On 4/2/2015 10:10 AM, amdx wrote:
I'm about to build this circuit to compare output from different
ferrite receive antennas. I will be using it with the the FET amplifier
referenced at the bottom of the page, so the input impedance is not a
concern. I'm mostly interested in the DC output to monitor signal
levels. AM band frequencies.

http://www.crystal-radio.eu/diodedet...dedetector.htm

Any fix for the sinewave distortion in the second and third scope traces.
Mikek

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If you look at the paragraph above Figure 8, the distortion you are
seeing is for a carrier frequency of 10 kHz. You shouldn't see a
problem at AM broadcast band frequencies.

And the others are right. You can limit distortion by increasing the
input voltage to the detector or decreasing the voltage required for the
rectifier to conduct. For instance, a germanium diode has a voltage
drop of around 0.3V, while a silicon diode has a drop of about 0.7V. A
precision rectifier, as Jan suggested, is even better, with a voltage
drop of near zero volts.

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