If a 2 meter J-pole construction is imperfect enough that
the short and long vertical portions are not exactly parallel
it might require an insulated piece of something to force them
to be parallel.

For what it's worth - the "American Legion" aluminum-rod J-poles which
are quite popular in my area have just this sort of separator near the
top of the matching section. It seems likely to me that the junctions
between the rods, and the aluminum crosspiece which forms the bottom
of the J-pole are not rigid enough to keep the rods parallel over the
lifetime of the antenna, and that bracing is necessary.

These J-poles use a somewhat uncommon feed technique - the SO-259 is
attached near the center of the crosspiece and grounded there, and the
short side of the matching section is fed through a bent-wire
transmission line and gamma match.

http://www.pcarc.net/jpole.pdf shows the construction, including the
crossbrace.

I'm not sure just what they use for the cross-brace - the document
indicates acrylic. This doesn't seem to stand up to sunlight all that
well in the long term - if I see an American Legion J-pole which has
failed, it's usually due to the cross-piece breaking. I'd suggest
ABS, black Delrin, or some other plastic which is more UV-stable (or,
just coat clear or white acrylic with paint to shield it from UV).

--
Dave Platt AE6EO
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