ML,
Any/every thing around an antenna is going to affect it's radiation
pattern to some extent, including feed lines. How much affect those
things have is the practical aspect of that. The 'classical'
radiation patterns, typically shown, are just that 'classical', best
case possibilities. The more 'mundane'(?) patterns are usually never
going to be the same, and in most cases, not really all that
important, sort of. It would be nice to be able to predict things by
using the 'classical' patterns, but just not a very practical thing to
count on. Depends a lot on which bands you're talking about too.
'Directional' is typically more important for the higher bands than
the lower ones, propagation and all that 'stuff'. Which isn't to say
that you shouldn't worry about it, just only to a 'practical' extent.
The easiest/hardest solution is to just move the thing till it's
'right' for you.
Yeah, I know, sort of a totally useless post, right? Oh well...
- 'Doc