[time-nuts] Divider circuit for Rubidium Standard

Attila Kinali attila at kinali.ch
Sat Jan 9 20:44:59 UTC 2016

Moin John,

Yes, I know I am comming back to an "old" discussion, but I have questions
that need to be answered! :-)

On Wed, 06 May 2015 08:56:10 -0400
John Ackermann N8UR <jra at febo.com> wrote:

> Wenzel has published the schematic of an excellent squaring circuit.  I 
> don't have the URL for their version handy, but I used it (with a couple 
> of mods) in the TADD-2 and TADD-2 Mini designs.  You can see the 
> schematic in the T2-Mini users guide at
> http://www.tapr.org/~n8ur/T2_Mini_Manual.pdf.

The manual says:
The purpose of the input circuit is to convert the RF input signal
into a low-jitter square wave that can drive the PIC clock input.
The circuit is closely based on the one published by Wenzel at 
http://www.wenzel.com/documents/waveform.html, with modifications
suggested by Bruce Griffiths and Ulrich Bangert. The revised circuit
works with inputs as low as -20dBm.

The modification I can see is that the "current source" part of the
differential pair changed from being a single, shared resistor of 100R to
an inductor of 100uH, then splits up into two resistors of 220R,
which are bridged by a 100nF capacitor. The inductor results in a
reactance between 62R (100kHz) and 12k (20MHz) for the input range.

Can you shed a bit of light on why you did those modifications 
and what the intended effect is?

			Attila Kinali

It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson

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