Demodulating a laser beam O.T.
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Actually it is much simpler than that, a simple phototransistor well assume
npn with say a 1K from emitter to ground, and 10k from collector to a
regulated source, and a small cap from the collector to an audio amp.
In other words the vibration causes the reflection to move a small fraction
of a degree off center of the detector which causes a slight variation in
intensity. A.K.A. Amplitude Modulation.
KF4HAZ - Lonnie
Original Message
From: "John Fletcher" <g0roo@
> I haven't tried it but I would guess that you have to mix the reflected
> beam with a sample of the transmitter beam. The reflected beam would be
> phase modulated with respect to the transmitted beam.
>
> John
> --
> John Fletcher
npn with say a 1K from emitter to ground, and 10k from collector to a
regulated source, and a small cap from the collector to an audio amp.
In other words the vibration causes the reflection to move a small fraction
of a degree off center of the detector which causes a slight variation in
intensity. A.K.A. Amplitude Modulation.
KF4HAZ - Lonnie
Original Message
From: "John Fletcher" <g0roo@
> I haven't tried it but I would guess that you have to mix the reflected
> beam with a sample of the transmitter beam. The reflected beam would be
> phase modulated with respect to the transmitted beam.
>
> John
> --
> John Fletcher