On Sun, 2007-12-02 at 12:55 +0000, Philip Pemberton wrote:
> Peter Onion wrote:
> > I think any simple circuit like that is going to be problematical as it
> > has nothing in it to cope with the variations in amplitude of the
> > signal , afterall it is Amplitude Modulated !
> 
> Hm. The signal is fed into a 4007 inverter that's been biased into its linear 
> region. Then the signal is amplified again in the same way and fed into one 
> final stage of the 4007 which is wired as a normal inverter.

> There should be plenty of amplification there to pick out the carrier and 
> ignore the amplitude modulation. With 500mV out of the receiver (which is the 
> case for most of the UK) it'll clip nearly all the time...

But simple clipping will not "ignore the amplitude modulation" becasue
the time between the zero crossing of the carrier and the point at which
the clipping starts is still dependent on the ultimate ampltude of the
signal.  The slope of the signal through the zero crossing point is
dependent on the amplitde, so much so that i'm pretty sure that if you
measure the slope at the zero crossing you can actually recover the
modulation.

PeterO




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