I'm doing a project using a SIM800L eBay module. I can send and receive SMS & calls.

The problem is that on the workbench it's working, but in an actual site environment, when the GSM signal is low, it disconnects and it won't connect to the network.

After I restart the module's power it works again and then it disconnects again. When I dial from my mobile to the GSM module it says "not reachable."

Is there any way to make the module ready all the time without disconnecting when in low-signal areas?

Power supply = 4 V/2 A.

On power up I only set the below AT commands:

  • ATE0 //echo off
  • CMGF=1 //SMS format text
  • AT+CNMI=1,2,0,0,0 //Command to receive live sms
  • Wait for button press to send SMS or wait for incoming call.

I use the spiral antenna which comes with the module.

  • \$\begingroup\$ I suggest you check your power supply with a multimeter. Please verify if it is really giving 4V,2A output. \$\endgroup\$
    – liaifat85
    Commented May 19, 2023 at 17:04

1 Answer 1


Try AT+CBAND="ALL_BAND". Try to sennd it after connection is established. The data sheet states that this setting is stored in the non-volatile memory but in my case it didn't so I made part of the connection script.


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