[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies

[Donald E. Pauly]

https://www.febo.com/pipermail/time-nuts/2017-May/105566.html

A guy by the name of David W. Allan used direct multiplication to
build NBS-4 and NBS-5, see http://tf.nist.gov/general/pdf/65.pdf .  He
didn't see anything wrong with it.  He used a commercial frequency
standard modified from 5 mc to 5.006880 mc.  That in turn was
multiplied by 1836.  This was a multiplier chain of 2·2·3·3·3·17.
When multiplied to 9192 mc, this is 90 cycles low so the standard
would be forced high by 0.05 cps..  They measured the locked frequency
standard to determine the actual frequency of the cesium line.  I
propose NO multiplier chain.

What are the supposed problems in using a direct submultiple of the
cesium resonance?  It seems to me that all other techniques result in
more phase noise there.  I found the relationship 91.92631770
mc·(137,075/126,008)=99,999,999.98992 cps=100,000.000--0.01008 cps.
It is low by 0.1 ppb and therefore cannot be adjusted by C field
current.  The C field can only lower the frequency.  There is another
relationship that gives a higher frequency of a fraction of a part per
billion which is easily adjustable.  Perhaps HP was unaware that such
a frequency exists.

πθ°μΩω±√·Γλ
WB0KV


---------- Forwarded message ----------
From: Richard (Rick) Karlquist <richard at karlquist.com>
Date: Thu, Jun 1, 2017 at 10:01 PM
Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies
To: Discussion of precise time and frequency measurement
<time-nuts at febo.com>, "Donald E. Pauly" <trojancowboy at gmail.com>,
"rward0 at aol.com" <rward0 at aol.com>


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
also ACCURATE.

Rick


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
> WB0KV
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