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Old July 29th 05, 02:14 AM
John Smith
 
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Ham op:

Absolutely! Any amp is an oscillator, any oscillator is an amp... just depends
on how ya use it (mainly feedback.)

There is also the subjects of "thermal noise" and "quantum noise", both
contribute to the ease which with a circuit begins and sustains oscillations...

Well, unless the laws of physics have changed!

John

"Ham op" wrote in message
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John, I'm very serious when I say that 'white noise' is critical to
Colpitts/Hartley oscillator operation.

The feedback equation for oscillation requires a voltagecurrent gain greater
than 1 and a phase shift of 180 degrees [in simplified terms].

Starting conditions, in the absence of white noise, has zero input voltage
and hence zero output voltage and therefore no oscillation! The presence of
white noise provides the starting conditions, the Vin to be amplified, and
the tuned circuit, L and C, provides the frequency discrimination, and the
fundamental frequency of the oscillator. The Capacitive voltage divider
[Colpitts] or the Inductive voltage divider [Hartley] provides the feedback
factor. The active device, tube, transistor, FET, etc. provides the gain and
contributes to the phase shift.

White noise, frequency selectivity, gain greater than 1, and 180 degrees
phase shift are absolute requirements for an oscillator. In the absence of
any one there is NO oscillator. The white noise provides the starting
conditions for oscillation!!!

John Smith wrote:
Hmmm...

No, I don't believe I will have to read anything...

But, if you can't tell the difference between a white noise generator and an
osc giving a clean fundamental signal with greatly suppressed/filtered
harmonics (or even, non-existent harmonics), you may wish to read-up before
taking that project to the air...

John




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