I read in sci.electronics.design that Jan-Martin Noeding, LA8AK
wrote (in
) about 'Need more details for mounting high-Q oscillator coils?', on
Wed, 11 Feb 2004:

A rule of thumb says that the screen around an oscillator coils could be
3 times the coil diameter, and Radiotron Designer's handbook, 3rd
edition, 1941 says that the screen should go at least one coil radius
above the coil. But how far from the chassis should the coil winding
start?

The 'at least one radius' thing applies at both ends. The magnetic field
of a solenoid is axially symmetrical.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk