[Antennas] Advice on mechanically 'tuning up' a Cushcraft R4 vertical

[Jim Shaw]

I have a old Cushcraft R4 (a multiband vertical 10/12/15/20) that has not
been used for 10 years even though I left it installed on the roof of house
(25 feet above ground at the base of the antenna).  When last used, the R4
was tuned so that the SWR was low enough to cover pretty much all four bands
without needing a tuner.  However, when I recently used it again, I noticed
that the SWR bandwidth was still OK for 10 & 12 meters but that it had
shifted down in frequency by about a half MHz on 15 (to about 20.5 MHz) and
on 20 (to about 13.5 MHz).

I am expecting to move in the next few months so I will be uninstalling the
R4.  While it is down, I am planning to try and "tune it up'.  I realize
everything from the coax feeding it, to the impedance matching box on the
antenna, to rust/corrosion of the main elements, to the traps in the antenna
could be a factor in its 'aging'.  And, even though I have other antennas
that I prefer, I want to get this one back in top shape again if that is
possible and reasonably inexpensive.

Does anyone have advice on what kinds of things to do to get the R4's SWR
back into the 15 and 20 meter bands. Are one or more of the traps the
problem?  Also, I would welcome any other advice on what to it mechanically
to ensure it will be "good as new" the next time it goes up.

73 de
Jim Shaw, WA6PXU
Jim@ShawResources.com
408-973-1608