NavList:

The box you describe may do the trick for lightning protection, especially if it isn't connected to earth and you already have lightning rods well connected to earth in the vicinity. By earth I mean a metal rod rammed into moist soil (on land), or a metal plate in direct contact with water (offshore).

 If it's radio interference you want to avoid, things are quite different; in that case the box must be connected to earth and the largest gap in the conductive surface can't exceed 1/10 wavelength (lambda) of the highest frequency you want to stop. Lambda (in meters) is 300/f, where f is frequency in MHz.

I learned this while working on ligtning and EMI protection systems for land and ship installations.

Regards,

Damian Lopez

45N 75W

On Tue, 22 Jan 2019 at 8:18 AM, Tony Oz

<NoReply_TonyOz@fer3.com> wrote:

Hello.

The New Year celebrations are (almost) over, cleaning my home up I noticed several cute tin boxes - potentially useful as Faraday cages.

How critical is it to provide a good-quality (low impedance) electrical contact between the box and the lid? The boxes I have look like that - lid's sitting place on the box is painted over. A cellphone goes off the net when put in the closed box, but is it enough to survive a near lighting strike (with a GPS receiver, a watch and a calculator)?

I'm looking to wash off the paint somehow leaving the tin intact (for corrosion protection).

Please comment.

Warm regards,

Tony

60°N 30°E