http://cgi.ebay.com/ws/eBayISAPI.dll...30959 97&rd=1

He might be making the J-Pole one-wavelength long which would
indeed result in about 3 dB of gain but at a relatively useless
take-off-angle.

I suspect that he's comparing a standard half-wave-radiator J-pole to
a typical "ground plane" antenna (a quarter-wave monopole, with one
set of quarter-wave radials, possibly tilted downwards for an
impedance match).

The latter sort of antenna falls somewhat short of behaving like
a true infinite-ground-plane antenna, as the radials are neither
horizontal nor infinite in extent. If I recall correctly, the
radiation pattern will be tilted upwards from the horizon by
a significant amount.

The J-pole will be close to 0 dBd, while the "ground plane" will
probably fall a few dB short of that figure out at the horizon.

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