I have a SIM808, connected via hardware serial to an Arduino Mega. Communication between the Arduino and the SIM808 is fine. However, the quality of the signal is listed as 0 all the time. (AT+CSQ)

I've checked, and there is definitely 2G (and 3G) signal. Power is fine. SIM is unlocked, and works in other M2M equipment.

The network status lights blink rapidly (ie searching for a network) for about 5 seconds. Then it takes one long blink, then goes back to blinking rapidly.

The module is picking up the names of the available networks, yet does not seem to be able to register.

I'm using a prepaid data SIM card from Vodacom (South Africa).

2 Answers 2


I think you are not giving it enough power, SIM800 module needs 5v/2A stable power source in order to register to network. Try to use a desktop computer power supply it has 5v/2A output wire (refer to colors).


Actually the SIM800 should not be supplied with more than 4.4 V according to the datasheet. I would be interested to know how this problem was resolved.

I have a similar problem. I cannot get the SIM800 to connect to Three or the O2 network even though both SIMs work in my mobile phone.

In my case the SIM800 is connected directly to two 18650 Li-Ion batteries in parallel so I don't think it is lack of power. Perhaps a big capacitor would help. I will give it a try. Failing that it might just have a much less adequate antenna and needs to be out in the open.

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