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Old March 20th 04, 08:25 PM
Richard Harrison
 
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Art, KB9MZ wrote:
"Here he (Moxon) showed a combination loop dipole that could be used for
at least three bands. What was important to me was the importance of
coupling which brings up the issue that no where does it say that all
antennas must be based around wavelength and the accompanying series
circuit."

Just as surely, Moxon does not say that his loop and dipole antenna is
aperiodic.

Every piece of wire has a frequency of first resonance where its
distributed inductance and distributed capacitance have equal reactance
magnitudes. At this frequency, these reactances of opposite types
exactly cancel leaving only resistance to oppose antenna current.

Either side of resonance, antenna impedance rises sharply due to
reactance. Radiation resistance causes the Q to be low as compared to an
unloaded LC tuned circuit. An antenna may have a Q in the teens while an
unloaded LC circuit can have a Q in the hundreds.

Moxon may have assumed his readers understood such antennas as his were
resonant and sensitive to frequency (wavelength).

I don`t have Moxon`s diagram but from Art`s description of long ago, his
version conjoins loop and center-fed dipole rod. The feedline connects
directly to the loop or through a variable capacitor. In either case,
coupling seems complete to me.

I guess Moxon didn`t motorize the capacitance in his T / gamma matching
system, so Art patented it.

Best regards, Richard Harrison, KB5WZI

 
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