[time-nuts] HP 5316B External Reference

jimlux jimlux at earthlink.net
Mon Jul 13 16:32:47 UTC 2020


On 7/13/20 9:02 AM, Richard (Rick) Karlquist wrote:
> 
> 
> On 7/13/2020 6:26 AM, Wes wrote:
>> Hi Magnus,
>>
>> I did have the manual when I posed the original question but I had not 
>> delved into the cal procedure until you mentioned it.  It seems to be 
>> a bit complicated for what it does. I wonder how stable this is and 
>> how often might it need to be repeated. Why they didn't use the 
>> external reference more directly is a puzzle.
>>
>> I appreciate your time in looking into this.
>>
>> Regards,
>>
>> Wes
>>
>>
> 
> I don't know the specific engineer who designed this injection
> locking scheme, but IMHO it's a "too clever by half" sort of
> thing (and that's being charitable).  Unfortunately, I encountered many 
> examples of that in the 5334A, and other counters.  I took out around
> a dozen of these "clever" circuits in the process of replacing the
> 5334A with the 5334B.  The engineers involved were outside their
> lane as the saying goes; I actually talked to them about why they
> designed the circuit in that way.  Didn't have a valid reason IMHO.
> Just having been in that environment, I would be distrustful of the 5316 
> design for anything important application like time nuts work.
> Actually, I would be distrustful of any injection locking multiplier no 
> matter who designed it.  Unfortunately, you can't conclude that
> a design is good simply because it came out of HP.  In some ways,
> it was disillusioning to go to work for HP and see what is
> really going on.
> 

The same is true of NASA (and probably any big organization).

In most cases, there's not some rigorous process to choose the "best" 
design, often it's "the first design that works" that is selected.

Subsequent revisions will sometimes purge "clever but non-robust" 
solutions.  Technology advances will also make "couldn't work 10 years 
ago, but works now" changes, although there are plenty of examples which 
"let's do it that way, because if we change it, we have to spend time 
explaining why"





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