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#11
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folding a dipole in half
If you are having trouble with neighbours, then make a wooden antenna
using brush-handles, or even a fishing pole. Let the neighbours see it and make a fool of themselves when they accuse you of disturbance to the TV sets. Then you can use the real antenna another day without fear. ;-) Or get a Ham buddy to make a QSO on your station while you are over at the neighbors! "How can it be my station when I'm standing here in front of you?? hehe Must remember that one :-) Thanks! |
#12
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folding a dipole in half
Roy Lewallen wrote:
"Thus we see that the (quarter wavelength) folded dipole exhibits the qualities of a shunt-tuned circuit and has a terminal resistance value Ra of high magnitude." Yes, my copy of Bailey says the same. I got the 6000 ohms from page 509 in the catalog section where large diameter rods were used for the 200 MHz antenna. Looking at Bailey`s page 508, Fig. 8-14, it seems a 1/2-wavelength perimeter can be opened into a loop instead of a folded dipole and iits radiation resistannce drops to about 5 ohms. This is a mixed blessing because as Roy says, "There`s no free lunch". A loop configuration does not lower the loss resistance in the conductor and this will extract a larger percentage of the energy fed to the conductor with a lower radiation resistance. A closed loop has an inductive reactance at frequencies below first resonance (when the wire perimeter is almost 1/2-wavelength). This reactance can be compensated with a simple low loss series capacitor. It is unfortunate to not have room for a straight radiator. Best regards, Richard Harrison, KB5WZI |
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