Andy G4JNT wrote:

Aluminium kitchen foil is much thinner than the skin depth at these
frequencies, so you are getting nowhere near the full screening effect.

Many thanks for another clear description of what's actually
going on  - this time in relation to LF screening.  Another
precious Email, now added to my growing reference library  :-)

I'll repeat the tests with aluminium sheet - just as soon as I
find some - and report back with the results.

By the way, it was nice to work John G3CCH (RST 449) earlier
today - the first time I've heard him in several weeks.  PI4OSS
was 579 a few minutes ago - but no QSO was possible using my 12 m
vertical.

Regards to all,
Steve GW4ALG