Well, if you look at the picture i posted, you will see
the 4 turns of 4" diameter loops that we placed in the RG-213,
just before the feedpoint.
Your site shows 10 turns of RG-58, which may or may not be
too many turns.
But barrel connectors have a bad reputation for higher losses
that if you used a mounted SO-239. For higher than 300 watts, you
should use a type "N" connector.