[time-nuts] Aside about Triangle Waveforms

[J. Forster]

It's the AN/APN-1 in the USAAC version. There is also a USN version with
slight differences.


-John

==============


> A widely used WW-II aircraft radio altimeter used a triangular waveform to
> FM modulate a 400 MHz oscillator, employing a mechanical variable
> capacitor
>  constructed similar to a permanent-magnet loudspeaker.  To get the
> capacitor's diaphragm to reverse accurately, at the positive peak of the
> trianglular waveform, required a sharp, negative-going impulse to be added
> to  the
> peak of the triangle, creating a sharp notch in the waveform about 30%
> deep.
>  This makes me wonder about the limitations of speaker cones  attempting
> to
> reproduce complex waveforms.  If they had overall  feedback for positional
> correction, the spectrum of the resulting driving  waveform might contain
> some pretty complex components.
>
> Bruce Hunter
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