Andy,
True, for the most part. But I was 'assuming' a center
fed doublet, not an off center fed one. (To cover all the
possibilities would mean more 'work' than I'm willing to
put into a 'simple' answer.) Both of us are 'right'.
'Doc

PS - I used an antenna something like what you described at
one time. Fed with ladder line through a tuner, it loaded
like a dream on all bands! Had a really 'crappy' pattern
for the use I wanted to put it (couldn't rearrange how it
was errected), so I went back to the 'loop'. Oh well...