With regard to the version you made - did you account for the loading
effect of the PVC when you measured and trimmed the length of your
radiator?


Hi Dave, I was just about to recommend the QST article, but you beat
me. A few comments on why his antenna did not perform: As you stated,
the PVC will change the input Z of the radiator. Just about anything
that is too close to the radiator will change things.
According to EZNEC, a 5/8 radiator with 1/4 radials 5 WL above ground
is 80-j300. As such, with a single series inductor matching section,
the best 50 ohm match is 1.6:1. This could get worse or better
depending on the antenna's environment. It will also change if you
slope the radials.
There is an article in the ARRL Antenna Compendium #1 pp.101 that
deals with 5/8 antennas. It basically explains why a 5/8, depending on
the application, is NOT the best performing radiator.
Gary N4AST