SIM900 - No registration to network

[Lemon]

Dear friend,
I am sorry for my poor English.
We had already updated our information of GPRS. Could you please go to our wiki to find the Solutions for No Registration to Network?
This is the link to our wiki: http://www.geeetech.com/wiki/index.php/ ... PRS_Shield
Sorry for the inconvenience and your understanding is highly appreciated.
Best regards.

[texouille]

Hii Again

I read your new wiki entry.

Regards,

[ma.seguin]

Hi!

I have the same exact problem, but this is what I found:

After testing the conductivity of the antenna circuit, I found that the surface mount antenna connector was solder incorrectly. It was reversed and the ground was now linked to the sim900 antenna output pin. I soldered it back on the right side, but the damage were already made. Because it was soldered to the ground, the antenna output made a short-circuit and broke the sim900 antenna output.

Do you think you have the same problem?

[hotkebab99]

Hi,
After testing, as ma.seguin suggests, I found that there is a short-circuit between ground and the antenna pin of the SIM900 chip... On the AT1 connector, between the 2 pins of the connector, I have a value between 3 and 4 ohm. Not sure it is normal according to the schematics...

[hotkebab99]

After verfification, between the 2 pins of the AT1 connector, I have really a short-circuit (0 ohm)... strange. Isn't it ?

[Lemon]

Dear friend,
Sincerely sorry for the delay. We had a meeting to discuss your problem yesterday. My technical team are finding solutions.

Could you please restore the factory default settings first?
The code of AT command is AT&F0

After you restore the factory default settings, please test the signal strength of the module, and check whether the module can make gsm call or not.

Please have a try, after you finish tested, please tell me the details.

Waiting your reply. Best regards.

[hotkebab99]

Hello,
I will try what you say.
I have already try to do a factory reset of this chip whith the command you say. No result.
My question is to know if, according to what ma.seguin said, it is normal that between the two pins of the very small antenna connector located on the board (next to the SIM900 chip), there is a short-circuit (0 ohm). I think it is not normal for an antenna... Are you sure that it is not a soldering problem of the board ?

[KHeLiX]

Hi, I have the same problem with two of my boards, dead short between pin60 (RF_ANT) and GND.
No reseption, no registration.

[Lemon]

Hello,
I will try what you say.
I have already try to do a factory reset of this chip whith the command you say. No result.
My question is to know if, according to what ma.seguin said, it is normal that between the two pins of the very small antenna connector located on the board (next to the SIM900 chip), there is a short-circuit (0 ohm). I think it is not normal for an antenna... Are you sure that it is not a soldering problem of the board ?

Dear hotkebab99,
Thank you for your reply.
0 ohm is normal for the antenna.

Could you please try following steps:
1. Set the frequency band
The frequency band is usually set automatically, if you have changed the setting, you may not register to the network.
2. SIM900 support the frequency band of 900 or 1800
3. Read the frequency band first
AT+CBAND？
4. Check if the returned value conforms to that of SIM900. If not, set it as 900 to1800
AT+CBAND=”EGSM_DCS_MODE”

After you finished tested, please tell me the results.
Waiting your reply. Best regards.

[hotkebab99]

Hi,
First, not sure that 0ohm is normal for the antenna... How can it work if it is 0 ohm ?...

Second, concerning the frequency band, please read my first post, I have already tested what you say....

Here is another strange thing :
AT+CBAND?
+CBAND: INVALID_BAND_MODE,ALL_BAND

I think INVALID_BAND_MODE is not normal. I have tried to force the band with all possible values but the shiels doesn't connect to any network. More, everytime I start the shield, INVALID_BAND_MODE come back...

Thanks for your help even if I am not satisfied with the quality of this product...