Sending data on a cellular network without connecting to the internet

I have been trying to send and receive data using a 2G cell phone network. I wish to communicate the bare minimum needed for telemetry and send waypoints to the uav. I hope that when i graduate to 3G, i can use a 3G video call for sending video and use the audio channel for telemetry,

These are my first attempts at this problem.

Got the following

1)2 sim900 modules for gsm communication

2)XR2206 for FSK

I realized that if i send a signal with frequency outside the 2-3.5KHz range, it gets severely attenuated. So i decided to use frequency shift keying to encapsulate the digital data into 2Khz for logic 1 and 3KHz for logic 1.

FSK seems to work well as seen on the oscilloscope. However when i send this signal from 1 GSM module to another, there is too much noise in the channel and i can't demodulate the signal using a PLL chip. There are even occasional random spikes that occur at around 10KHz.

Any thoughts?

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Replies to This Discussion

Permalink Reply by Jonathan T. Watters on July 14, 2012 at 12:51am

Reliable,  Long Range, Affordable, Safe  Let the GSM revolution begin!

Permalink Reply by Jake Stew on July 15, 2012 at 2:48pm

Unfortunately all cell phone tower antennas are directional panel/sectional type antennas and are pointed downwards.

YMMV because of this.  It's certainly not the best solution it seems at first glance.

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