Further to Walters e-mail:

Gamal says it all. It was impossible to keep the Decca coils tuned
accurately and maintain phase constancy without the copper screening.

There is a photo in the Low Frequency Handbook, page 13, that shows the
Decca loading coils and the walls of the ATU building, with Lech, G3KAU;
this gives some idea of the coil and building dimensions.

There were some aluminium boxes around the Decca site containing coils. I
always felt that the boxes were rather large for the size of the coils
inside them - now I know why

Regards,
Peter, G3LDO

<[email protected]>.