SIM900 Startup problem

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I have a SIM900 in an Arduino shield produced by seeedstudio.com. It is all communicating properly (I can pass and receive AT commands), but it does not seem to acquire a signal. When it start up it sends the following:

yyyyyyyy
RDY

+CFUN: 1

+CPIN: READY

+PACSP: 0

The NetLight is doing a medium blank (the 800ms one) that indicates no signal, but I have verified that there is signal and the SIM card is working with another phone at the same location. I am using a AT&T GoPhone SIM card which is unlocked. I am in the United States. If I send a AT+CBAND? I get:

+CBAND: GSM850_MODE,ALL_BAND

Is there something else that I need to set up or that I can check?

Any suggestions would be greatly appreciated.
 

hello .
pleas answer the question . this is my question too.

Thank you all.
 

Hi,

Try to issue the command AT+CREG? in order to know if the module is searching the network.

Also, it is necessary to set up the correct band for the module. Thry using AT+CBAND.
 

I know this is old but did anyone figure this out? I have the identical problem. I think it might be that the 3G sim cards are not supported. Any info would be great.
 

rclymer said:
I know this is old but did anyone figure this out? I have the identical problem. I think it might be that the 3G sim cards are not supported. Any info would be great.
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I have the same problem. Netlight is blinking in 800ms. If I check signal strength, I always get 0,0 value.
 

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