[TowerTalk] Folded dipole

[Martin Ewing]

The folded dipole will have wider bandwidth than a simple dipole,
because of the wire separation (and maybe other reasons).  The big
advantage in the old days (and now if you want it) is that the
impedance is transformed 4X.  A nominal 70-ohm free space dipole
becomes 280 ohms - a good match for 300 ohm twin-lead, which used to
be available abundantly for TV work.

You can get even higher transformations, by using 3 wires or more.
(And wider bandwidths, too.)

I think the main question is what kind of feed line do you want to
use.  Folded dipoles are at least a little better for open wire lines,
keeping the SWR down.

73 Martin AA6E

On Mon, Aug 24, 2009 at 10:22 PM, Tom Osborne<w7why at verizon.net> wrote:
> Hi All
>
> Looking to put up another 40 meter antenna.  Need a NVIS antenna for
> close-in work.
>
> Is there any reason to put up a folded dipole instead of a tuned-feeder
> dipole?
>
> I think when this antenna was popular, it was touted to have more bandwidth
> than a dipole.  But, if you have to use an antenna tuner to tune it anyway,
> there doesn't seem to be any advantage over a regular antenna, bandwidth
> wise.  73
> Tom W7WHY
>
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