The TETRA pulse

O2 state that the structure of the TETRA signal ‘can be seen only when the signal is demodulated using very sensitive equipment’.

They might be right, but our bodies are equisitively sensitive, and we are picking it up even though we cannot see it!

The image below was kindly provided by Rod Burman, an Electronics Expert from the Isle of Wight.

It was captured on an ancient analogue storage oscilloscope using a simple voltage doubler detector.

The image shows a single TETRA frame. The three shorter bursts and the fourth longer burst (actually two short ones without a break) make up a ‘frame’. The frames are repeated at a rate of 17.64 times a second (marked by the two joined bursts). The shorter bursts occur at a frequency of 70.56 Hz.

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