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Old April 27th 04, 02:00 AM
The other John Smith
 
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"Richard Harrison" wrote in message
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Al, WA4GKO wrote:
"---when it`s too short for resonance, reactance is capacitive, and is
inductive if too long."

Thats exactly correct for an open circuit dipole or monopole, but folded
elements are backwards because they operate like loops and shorted
transmission lines.

Kraus says:
"Consider a two-wire folded dipole shown in Fig. 14-27a. The terminal
resistance is approximately 300 ohms. By modifying the dipole to the
general form shown in Fig. 14-27b, a wide range of terminal resistances
can be obtained, depending on the value of D. This arrangement is called
a T-match antenna."



On the page before that, page 417, Kraus also gives the impedance of the
folded dipole. He says it is 4 times the impedance of a two-wire dipole.
This means that, if the 2 wire dipole is capacitive slightly below
resonance, so is the terminal impedance of the folded dipole. Multiplying a
complex number by a real number does not change the sign of the imaginary
part.

John


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