In article ,
Walter Maxwell wrote:

For an EDZ in isolation (no mast) I believe it's around 3 dBd or 5
dBi, plus or minus a hair.

I modelled a copper-pipe EDZ, mounted at the top end of a conductive
mast. This one came out with 5.85 dBi in the favored direction, and a
2.5 dB front-to-back ratio.

Have I missed something here? As I understand the EDZ (is it not the Extended
Double Zepp?) it comprises a center-fed doublet with a 5/8 wl wire on each side
of the feed point. It's broadside gain is about 3.1 dBd, with a narrower lobe
than that of a dipole, from which the gain over a dipole is obtained. Am I
correct so far?

Yup.

If so, then we have only a single radiator. How then can there be a
front-to-back ratio?

The model I developed/posted was for an EDZ, which is side-mounted at
the top of a conductive mast. One half of the doublet sticks up above
the mast "in the clear", but the other half runs down parallel to the
mast, perhaps a foot away.

As with any side- or tower-mounted antenna, there's some amount of
reflection from the mast, and this is enough to create a few dB of
"front to back" ratio.

If the antenna were modelled (or used) in isolation, with no mast and
with the feedline running out sideways, the "front to back" ratio
would be unity or very close to it. Just delete the mast pipe from
the model I posted and re-run NEC.

The design/installation data for Telewave's side-mounted folded-dipole
arrays show several different patterns, ranging from something very
close to a cardioid, to an "off-center circular" pattern, to a nearly
perfect circular pattern. All of these patterns can be achieved using
the same antenna array, by simply altering the length of the
side-mount arms which support the dipoles beside the mast or tower.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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