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Old June 16th 04, 09:03 PM
Richard Harrison
 
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Cecil, W5DXP wrote:
"Richard, I think you would be surprised if ypu measured RF current
through the short at the shorted end."

I expect high circulating current but without loss not much current is
required of the power source.

In his 1955 edition on page 106 Terman says:
"Thus, if the line is short-circuited at the load, then at frequencies
in the vicinity of a frequency for which the length is an odd number of
quarter wavelengths long, the impedance will be high and will vary with
frequency in the vicinity of resonance (i.e., frequency corresponding to
quarter wavelength) in exactly the same manner as does the impedance of
an ordinary parallel resonant circuit. It is therefore possible to
describe resonance on a transmission line in terms of impedance at
resonance and the equivalent Q of the resonance curve.

On page 107, Terman gives a 200 MHz example. 2-inch air-dielectric coax
is used for 1/4-wave short-circiuited stubs about 15 inches long. The
resonant impedance is more than 250,000 ohms with a Q of 3000.

How much current flows into an impedance of more than 1/4-million ohms?

Best regards, Richard Harrison, KB5WZI

 
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