# [time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies

Donald E. Pauly trojancowboy at gmail.com
Sun Jun 4 00:56:51 EDT 2017

```You have a fundamental misunderstanding of the AT curve family.  See
my QBASIC plot at
http://gonascent.com/papers/hp/hp5061/photos/newxtl.jpg .  The
commonly described AT cut is shown as the largest sine wave in the
blue rectangle.  The left side of the rectangle is -55°C, the center
is 25° C and the right side is 105° C.  The bottom of the rectangle is
-16 ppm and the top is +16 ppm.

Main Cut
Temp   Freq
-55° C -16 ppm
-15° C +16 ppm
+25° C ±0 ppm
+65° C -16 ppm
105° C +16 ppm

You can get a lower turnover point of 24° C and an upper turnover
point of 26° C. Their amplitude would be °±0.250 ppb.  As the turnover
points approach each other, their amplitude approaches zero.  The line
joining all the turnover points is y= -8·x^3.  The zero temperature
for 25° is y=4·x^3.  Practical tolerance these days is on the order of
0.1 minutes of arc.  This is within the width of the traces in the
graph.

You are way off on your 0° to 50° C crystal.

["Umm …. errr … it’s quite easy to get a +/- 2 ppm 0-50C AT cut
*including* the tolerance on the cut angle."]

Temp   Freq
0° C   -0.488 ppb (lower limit)
12.5° C  +0.488 ppb (lower turning point)
25° C  ±0
37.5° C  -0.488 ppb (upper turning point)
50° C +0.488 ppb (upper limit)

As I claimed, a Thermal Electric Cooler has never been used to build a
crystal oscillator.  In the 50s, TEC efficiencies were on the order of
1% and were useless.  The Soviets made coolers more practical in the
70s with better materials.  I saw one used at Telemation that was able
to measure dew point by condensing water vapor on a mirror.  It looks
like efficiencies have now improved to 33% or so.

It was only in the early 70s that Analog Devices invented the AD590
solid state temperature sensor.  It made thermister bridges obsolete.
Switching amplifiers are required to drive thermal coolers if you want
to preserve efficiency.

πθ°μΩω±√·Γλ
WB0KVV

---------- Forwarded message ----------
From: Bob kb8tq <kb8tq at n1k.org>
Date: Fri, Jun 2, 2017 at 12:22 PM
Subject: Re: HP5061B Versus HP5071 Cesium Line Frequencies
To: "Donald E. Pauly" <trojancowboy at gmail.com>
Cc: "rward0 at aol.com" <rward0 at aol.com>, time-nuts <time-nuts at febo.com>

Hi

Any real crystal you buy will have a tolerance on the angle. In the
case of a crystal cut for turn the temperature will be a bit different
and you will match your oven to it. If you attempt a zero angle cut,
you will never really hit it and there is no way to compensate for the
problem.

Bob

On Jun 2, 2017, at 3:19 PM, Donald E. Pauly <trojancowboy at gmail.com> wrote:

A cut at that angle has no turn over temperature. The zero temperature
coefficient point is 25°.  Its temperature coefficient everywhere else
is positive.

On Friday, June 2, 2017, Bob kb8tq <kb8tq at n1k.org> wrote:
>
> Hi
>
> If you are going to use an oven, it’s better to run it at the turn temperature of
> the crystal. That would put you above 50C for an AT and a bit higher still for an SC.
>
> Bob
```