works great, thanks for all!
my config:
ARDUINO UNO R3 + ICOMSAT 1.1 + ARDUINO IDE 1.X + LIBRARY FROM GitHub - jgarland79/GSM_Shield: GSM Library for the SIM900 chip and the GBoard Arduino GSM development board
*SWITCH ON "UART PORT"
*JUMPERS ON POSITION 2 (TXD -> UP) & 3 (RXD -> DOWN)
*OPTIONS FROM GSM_Shield.cpp by Default (2,3)
*Turn on pressing the first button (SIM900-POWER) after connect the arduino.
and works!!
my big question is: how i can put in "auto power-on"
thanks again.