On 16/02/2021 15:13, John Walliker wrote:
On Tuesday, 16 February 2021 at 14:33:01 UTC, Clive Page wrote:

I have been surprised several times in the last few years to see people making or receiving mobile calls while in a lift. I had assumed that the sheet metal on all 6 sides would form a fairly effective barrier to signals, but apparently not. Does anyone understand why?

The gaps between the metal panels act as slot antennas and re-radiate the signal very effectively.
To make a Faraday cage at mobile phone frequencies all the panels would need to be bonded
together every few cm.

FM radio works OK in lifts. Maybe lifts are made of cardboard like
caravans. There's no need for much metal apart from the floor and a
framework to hold it together.

--
Max Demian