[AMRadio] infinite impedance detector vs diode


John Coleman jc at pctechref.com
Thu Sep 4 20:47:33 EDT 2008


Yes I know what you mean about wheels turning, I should not be doing this
but it interests me so.  I never learned how to use the spice software and
some day I have to do it.  Yes the Hi Z detector would be an advantage I
would think but I have heard others say it makes the bandpass to narrow.  Go
figure!
73, and tnx fer all the info
John 

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Jim Tonne
Sent: Thursday, September 04, 2008 7:18 PM
To: Discussion of AM Radio in the Amateur Service
Subject: Re: [AMRadio] infinite impedance detector vs diode


John:

I am under the impression that the high input impedance 
of that AM demodulator is perhaps its most important
point.  The fact that it seems to buffer the output load
from the detection action seems nice to me.

I think it could be made temperature-stable rather
easily by adding a diode in series with that 6200 ohm
resistor from the base to ground.  Then change the
resistor.  Base idles about .67 volts above ground so as
to just barely turn on the transistor.

Oh yes - the URL for those that may have missed it:
http://tonnesoftware.com/appnotes/demodulator/diodedemod.html

Yes, it would be possible to do the same kind of look-see
on a product detector.  All it takes is time!  I have some 
other stuff that needs attention right now;  wheels are
squeaking.

- Jim Tonne   WB6BLD   TonneSoftware.com




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