SIM900 - No registration to network

harry_chen · Post by **harry_chen** » Thu Feb 12, 2015 12:05 pm

Hi everyone
Sorry about the problem of the antenna connector.
It's possible the connector crashed in transportation.
Is it effective to clean the antenna connector and reconnect it, to make it tightly?
Geeetech has noticed it and we are improving our product quality all the time.
Thanks for your feedback!

to briceagcosmin:
The RF_ANT must be the signal ground, as a single-ended signal, and the other is the signal output.

Sincerely
Harry

briceagcosmin · Post by **briceagcosmin** » Thu Feb 12, 2015 3:17 pm

Hello,

Thanks for your reply.
Do you mean the RF_ANT pin must be bound to GND?If yes, what is the real signal?

Best Regards,
Bebe-Cosmin Briceag

harry_chen · Post by **harry_chen** » Thu Feb 12, 2015 5:59 pm

Hi
The signal inside and the ground outside, they measured short but actually not, i mean this.
Regards

briceagcosmin · Post by **briceagcosmin** » Thu Feb 12, 2015 6:32 pm

Hi,

I'm afraid I don't understand what you say.Are you talking about the antenna itself or about the connection between the sim900 module and the antenna?
So,this the schematic of the sim900 module:

.......1..2..3.....
| SIM900 |
| |
|..................|

Let's say this is the schematic, where: 1,3 means GND and 2 means the RF_ANT signal. The connection between the antenna and the sim900 module is according to datasheet.
My question is why there is a short between the 1,2 and 3 pin?

Best Regards,
Bebe-Cosmin Briceag

harry_chen · Post by **harry_chen** » Fri Feb 13, 2015 12:04 pm

Hi
OK, forget it.
Have asked the engineer,
There is a short as you measured, but only short in low frequency,
not short in some hign frequency
such as 850/900/1800/1900MHz, and it actually works in hign frequency.
The wire's width, length and position determine which high frequency can pass.
I hope it can help you.
Sincerely
Harry

briceagcosmin · Post by **briceagcosmin** » Fri Feb 13, 2015 3:25 pm

Hi,

Alright, thanks for your answer . I'll try to keep the trace as short as possible.

Have a nice day,

Best Regards,
Bebe-Cosmin Briceag

djekk · Post by **djekk** » Tue Mar 17, 2015 1:10 pm

Hi All,

I have sim900 board + uno r3

I made caller/dialer.

I met next situation:

my device lost network after night. Certainly I wrote source code, which reconnect if no connection with mobile network/

But

Why it is losing time by time ? how to check correctly or save my network connection?

zhangxueyou · Post by **zhangxueyou** » Wed Mar 18, 2015 4:01 pm

Sorry, djekk. We havn't met such an issue,neither can we find relevant information about it. I am sorry that we've tried our best but we can not find a solution.

djekk · Post by **djekk** » Wed Mar 18, 2015 4:15 pm

Hi zhangxueyou
do you have sourcecode for connection to mobile network by sim900?

zhangxueyou · Post by **zhangxueyou** » Wed Mar 18, 2015 4:54 pm

We only have sourcode of making a call and sending message, which you can find at this webpage:
http://www.geeetech.com/wiki/index.php/ ... PRS_Shield

Geeetech

SIM900 - No registration to network

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