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Old July 9th 03, 05:43 PM
Clifton T. Sharp Jr.
 
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reach me through the sonic server wrote:
: Clifton T. Sharp Jr. wrote:
: (http://uweb.superlink.net/bhtongue/7diodeCv/7diodeCv.html).
:
: For RF diode detectors to work, one needs a device that has a
: non-linear V/I curve. In other words, the slope of the V/I curve
: must change as a function of applied Voltage.

: If there's any truth to this, someone please enlighten me. I've always
: been of the belief that an envelope detector diode would be most perfect
: if the diode was a perfect switch, i.e. zero attoamps reverse current
: and perfectly linear forward current (as though the diode was a wire
: during the forward conduction period). I don't see how a changing slope
: during forward conduction could do anything other than distort the
: demodulated waveform, especially on tiny signals.

Many detectors using diodes have an active bias voltage/current applied.
An Autek WM-1 peak reading watt meter is a great circuit of said.


And that removes a lot of the nonlinearity (especially by no longer
chopping the bottom 0.2V off the input signal). But this author seems to
be saying that detection can't work without that nonlinearity.

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