Reg Edwards wrote:

It can now be seen why the conventional ATU cannot be used with
magloops. What is needed is something which searches for minimum loop
impedance, or zero phase angle, as the tuning capacitor is varied. It
then stops.

Any ideas?

There was an article in RadCom some years ago describing an auto-tuning
Top Band vertical, which used a simple inline phase detector and a
little DC tuning motor. The phase detector is nothing complicated - it's
very like a toroid-type SWR bridge rearranged components - but there
was a lot of practical information about what's necessary for RF
shielding and decoupling.

The whole thing should work equally well for a magloop, since the
electronics don't care what kind of antenna it actually is.

The article was by Tim Forrester, G4WIM, and was reprinted in G4LQI's
'HF Antenna Collection' book... my copy of which is unfortunately in
another country.


--
73 from Ian G/GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek