Mike,

I have seen people use 'series' and 'parallel' resonating when talking

about

loops, but what is the difference - surely if it is a continuous loop they
are both the same? Can someone clarify, please.

The difference is in the coupling method. The "series" version uses a
step-down transformer between the transmission line and the loop, with the
low-impedance secondary wired in series with the loop and tuning capacitor.
The "parallel" version uses a step-up transformer, with the high-impedance
secondary placed across the tuning capacitor.

The performance of the antenna should be the same in either case.

John Andrews, W1TAG