SIM900 - No registration to network

[Lemon]

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...

Dear friend,
I have sent the information and solutions to you via my personal e-mail.
Best regards.

[texouille]

Hi,


as far as i can see, not real solution was found for this module in order to work.

As you said onto your last post, you sent a workig solution,

can you share it with us?

Regards,

[hotkebab99]

Hello,
I have upgraded the firmware as you said to version 1137B03SIM900M64_ST_ENHANCE
. The firmware is upgraded but it doesn't work...
Here is the result of some AT commands :

AT

OK

AT+CSQ

+CSQ: 0,0
OK

AT+GSV

SIMCOM_Ltd
SIMCOM_SIM900
Revision:1137B03SIM900M64_ST_ENHANCE


AT+COPS=?

+COPS: ,,(0,1,4),(0,2)
OK

So the upgrade of the firmware doesn't solve the problem. The shield is not working.

[Lemon]

Dear All,
One of our customer shared his experience with the GSM/GPRS Shield on our forum, could you please see whether can solve your problems or not?

This is the link:
http://www.geeetech.com/forum/viewtopic.php?f=9&t=15861

Wish all of you a nice day.
Best regards.

[hotkebab99]

Hello,
My shield is working now !
The antenna connector was not soldered properly. I made some soldering work on my shield and it works now ! I am registered to the network and I can send/receive some SMS.
Here is the problem !
See the picture included in this message.

[kleofr]

Hi !

What exactly did you do to fix the problem? Am having the same problem.

Thanks

[hotkebab99]

Hi.
To solve the problem, I unsoldered on the antenna socket. Quite difficult but possible.
After, I soldered 2 wires : one on the SIM900 pin and the other on the PCB where the antenna was (on one side of the socket).
Next, I soldered these wire to the antenna cable : the SIM900 pin to the interior and the other to the exterior. Look at the picture just before !
I hope it will help you !

[kleofr]

Thank you,

After some research and an answer from simcom.... the IC that i have (sim900A) is locked to chinese networks only. That's why i cannot register to any EU network. I was told that i need the sim900 (quad) or the sim900R (dual).
Anyway, i ordered a different board with a "Quectel" IC

[Kralj1]

I have the same problem(no registration or very unstable with low signal) with some of my Geetech sim900 modules.... I did the same thing like hotkebab99 describes few posts back... success.... it is working now.... Looks like this module have some problems with antenna connector...

[briceagcosmin]

Hello everyone,

I've encountered the same problem as you .More exactly,I've designed a PCB for my diploma project which involves a GSM module . The design is according to the GSM datasheet. Besides the problem with the network registration, there is a short between the RF_ANT pin and the ground. Should be there such a situation?
I have to mention that the pcb was tested with the ERC rules . After that the manufacturer has tested too . So, I'm at a loss what to do. I've attached my project below in hope you understand more than I said.



Best Regards,
Bebe-Cosmin Briceag