"Telamon" wrote in message
...

I don't anything wrong with what you wrote but you seem to think that
the diode used makes no difference because you can make it up its
deficiencies with an amplifier whose input impedance and gain adjusts
for it.

I don't think we disagree on anything important, but I wanted to say that,
after a point, it won't make any practical difference to the distortion of
the detector if a diode has a linear region or a very non linear square law
region. The resistance of the load soon dominates the characteristiscs of
the circuit.

The rest of my reply was mostly aimed at the original article's contention
that a diodes distortion level can be derived from only from a diode's
presumed square law characteristics and the modulation index.

Basically that is true that you can use a less efficient diode
but you will have to provide higher signal levels to it and weak
signals will still be distorted due to compression. I suppose you could
use a logarithmic type amplifier following the detector in order to make
up for the compression.

I suppose, but I don't see any need. The distortion of the diode detector
can be quite low if it's driven at a proper level to minimize the the amount
of the waveform in the non linear region of the detector.


If you look at the diode curves germanium has one of the better forward
current to input voltage ratios of several diode types.

Right. A germanium diode would generally give less distortion and better
sensitivity than a silicon diode. More than that, there used to be a bunch
of specialized germanium diodes intended for radio audio detection, video
detection and such. It seems now it's 1N34A types.


Not being a
radio designer my approach would be to use a diodes fairly liner region
with a better forward current to input voltage ratio where the least
distortion and compression would be due to it and therefor the least
needed correction to be made up for by a amplifier with a fixed
correction. Another reason to use a more efficient diode besides the
signal level power needed is the power the diode itself burns when you
bias the diodes with larger forward voltage junctions.


Efficiency is a bigger consideration with crystal sets.

Frank Dresser