[time-nuts] Just any counter external reference and discipline mode.

[Taka Kamiya]

I'm sorry to interject a newbie question....  I changed the title to distinguish from rest of the conversation.

I have heard this both ways about external references - whether it's used to phase lock internal source and used directly after some conditioning.  Both come from people on this list I trust.  Limiting discussion to HP counters from 70s to 90s, which is the truth?  Were there exceptions?  If so, why?  (I'm not interested in injection locking....)
If some are phase locking, what does it phase lock?  Most counters have options on internal reference (ie. HP53132A has standard, mid performance, high performance, and ultra performance)  Does it phase lock the standard that's always there?  Or try to phase lock optional reference?  I really don't see the need for phase locking, as only critical element is rise time - so rather, signal conditioning makes sense.  

At least for me, the general public, circuit diagram is not made available for later models.  I have no way to tell for sure what is being done inside.

--------------------------------------- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

    On Monday, July 13, 2020, 12:39:53 PM EDT, jimlux <jimlux at earthlink.net> wrote:  
 
 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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