[time-nuts] What sort of oscillator is this?

Bob Camp kb8tq at n1k.org
Sun Dec 14 16:24:01 EST 2014


> On Dec 14, 2014, at 4:14 PM, Jim Lux <jimlux at earthlink.net> wrote:
> On 9/28/14, 7:55 AM, Richard Karlquist wrote:
>>> I find it odd that an instrument that probably cost $50,000 when new did
>>> not have a TCXO as standard,  and perhaps an oven as an option.

A *lot* of places that had this stuff ran it out of a frequency standard distribution system 100% of the time. If you saw “TCXO” in the specs, the first thing to do was call the HP sales guy and ask if you could get a discount on one that had a crystal instead….. 

>>> But I think HP did this sort of thing a lot. Something that would have
>>> cost
>>> very little to add, became an expensive option. In some cases these
>>> expensive options are nothing more than enabling a bit of software,
>>> although the R&D cost of the software is probably a lot more than the
>>> hardware cost of adding a better oscillator.
> There's also a difference between the "kind of oscillator" in the instrument.. Rick can probably tell us for sure, but I've heard it rumored that counters typically got an oscillator optimized for accuracy and low aging, but not necessarily so hot for phase noise, while synthesizers and spectrum analyzers would get a good phase noise oscillator, but maybe with more aging, figuring that the "cal lab" at the customer's facility would reset the frequency every year anyway.

HP bought a *lot* of oscillators on the open market from a wide range of suppliers. They very much customized the spec’s on these oscillators to match what they felt were the needs of the target market for this or that piece of gear. 

> I'm sure there's also some aspects of whether customers were more likely to have a house standard or leave the equipment powered on vs connected to power (so that a "standby mode" could keep the oscillator powered on).

Back in the 80’s the federal government / DOD in the US issues an edict that gear could not be on overnight . Oddly enough they were a pretty large customer for this sort of gear. That did indeed impact the specs on the oscillators. In some cases the practice flowed down to contractor sites. That just increased the size of the market with on/off cycles. 

> And that in turn was somewhat determined by whether the equipment was "portable" (has a handle, like a 8563 spectrum analyzer) or "rack/bench" (like a 8663 signal generator).  The portable units aren't going to be powered on all the time, so you want something that is "ready to go" within a short time after plugging it in.

Some of that gear got low powered OCXO’s Back in the days when manuals with schematics were common it was pretty easy to spot this sort of thing. 


>> I worked for the HP Santa Clara Division for 19 years.  The reason
>> why a customer would NOT want a precision oscillator in a high end
>> instrument would be that he was going to use a "house standard".
>> We of course made OCXO's at SCD and "sold" them to other HP divisions.
>> It would not be impossible for a division to use a TCXO, but it would
>> be out of character given that we transferred 10811's at "cost", which
>> was then about $400.
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