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

Donald E. Pauly trojancowboy at gmail.com
Fri Jun 2 17:51:22 EDT 2017

# 2 is not true.  A cut has either two turning points or zero.  Where
both turning points exist there are two temperatures at which the
temperature coefficient of frequency is zero.  Cut 0 on figure 6 at
https://coloradocrystal.com/applications has no turnover point.  It is
neither fish nor fowl.  Cut 6 is the normal AT curve with extremes of
±16 ppm for -55° C thru +105° C.  All curves normally intersect at 25°
C rather than the 27° C shown.  25° C is half way between -55° C thru
+105° C.  Curve 6 is the Tchebychev polynomial y=4x^3-3x and curve 0
is y=4x^3.

Consider the standard AT cut which has turnover points at -15° C and
65° C.  The lower turnover would ordinarily not be used in ovens.  A
set point error of ±1° C in the upper turnover point at 65° C results
in a frequency error of +14.875·10^-9.  For cut 0, that same ±1° error
in room temperature results in a frequency error of  ±31.25·10^-12.
This is an improvement of 476 to 1.  You apparently have not thought
thru what improvements are possible with thermal coolers/heaters.
Among these is near instant warm up and greatly reduced power for
thermal management.


---------- Forwarded message ----------
From: Bob kb8tq <kb8tq at n1k.org>
Date: Fri, Jun 2, 2017 at 12:43 PM
Subject: Re: HP5061B Versus HP5071 Cesium Line Frequencies
To: "Donald E. Pauly" <trojancowboy at gmail.com>


Which statement is not true:

1) That there is a tolerance on the cut angle of a crystal?

2) That true zero temperature coefficient only happens at the turn?

3) That heater based controllers are impossible to build?


On Jun 2, 2017, at 3:40 PM, Donald E. Pauly <trojancowboy at gmail.com> wrote:

That is not true.  I say that thermal coolers have made ovens
obsolete.  A zero temperature coefficient at room temperature is
easier to hit than a zero temperature at the upper turnover point when
such a thing exists.  See
curve 0 in Figure 6 at https://coloradocrystal.com/applications/ .


On Friday, June 2, 2017, Bob kb8tq <kb8tq at n1k.org> wrote:
> 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

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