GPRS shield turns off on incoming call

I’m using GPRS shield v1.2 mounted to Arduino Mega 1280.
I’ve loaded the test program (to use HyperTerminal for sending commands from PC) to Arduino and tested it.
It works fine (I’ve sent “AT” and received “OK”). Status and Netlight leds are on. Netlight blinks 64ms On/3000ms Off.

After that I’ve tried to call to phone number of SIM card installed to GPRS shield.
In this case - GPRS shield turns off immediately. Status and Netlight leds switches off.
The SIM card I use is from my personal phone and it works fine. Arduino Mega connected to PC through the USB cable and powers from it.

Could you please tell me what could be the root of problem?

Problem solved. The cause is bad powering via USB cable. Arduino should be powered by adapter


The problem is your power source, it cannot supply enough juice for GPRS shield, which might require up to 2A current peaks. USB usually gives about 500mA.

If you have a USB cable, that is sometimes supplied with portable hard drives and has two USB connectors, you might try that. Otherwise I suggest a separate power source for GPRS shield, giving at least 5V and able to supply enough current. Four AA’s would work (five, if rechargeable batteries). Or two 3.7 Li-Ion in series (7.4V).