I'd never assume the horizontal pattern was
completely isotropic,
because it has three radial elements - not (say) a solid disc - as a counterpoise.
If it was measurable, it ought to have three lobes; hopefully equal.
So, rotating the antenna (pause to roll eyes at rotating a vertical antenna
)
as little as 30° ought to run the complete gamut from peak to null.
It's also important to be a shrewd observer of the behavior of your local repeaters,
because both WB1GOF/R/2m/FM Westford and W1BIM/R/2m/FM Paxton (at least)
have had lids not merely kerchunking the machines,
but deliberately jamming
some but not
all of the users.
So if (for instance) the
very first test transmission on a machine seemed OK
(especially if it had been idle and you didn't have to break in to a round-robin for a test),
but the first QSO with a human didn't live up to those expectations -
for instance, if it seems as if the repeater can't hear you,
it could be someone sending a carrier at the repeater
via a narrow beam antenna; to desense the input via FM capture effect.
Shrewd not just because you want to diagnose problems correctly,
but because if you don't realize you're getting jammed,
and you
or your helpful monitoring station hem and haw
about the problem, it feeds the lid and means they'll stay on you.
Part of "never feed the jammer" means
you don't acknowledge the QRM in
any way.
If you think you're getting jammed,
and one side or the other of the QSO just can't copy the traffic,
then you have to just say, "oops, gotta go; 73's" and QSY or pull the plug.
If the other op is clueless,
their confusion feeds the jammer even if
you don't take the bait.
I have
definitely heard that happen.
And of course you can't tell the clueless helper,
"hey, someone's jamming me", because
that feeds the jammer.
I expect you two guys know the drill in theory way better than I do.
I'm just giving you a heads-up that you have to bring your A game
on 2m in Metro West.