First aid for signal strength


1. Sim card pin


Suddenly the SMS Gateway stops sending text messages and does not receive a signal anymore. The configuration and the location of the SMS Gateway did not have changed. The common issue is a configured pin on the sim card.

To exclude possible issues with the pin you have to remove it from the sim card and the configuration of the SMS Gateway.



2. Reboot and powerless


If the SMS Gateway already have issues with the connectivity during the inital configuration you should halt the SMS Gateway and remove the power from it. This step should be done after a sim card switch or similar proceedures to exclude issues with already set data on the modem.



3. Location


The signal strength is correlated with the location of the SMS Gateway. If there is no signal the SMS Gateway can not connect to the mobile stations.


Factor possible issues
Antenna the used antenna can make a huge difference.
Cell tower blocked cell towers by the landscape.
Facility the signal strength in a room can differ a lot based on the walls.
Provider the signal strength can differ for a different provider.
Weather the weather can change the singal strength too.



4. Fluctuating signal


The modem of the SMS Gateway switches automatically between 3G and 4G. In some cases the switch can be an issue. Not every sim card is activated for 4G which will disturb the text message delivery. To determine if your sim card supports 4G you have to ask your provider.



5. Modem issues


To figure out if there are issues with the modem you can check the support lof of the SMS Gateway.


You can download the support log of your SMS Gateway in the web interface under Help - Support.

Open the received file with a archive tool. You can find the log of the modem under var/log/smsd.log.


You can open the file with notepad++ or similar.



The log can contain certain error messages:


Log entry Issue Solution
GSM0: CMD: AT+CPIN?: +CME ERROR: 10 (SIM not inserted) The sim card is not inserted or can not be regonized by the modem Insert a functioning sim card
GSM0: Couldn't open serial port /dev/gsm0, error: No such file or directory, waiting 30 sec.

During the initialisation the connection to the modem will be resetted. You can ignore this message if it shows only once.

If this message occurs more often there could be a issue with the connection between the modem and the SMS Gateway

For the Rack Editions you can check the modem LEDs: Modem Status

Otherwise contact our Support

GSM0: The modem answer was not OK: +CMS Error: 350 CMS Error 350 is a catch all error message which can have a lot of meanings The most common errors are listed here: CMS Error 350






Related articles