jmorash wrote:
Thanks Roy! I think I understand baluns quite a bit better now. Seems
like, indeed, a couple ferrite beads could make quite a difference to
my radiation pattern.

This question is for Roy or anyone else who might know the answer: what
tool(s) do I want to try and gauge how good of an antenna I've built?
An SWR meter? Do they make those for 900 MHz? What else?

An SWR meter doesn't measure antenna goodness. The only thing it tells
you is how close the antenna's impedance is to 50 ohms, which has
nothing to do with the important measures of its performance such as
gain and pattern. The best test instrument is a low power transmitter
and field strength meter, one at each end of a simulated communication
link. For the other end of the link, it would be best to use a setup
typical of what you'll actually be using in the field. You'll be able to
get some idea of the antenna's effectiveness with over-ground tests, but
the ultimate test will be the strength of the signal received over water
with the antenna mounted as it will be for the real application. Precise
quantitative measurement isn't trivial at all, but qualitative relative
measurements are fairly easily made.

Roy Lewallen, W7EL