Reply To: ESP-01 disconnects in a metal cold storage cabinet, external antenna options

At -86 and below, the limit for ESP8266 is marginal, and the metal cabinet acts like a Faraday cage. The ESP-01 has a PCB antenna and no external antenna input. We had the same problem in our warehouse and solved it like this:We replaced the module with an ESP-07S or with the U.FL connector version of the ESP-12 (the ESP-07S has no PCB antenna, only U.FL, so there is no confusion). With an RP-SMA panel-type pigtail cable from the U.FL, we brought the antenna out through the top of the cabinet, and on the outside we fitted a small 3 dBi rod antenna. If you want to use an ESP32, the ESP32-WROOM-32U follows the same approach. The code does not change, only the pin definitions.Keep the cable short (20-30 cm), since a long thin coaxial cable causes losses at 2.4 GHz. Keep the antenna at least a few cm away from the metal surface of the cabinet, and keep it upright. For us, the signal went from -88 to -61.On the Hermetry side, also do this: check the Open after (seconds offline) value in the offline rule. The default is 600, but yours may have been set to something short like 60, so set it back to 600. Short disconnections will not open an alarm, and a device that really disconnects will still be caught within 10 minutes. Details: Offline alarmları. Also keep the keepalive in the 30-60 second range; the PubSubClient default is 15 seconds.