On a sunny day (Wed, 4 Dec 2019 19:04:53 -0000 (UTC)) it happened Andrew
Smallshaw  wrote in
:

>On 2019-11-28, Jan Panteltje  wrote:
>>
>> Nice PI4 box:
>>  https://www.ebay.com/itm/223705304329
>>
>> Perhaps RFI screening is better too in this box.
>>  http://panteltje.com/pub/metal_raspi_box_IXIMG_0251.JPG
>
>I've seen this case in the flesh somewhere in the last couple of
>weeks. Can't recall where but it may have been on display the last
>time I was at the CPC trade counter.  Looked like a nice case but
>wasn't too interested, still stuck with the 3 for the moment (NetBSD
>compatibility) so active cooling isn't a must have.
>
>As for RF screening I'd be surprised if it makes too much difference.
>At RF it would really need to be grounded to have much effect.

That is IMO a misunderstanding
I your microwave oven no longer screened if not grounded?
The essence of a metal screen around a RF source is that no RF can get out.
Same with a lightbulb in a metal box no light can get out,
light is also EM radiation, grounded or not :-)

I have just tested it with one of these:
 https://www.ebay.com/itm/283425162724
  very useful instrument to have,
Old plastic housing with a Raspi2 sets of alarm many inches away.
This metal housing with a Pi4 you need to hold the antenna almost against it,
some RF is leaking via the wires though, USB power and HDMI cables are hot.

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