[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies

jimlux jimlux at earthlink.net
Sat Jun 3 21:58:30 EDT 2017


On 6/3/17 5:54 PM, Bob kb8tq wrote:
> Hi
>
> The objective of the early work with coolers and OCXO’s was DOD sponsored. Low cost was
> not the goal :) The idea was that aging might be much better at the lower turn than at the upper turn. Once they
> played around a bit they found that activation energy was a real thing in this case. The improvement in aging
> did not justify the significant increase in complexity of the design. The idea has popped up about every ten
> years. Each time the conclusion after building a trial unit is pretty much the same.
>


I'm just picturing in my mind a 14 inch high rack mount unit with 
several hundred watts in heater power for the vacuum tube amplifiers, 
etc. needed to implement this kind of thing in the early 50s.

I'll bet someone also built one with mechanical refrigeration, a liquid 
cooling loop, and an electronic heater.  That one was a full rack 
cabinet<grin>

The "idea popping up every 10 years" is not restricted to crystal 
oscillators.  Anything where there's a "the technology doesn't support 
it" is the barrier. A couple generations and all of a sudden you can do 
it.  And sometimes it works - DDS and PN codes are examples of things 
which were barely feasible some decades ago, so people went through all 
sorts of gyrations to achieve goals with out it, but now, it's "oh yeah, 
sure, a parallel correlator to acquire and track 32 simultaneous GPS 
signals, isn't there an Arduino Sketch for that?"




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