I think the critical factor in this discussion
is the proposal to make a 'valid' comparison between the existing and
additional short mast. To do this, in practice you will have to be using the
same ground plane, (I think you already suggested this) and this I believe
will prevent you from being sufficiently far away from the 300 footer
(regardless of its electrical condition, grounded, resonant or otherwise) to
prevent pattern distortion from mutual coupling effects.
Commercial antenna farms do have these
problems but as we all know, any antenna system is always a compromise.None
I think an experiment along the lines of
what you suggest is an excellent idea for just seeing what the results
are, but I think any suggestion of a 'valid' comparison would need to be
modified in accordance with prevailing experimental conditions.
Using other peoples antennas is always a
lot of fun anyway- just my luck that all those I have used so far have been
bowled over a few weeks after the event! I have to say that watching a 300
footer being dropped is quite an experience- they always seem a lot bigger
when thay are spread out along the ground!
In summary, go for