Geeetech

hotkebab99 wrote: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.

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,

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.

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.

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.

Hi !

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

Thanks

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 !

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

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...

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