> > > It's hard to answer your question optimally without addition
> > > information.
> > >
> > > 1) What's the frequency of the tone?
> >
> > Variable.  I  am using the circuit to decode cw and would like to
> be able
> > to vary the tone.
> >
> > > 2) What's the amplitude?
> >
> > A nice sinewave.
>
> Nice 1mV sine wave or nice 100V sine wave?

About ~1.2V.  It IS controllable by the radio its hooked up to.

> >
> > > 3) Is there any additional signal present along with the tone?
> >
> > static...
> >
>
> Spehro's circuit, or a variation there of, sounds like the ideal
> solution. His
> circuit is essentially a high pass filter followed by an amplifier.
> As it
> stands, the circuit requires a minimum amount of voltage to excite
> it, but
> grounding the emitter gives it really high gain. This is good and
> bad. It's good
> in that it thresholds your signal. In other words, the 'static' to
> which you
> allude would have to be very large (one good vague adjective
> deserves
> another) to trigger the signal.

Easy to get alot of static.  Find a weak (probably distant or very close)
signal and you want to work the station.

> It's bad if the "nice sinewave" is
> too
> small. Another minor problem is that Spehro's circuit's
> threshold/sensitivity
> has a strong temperature bias - but this IS a minor issue. Some of
> these effects
> can be mitigated by biasing the transistor. However, if you add an
> emitter
> resistor then the minimum drive level of the transistor will be
> affected.

I was looking for a IC solution.

> Scott

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