wrote in message
oups.com...

Frank Dresser wrote:

Am I reading the nifty formulae wrong? It looks to me like he's
deriving
the distortion of a diode detector from the modulation index only. My
sense
of these things says that a 50% modulated signal at a tenth of a volt is
going to have much more distortion than a 50% modulated signal at 10
volts.

Frank Dresser

Very few radios drive the detector with anything near 10V.
The R390 and R392 have the highest diode drive voltages I have
seen and I think they are less then about 3V.

The range is extreme, but not outlandish.


Most modern, IE "solid state", receivers I have measured have less
1V. All that I have seen that use discrete diode detectors as oppossed
to ICs, have farily high AF gain stages.

But I'd expect considerably less distortion at 3V rather than 1V.

And I'd also expect that no radio really uses a square law detector to
detect the audio. Real detectors try to linerize a diode's operation by
lightly loading the detector with a reletively high resistance and trying to
minimize operation in the diode's "square law" area. Both voltage and AC/DC
impedance are important considerations in determing diode audio detector
distortion.

I suspect the term "square law detector" is the same sort of term as "first
detector" -- what's now known as a mixer.

I know I've been tripped up by these archaic terms before.

Frank Dresser