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I am using ESP8266 (2.4GHz wifi) in my product which has metallic enclosure on outside but only plastic on the other side. I will be placing this device outside home near gate. Will it be problematic for the wifi to be in metal enclosure. (Plastic side will be towards the router). Do i need to put window or will it work without window?

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  • \$\begingroup\$ What do you mean by the outside and the other side? If you have an enclosure that is metal in one direction and plastic in another, the plastic effectively is your window (however you still need to consider the proximity of the metal ground plane to the antenna). If you mean an enclosure that is metal covered or plated plastic in all directions, that's electrically a metal box... \$\endgroup\$ – Chris Stratton Aug 31 at 9:37
  • \$\begingroup\$ But take a step back; how are you going to power this? Wifi is a bad match for batteries, even if you only wake up in response to some event, you have to take time to register on the wifi network which may increase the response time. It can be done but it is probably not the best solution - either running signal back over wires that carry power out, or a simpler radio scheme that doesn't have a registration procedure is probably more suitable. Even using the raw radio frames mode of the ESP8266 without a wifi network would be preferable. \$\endgroup\$ – Chris Stratton Aug 31 at 9:39
  • \$\begingroup\$ Its a cuboid with six of front faces having plastic body over which there is metal enclosure (insulated paint). On the back side, there is only plastic and no metal. Back side will most of the time facing towards router. Size is 10 cm x 8 cm. \$\endgroup\$ – Akshit Aug 31 at 9:42
  • \$\begingroup\$ It is powered by smps power (5V) connected to LDO of 3.3 V. It is must to be a wifi and have IP address. Also sometimes used in AP mode (as gateway for settings). I do not have any ground plane on pcb below antenna of esp8266 but have ground place nearby at end of antenna. Will that be an issue? \$\endgroup\$ – Akshit Aug 31 at 9:45
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    \$\begingroup\$ Fixed? By who? Under what decision process? The ignorance of technical factors displayed in getting to the point where you are now is your real problem. It may work if the non-metallic face is enough of a window and the antenna far enough from the metallic faces, but you are in an unfortunate position as a result of poor decision process. \$\endgroup\$ – Chris Stratton Aug 31 at 9:54
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Generally, if your metal enclosure is grounded and thick enough, congratulations, you might have built a faraday cage and no RF enters or leaves.

In reality, the thing is probably not a perfect Faraday cage, and you're just greatly reducing the performance of your Wifi by abusing the enclosure as a very bad antenna element.

So, yes, a plastic window would sound wise.

Also note that unless you really seal the enclosure in a dry state, you might want to ensure that condensation doesn't happen on the electronics. That can be a hard problem for outdoor electronics, depending on the climate.

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  • \$\begingroup\$ There is metal body outside. Over which i have plastic... Behind plastic there will be pcb and behind that there will be plastic close ( without metal) metal is not grounded and insulation paint over it. \$\endgroup\$ – Akshit Aug 31 at 9:25
  • \$\begingroup\$ what matters is the metal. your plastic doesn't. \$\endgroup\$ – Marcus Müller Aug 31 at 10:45
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Read up on slot antenna's, and cut a hole in the conductive metal box of the appropriate size for the WiFi band of interest. (Hole can be weather sealed by something non-conductive and RF transparent).

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