Re: more on folded dipoles (long: delete now if not interested)

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From: cebik@UTKVX.UTCC.UTK.EDU
Date: Sat Dec 23 1995 - 05:31:29 EST


Paul,

Thank you for your observations and especially for the description of
your procedures in setting up a folded dipole for proper operation. Too
often, I (and possibly others) am tempted to "throw up an antenna"
without taking the time to ensure that all parts of the total
antenna-feedline-balun-matching system are operative and integrated.
Today, the tools for making the parts work exist and are accessible.

I appreciate your notes on using a 6:1 balun to match the nearly 300-ohm
FD Z to 50-ohm coax or 50-ohm rigs. A 4:1 balun will work with a
reasonably low SWR, but the 6:1 balun is more precise. Some of the folks
on this list may be interested in a construction description. Of course,
using 300-ohm line to an ATU or fixed network in the shack or at the
window sill will also work fine. Since this will be distributed, I shall
also add that whatever line is used for the FD elements (300-ohm,
450-ohm, home-made parallel line with spreaders), the feedpoint impedance
is 280-290 ohms, calling for 300-ohm feedline on the resonant frequency
for a proper antenna-to-feedline match.

Your note on some 300-ohm line being off the mark is also well taken. A
quality manufacturer like Belden or equivalent is wise--or check with
quality dealers like the Wireman or equivalent (with no specific
commercial recommendation intended here). There are some cheap, light
duty, no-name twinlead version available today that should be avoided.

Thanks again for putting the FD on a practical basis.

Happy holidays.

-73-
LB, W4RNL


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