[time-nuts] Divider circuit for Rubidium Standard

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Jan 11 00:52:56 UTC 2016

Anything like the pnp + diode circuit shown in HP application note 301-1?

    On Monday, 11 January 2016 8:00 AM, Richard (Rick) Karlquist <richard at karlquist.com> wrote:

 No, it was just word of mouth within the company.
Somewhere I have a piece of notebook paper
on which Tom drew the circuit.  We did have
internal forums where papers where presented,
but this was never even published internally.
As with all forums, a lot of stuff happens
outside the official forums in the hallways,
or over lunch, etc.  Ya gotta network.
There was probably a great sigh of relief when
I retired, and wouldn't be annoying coworkers
with endless questions any more.

Tom's contribution wasn't the circuit per se.
I used this same basic circuit at Zeta Labs
40 years ago.  I ever remember the PNP transistors
we used: the Fairchild 2N5771.  Those were the days...
Tom's contribution was pointing out the fact that it was
better than the other circuits out there,
and the fact that he gave a number.  It has
been a never ending battle to disabuse low
information designers of line receivers,
comparators, and other low performance solutions.

If you want to do some reading, I vaguely remember
that NIST published some papers on sine to square
at UFFC or PTTI.  Start with Fred Walls for your
search.  Also remember that this circuit, as good
as it is, is a poor mans substitute for the multistage
zero crossing detectors discussed on this forum many


On 1/10/2016 2:24 AM, Attila Kinali wrote:
> Hi Rick,
> On Sat, 9 Jan 2016 14:45:43 -0800
> "Richard (Rick) Karlquist" <richard at karlquist.com> wrote:
>> This circuit is very similar to one that was championed by Tom
>> Faulker of HP/Agilent at the now closed Spokane site.  Tom
>> measured the circuit at about -171 dBc/Hz.  He was very knowledgeable
>> about this topic, so we can believe the number.
> Is this documented anywhere publicly? I would be very interested
> to read this.
>             Attila Kinali
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