[SOLVED] sim908c auto power down problem

[Hazar Hantürk Nalbant]

hi everybody,

when i connect just ipex-sma cable (with gsm antenna or not. it doesnt matter) to gsm antenna connector of sim908c after a few seconds it powers down.

if i take out sim card when ipex-sma cable connected it works fine or if i insert sim card and take out ipex-sma cable it works fine. i can send at commands to module like reading sms etc.

i looked also the current that consumed. it is 1A when the module just powered on then it remains at 200mA after a few seconds it suddenly powers down.

i couldnt find the reason. is something wrong with the cable or sim card or any other connection or something else.. please help me..:???:

 

[Hazar Hantürk Nalbant]

additional information: gsm antenna connector and gnd pins of sim908 are short circuit. it that normal??

it is not the same for gps antenna connector. it is short circuit with gps_vant pin normally..

 

[Hazar Hantürk Nalbant]

it is normal that there is short circuit between vdd and gnd pins of gsm antenna connector bec' there is only an inductor between them. so the problem was about power supply.

at the begining i was working on breadboard. since i have worked on pcb, the problem doesnt exist anymore. i think the problem was about the distance between battery and vbat-gnd pins of module. on pcb they are so close.