[time-nuts] Square to sine wave symmetrical conversion (part 2)

jerry shirᴀr radio.n9xr at gmail.com
Sun Jul 26 14:48:27 EDT 2015


Hi Bob,

Help me to understand your remarks.

A.  The oscillator stage has a limiter.  (Agreed.)
B.  ​You can *easily* get <-160 dbc/Hz with an oscillator that has
harmonics in the
-10 to -20 range?
C.  But we are not talking about the signal from the oscillator stage
itself?
D.  Tuned buffers can have these higher harmonics and all is well?
E.  Okay.  We are now talking about downstream harmonics and not the actual
oscillator stage harmonics?

Ideally the oscillator stage should have no tuned circuits so that the
feedback of this oscillator stage utilizes only the tuned circuit of the
high Q resonator.  Okay.  What frequency components should the hi Q
resonator exhibit?  Should it be rich in harmonics or should it be pretty
limited to one frequency represented by a sinewave?  Are we talking about
the harmonics at the output of the actual oscillator stage or after a few
buffer stages?

Help me out here.

Thanks,

Jerry N9XR


On Sun, Jul 26, 2015 at 8:44 AM, Bob Camp <kb8tq at n1k.org> wrote:

> Hi
>
> Ummm …. errr….
>
> The oscillator loop has a limiter in it or it’s not going to work very
> well.
> ​​
> You can *easily* get <-160 dbc/Hz with an oscillator that has harmonics in
> the
> -10 to -20 range. With some tweaking you can get into the 170’s.
>
> It’s not the limiting by it’s self, it’s *how* the limiting is achieved.
>
> In most cases the “oscillator output” you are looking at is not the signal
> from
> the oscillator stage it’s self. You are looking at a signal that has been
> through
> several (like tuned) buffers before you see it. The same narrow band tuned
> stages
> can be used to “clean up” harmonics on any signal. The old style rack mount
> OCXO’s did a *lot* of this.
>
> Bob
>


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