversing trap. If you don`t
have the 3rd edition of "Antennas", get it.

Cecil wrote: "I am not asking for fiber optic measurements."

Very likely they aren`t necessary. I`ve measured currents along antennas
draging a sampling loop along them with a rope. A transit determined the
position and its telescope made the r-f ammeter in the loop readable.

Surely a loop and its ammeter can be small enough not to upset the
measurements if you use enough power and have a low enough frequency. As
Richard Clark might say: "We don`t need no stinkin` fiber optics."

Best regards, Richard Harrison, KB5WZI

 
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