[time-nuts] Ultra low noise Pierce oscillator???

[Richard (Rick) Karlquist]

I would like to add some perspective to this discussion.
The 10811 oscillator simply uses a plain vanilla Pierce
circuit configured so that one terminal of the crystal
is at ground.  The base emitter capacitor is replaced
by a mode suppression network to force operation to the
correct overtone and mode (C as opposed to B).  It uses
a common (at the time) transistor, the 2N5179.  The AGC
varies the DC collector current in the transistor.
A zener diode of a type which is known to have low noise
is used to bias the varactor.  There is no magic here.

The results are that below 100 Hz, the noise is strictly
determined by the intrinsic crystal noise (yes, crystals
have their own noise).  Intrinsic crystal noise can be
measured with an HP3048 type phase noise system, if you
know what you are doing.

At 1 kHz and above, the noise is strictly determined by
the buffer amplifier following the oscillator circuit.
Read Rob Burgoon's patent to understand why his patented buffer
is the best that can be built (ie limited by physics).
The actual buffer used in the 10811 has some compromises
in it that increase the phase noise floor.  You can
easily get back to optimum performance by using a
string of common base amplifiers.

It is therefore puzzling to me that there is a search
for the holy grail low noise oscillator circuit.  What
is it that you do not like about the 10811 circuit?

Rick Karlquist N6RK