Home |
Search |
Today's Posts |
#8
![]() |
|||
|
|||
![]()
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 |
Thread Tools | Search this Thread |
Display Modes | |
|
|
![]() |
||||
Thread | Forum | |||
Inverted ground plane antenna: compared with normal GP and low dipole. | Antenna | |||
Three short simple questions about antennas | Antenna | |||
Poor quality low + High TV channels? How much dB in Preamp? | Antenna | |||
QST Article: An Easy to Build, Dual-Band Collinear Antenna | Antenna |