[time-nuts] Cs tube pics

Tom Van Baak tvb at LeapSecond.com
Tue Nov 1 12:10:25 EDT 2016

> While I've no need for such accuracy in my little home workshop,  I
> *really* would like a Cs standard,  just because.
> The Rb and GPSDO are more than adequate for my needs but I can understand
> (and, for now, manage to resist) the addiction to accuracy and find it
> fascinating that such results can be achieved.

> I really would like to do that. But they are a tad bit expensive.
> Especially on this side of the big pond. If anyone is willing
> to part with a Cs standard and want to have it a good home, feel
> free to contact me :-)

It's true that a cheap GPS receiver is more accurate long-term than a surplus cesium standard, but you're right about the "just because" part. To me at least, this time nut hobby is not so much about the pursuit of accuracy as it is an appreciation for the variety, ingenuity and complexity of timekeeping. In some cases "how it works" is far more interesting that "does it work".

A used but known working cesium standard can be expensive, but like most of you almost all my gear comes from eBay via automated daily keyword searches. Many of my mil- or telecom-surplus FTS 4050 and HP 5061 were obtained for just a couple hundred dollars. You may search for months or even years, but amazing bargains show up. Not all of them work, of course, but the op/svc manuals are superb, the design / construction is very repair-friendly, and there's a weird group called time nuts with helpful advice.

Plus once you get more than one unit you can mix parts and create your own Frankenstein. It turns out that many surplus cesium standards are not dead due to tube failures so its a very happy day when a beat up 5061 turns out to have only a failed power supply or a bad OCXO yet the tube is in perfect condition. I remember one person picked up a "dead" FTS cesium standard only to find the reason it didn't work is that the switch on the back was in standby mode! Only one time nut I know ever bought a replacement Cs tube new from the factory. All the rest of us sift through the graveyard looking for the one that cries "I'm not dead yet".


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