Bernard presented on small magnetic loop antennas at the June meeting. Bernard has been working on these for many years, and the main message was -They work very well but must be made very carefully and you need to accept a number of limitations.
The main limitation is the very small bandwidth, followed by the high level of care required in designing and making them. A key issue is loop resistance. Bernard makes his loops from 1 inch copper pipe and to reduce the resistance from the joins, uses 4 x 90 deg angles, carefully silver soldered. His loop is a square!
For receiving, people have had great success with multi turn wire loops and a capacitor. These are well described in SWL circles.
Proof that loops do work for HF transmission is that they are often seen in government and military use even today. The trick is that the units they have are very well made (the best materials are used) and the use of a spot frequency only.
Much of the data Bernard showed us is available at the ZL2WB web site.
Thank you to Bernard for the talk and demonstration.