Mobitex, developed in the mid 80's in Sweden, is offered on over 30 networks worldwide. Mobitex services are generally used by law enforcement, firefighting, ambulance, energy and transportation organisations.
Mobitex is a packet switched data communication network. It uses GMSK modulation with a 8000 bit/s data rate. By using this spectrum efficient modulation scheme, the bandwith can be limited to about 12.5 kHz. In Europe, Mobitex can typically be found on frequencies between 400 and 450 MHz. In the USA, the 900 MHz band is used for Mobitex.
PDW can be used to decode Mobitex. To get the best results, a discriminator output is absolutely necessary. A 2 level interface or RS232 interface is recommended. However, by using your computer's sound card, reasonable results can be achieved. You find the settings for PDW here.
Demodulated Mobitex GMSK signal
The decoded messages contain raw 8-bits data. Most messages look like a random string. The data is not necessarily encrypted, but is sent efficiently as Mobitex is charged per byte. The end user application determines the meaning of the data; this can vary from user to user. Mobitex offers a transparent channel.EB90 17:07:26 28-09-07 CCCC 8000 OK ('(
EB90 17:07:30 28-09-07 CCCC 8000 OK ASS 1=fG02tj:'i
EB90 17:07:52 28-09-07 CCCC 8000 OK B+&(AB+&6 '@D03 B
Readable text like in paging networks is rare, or is 'hidden' between random looking characters.EB90 12:30:30 28-09-07 CCCC 8000 OK B/ASwB/6~DE0WATCH OUT!!! Speedtrap A16
direction dordrecht at the zwijndrecht junction
EB90 13:46:57 28-09-07 CCCC 8000 OK BHmG AqBHm6~^E02 message gms@#address:
3 streetname road@$municipality: anytown
@%3@&msg id: 66123@(coordinates x 98212
y 439210@"gms status 0@,back@q