For the longest time, I wondered why in the world anyone would use a folded dipole instead of a single wire dipole. Now I have my answer. :3
G8HQP wrote:
The increased bandwidth of a folded dipole is almost entirely due to the extra thickness. Two parallel elements behave as a thicker single element. There is a small contribution too from the combination of the reactances of the transmission-line mode and radiator-mode acting in opposite directions.
So that means my copper pipe dipole gets me the bandwidth advantage of a folded dipole, but can be fed with standard 50Ω coax.
I do understand the impedance matching quality, too. As in:
- A two-wire folded dipole has a 200–300Ω impedance, which means it can easily be fed with 300Ω twin lead.
- A three-wire folded dipole has a 450–700Ω impedance, which means it can be easily fed with 450Ω ladder line
If you want to feed either with coax, it's matching transformer time!
(I hope I didn't get things too wrong. :P)
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Neil E. Hodges
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