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Old January 5th 09, 02:58 AM posted to rec.radio.amateur.antenna
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Default The $1000 Power Measurement Challenge

Art wrote:
"-----i.e. his book called "Reflections" which is just a bunch of BS
with respect to what happens at the end of a fractional wave antenna."

Everyone should have access to the 3rd. edition of "Antennas" by Kraus,
Marthelka, and associates. It is a true treasure. On page 177 is found
Figure 6-7, Approximate natural-current distribution for thin, linear,
center-fed antennas of various lengths.`

In each case, at the open-circuit end current drops to near zero. No
surprise, as Terman says on page 866 of his 1955 opus:
"Under most circumstances the losses are sufficiently low and the ratio
of wire length to diameter sufficiently great so that to a first
approximation the current distribution can be taken as that for a line
with zero losses; it then has the characteristics discussed in Sec.
4-5."

Section 4-5 is titled: "The Effect of Attenuation on Voltage and Current
Distribution".

Point is that antennas share current distribution characteristics with
transmission lines, and Sec. 4-5 is in Terman`s Chapter 4 (Transmission
Lines). This chapter starts on page 82 of "Electronic And Radio
Engineering" from that wonderful year 1955. The transmission line
chapter shows in excellent detail how incident and reflected waves
combine, and the energy patterns produced on antennas as well as on
lines.

Walter Maxwell is in-step with Terman and Kraus.

Best regards, Richard Harrison, KB5WZI



 
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