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

jimlux jimlux at earthlink.net
Fri Jun 2 19:02:40 EDT 2017

On 6/2/17 2:51 PM, Donald E. Pauly wrote:

> 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.

without getting into the whole crystal issue, one of the advantages of a 
heater is that it can be VERY simple (and hence reliable, just on a 
parts count basis). With a decent package, once it's hot, the power 
required to keep it hot can be quite low.

With a heat/cool, you need to be able to have a bipolar supply to the 
peltier device, and they're not particularly efficient (that is, to 
extract 1 Watt of heat, you're putting in significantly more than 1 watt 
of DC, and rejecting 1+X watts to the outside world.

And then, if you use a linear power supply/amplifier to drive the 
device, that is probably a class A device, and somewhat lossy.  A 
switcher would be more efficient, but then you have the problem of 
switching noise, in close proximity to the crystal. You could put a big 
low pass filter in, but now you're adding even more components.

There are undoubtedly some cases where the thermoelectric scheme would 
work better - for instance, you have a system with a TCXO and it's 
really set up for the TCXO to be at 25C, and you want to regulate that.

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