Alan, the rhombic is a relatively inefficient antenna that 'may' give
you significant gain in point-to-point service, which is why it was
popular in the early days of commercial and governmental radio
services...
For ham radio it is less attractive due to the real estate it requres,
due to the cost of the poles (it usually needs to be supported at a
number of points along each leg to stop excessive whipping in the
wind)... Less attractive because it requires retuning of the matching
unit for small changes in frequency...Less attractive because it
confines your communications to a narrow angular beam...
Being a long ways from the other population centers of the world you
may be in a situation where you find it effective... Most of us
don't...

cheers denny / k8do