Tnx for the replies on this.

In the original post  I'd forgotton that Chu-Harrington described a
sphere just sufficient to enclose the antenna, so a pair od crossed
loops would fit into the same size as a single one, as Jim pointed
out.   The phasing issue should have been obvious too - as one writer
said, it is similar in outline to two crossed dipoles that just give
45 degree shifted linear polarisation if fed in phase.

Oh well, saves the effort of making one to test-out.   Back to writing software.

Andy G4JNT
www.scrbg.org/g4jnt