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Problems in Frequency Selection

In Europe and Asia GSM networks are using the 900 MHz and 1800 MHz frequency bands. Whereas in Areas where the CDMA wireless network systems have been predominant the GSM networks have to use the 850 MHz and 1900 MHz frequency band. This areas are mainly USA, Canada, Central America and South America. The lower frequency of 850 MHz and 900 MHz is normally dominant in rural areas whereas in bigger Cities we will find either both frequencies or only the higher frequency. Basically we can split the world into this two GSM frequency groups. iMETOS is delivered present to the European frequency bands (900/1800 MHz). Otherwise it could not be tested in the Pessl Instruments GmbH workshop. If the iMETOS can not detect an network in this frequency band it changes to the 850/1900 MHz pair.
Reasons for problem in frequency selection: In some highly populated areas in South America (i.e. Santiago area in Chile) new local provider using the 900 MHz frequency band are occurring. This can prevent the iMETOS of selecting the correct frequency bundle. If the GSM signal at the site where you test the iMETOS is very very weak this can lead the iMETOS to the test of exotic combinations like 900/1900 MHz. Therefore make sure that you do not start the iMETOS in rooms where no GSM signal is available.
To prove if the reason that the iMETOS modem can not connect to the GSM network of which you entered the SIM card is the wrong frequency you will have to connect the modem to your PC by the use of the serial interface card for iMETOS. Please refer to Using the RS 232 Interface Card for Testing and Analysing the iMETOS. If the modem is connected to the PC and it responds on "at" by "OK" enter the"at+wmbs=?". This should be answered by "+WMBS: (0,1,2,3,4,5,6),(0-1)". If you are in America please enter now "at+wmbs=4,1". This will be answered by"OK". If you wait for a couple of seconds the modem will start to blink and if the 850/1900 MHz band combination is available the modem should connect to the GSM provider and it will start blinking short on long off.
If you disconnect the modem now from the PC (disconnect it physically or remove the jumper on the interface card) and you reset the iMETOS it should connect to the GSM network and the iMETOS should come to the second step in communication (on, on off- blinking). If all other settings like APN, Username and password are correct and the SIM card allows GPRS data transmission the iMETOS should connect to the web server now. What is indicated by the 3, and 4 blinks blinking code.

 


Created by system. Last Modification: Thursday 09 of February, 2012 12:34:34 GMT by Lena.