> choke joint

Yes but not 1:1.4E6 attenuation in one step. They usually have several
impedance steps afair? In my non-extensive experience achieving >50 dB
attenuation of nearly anything in 'one step' is no go (assuming it is not
tuned). Untuned one-step attenuators seldom go beyond 30 dB assuming that
they are to be reproducible and untuned.

Even a simple cover joint with wire-clad gasket has two or three steps
(depending on how you count).

Apropos attenuation, any idea why a cellular phone works perfectly (S
meter at 3 of 5 ?!) in a 4 x 2 x 2 meter welded steel safe with the door
closed? Not all the seams are welded perfectly (this is not a submarine)
but there are not enough bare wires to conduct the cellular signal inside
at that level I think ?!

Peter

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