[ARC5] A discussion on AGC.

[Ian Wilson]

A triode has enough nonlinearity to be able to demodulate AM. The various
flavours of triode detector are biased to choose a region of curvature that
provides reasonable detection efficiency versus distortion of the AM
envelope.

73, ian K3IMW

On Wed, May 10, 2017 at 9:11 AM, Kenneth G. Gordon <kgordon2006 at frontier.com
> wrote:

> On 9 May 2017 at 20:55, Dennis Monticelli wrote:
>
> > Turns out that in order to achieve the simple addition or subtraction of
> frequency it requires a
> > non-linearity in the device.
>
> Of course.
>
> > A product detector has no problem demodulating AM.  It behaves somewhat
> like a synchronous
> > detector in that the BFO is tuned to the carrier freq.  Works well if
> drift is not a big problem.
>
> I understand that method, the so-called "exalted carrier" method, but what
> I meant was that in
> the case of the simple single-triode product detector used, possibly
> invented, by Collins
> ("borrowed" by Heathkit) those demodulate AM just fine with the BFO turned
> OFF!
>
> I have suspected for a long time that when the BFO is turned off, those
> detectors actually
> work like the "infinite impedance" detector, but I have never investigated
> this beyond my
> suspicion.
>
> In my earlier investigations on product detectors, I also discovered a
> version of a single-triode
> product detector, different from the Collins one, invented by a German,
> which was specifically
> designed to correctly demodulate AM with the BFO off.
>
> Ken W7EKB
>
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