[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies

Richard (Rick) Karlquist richard at karlquist.com
Fri Jun 2 01:01:48 EDT 2017

Direct multiplication to 9192 MHz isn't used
by any manufacturer of any atomic clock that I
know of, due to its well known disadvantages.
I can state for a fact that it was summarily
rejected by the designers of the 5060/5061
(Cutler, et al).  In the 5071, I (being the
RF designer) also summarily rejected it.
The architecture that is instead used is indeed
complex and expensive as you say.  It is


On 6/1/2017 7:04 PM, Donald E. Pauly wrote:
> https://www.febo.com/pipermail/time-nuts/2017-May/105566.html
> The lock system on the HP5071 is complex and expensive.  My plan to
> improve the HP5061B is to to use a pair of third overtone crystals
> running at 91.9 mc and 100 mc.  I have come up with the magic numbers
> to lock them together.  This eliminates all multipliers with the
> exception of the A4 board. The 12.61 mc synthesizer input presently
> wastes half the microwave power produced by the 90 mc input in the
> unused lower sideband. Therefore only half the 91.9 mc drive is
> required.
> Eight bit ECL dividers in one package are available to perform the
> necessary lock.  When multiplied by 100 to the cesium resonance line,
> the 91.9 mc frequency is a few cycles high so that C field currents
> are reasonable. With crystal cuts for zero temperature coefficient at
> 25°C, it is possible to get along without an oven.  Room temperature
> performance at 25°C±5°C is ±15·10^-9.  Oscillator warm up time would
> be measured in seconds.
> Square wave modulation of variable frequency and amplitude shows
> promise for reducing the noise effects of the beam tube.  You can
> smoothly change the lock time constant, deviation and frequency.  This
> would avoid the big disturbance of the HP5061B when you switch from
> OPR to LTC. (OPR=operate with 1 second time constant, LTC=operate with
> 100 second time constant)
> πθ°μΩω±√·Γλ
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