[QuadList] IVC and Pulse Interval Modulation for video recording--why didn't others use this technique

[Ted Langdell]

Following up on the Denon use of Quad and how I ran across that:   
Googling for information on Pulse Interval Modulation (PIM) and  
International Video Corp.'s use of the technique for recording video  
on its successful 1" helical recorders.

The technology is described in IVC 800 series manuals as :

"...wherein the interval of the wave generated by an oscillator is  
inversely porportional to the amplitude of the modulating waveform.  
Advantages of this method of modulation are improved signal-to-noise  
ratio, greater bandwidth and improved linearity."

And perhaps no patent licensing?

The demodulation process produces "a series of spikes at twice the  
frequency of the modulated signal. These spikes are used by  
demodulator Q11 to generate a sawtooth waveform whose average area is  
a linear function of the modulated wave."

"After passing through emitter follower Q12, the signal is passed to  
the averaging filter (L3, L4, L5 and associated capacitors) a low pass  
filter which removes all frequencies above approximately 5MHz."

"The resulting composite video signal is then equalized for optimum  
frequency response (C53 and R95) amplified by Q14, Q16 and Q 17 and  
passed to two emitter follower stages, one for black and white video  
output and the other to furnish the required drive to the color  
processor."

Did other video recorders use PIM to lay a signal onto tape?

Ted


Ted Langdell
Secretary

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