The B version has a piece of mast below the main part of the
antenna. Is there much difference in performance between
the arx2b and the original arx2?

My understanding is that the lower section (with its radial stubs)
serves as a decoupling element, and greatly reduces the possibility of
RF current flow on the lower mast.

The original ARX2 seems to have a reputation for being somewhat
installation-sensitive. In some installations, enough RF can flow on
the mast and/or feedline to alter the antenna's radiation pattern...
the main lobe can "squint" away from the horizon and thus reduce the
useful gain of the antenna somewhat. In other installations (with
different mast and feedline lengths) this wasn't as much of a problem.

Adding the decoupling section to the design has (from what I've heard)
significantly reduced the problem, and allows the ARX2B to perform
more consistently than the ARX2 did.

Standard copper-pipe J-pole antennas (and similar designs) tend to
have the same issue - unless you decouple them from the mast and
feedline somehow (e.g. insulated mount, and a choke on the feedline)
their pattern can be installation-sensitive due to RF current flowing
where you don't want it.

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