[time-nuts] OCXO and fluctuations after EFC adjustment

[jimlux]

On 4/11/20 6:04 AM, Bob kb8tq wrote:
> Hi
> 
> Bottom line is that, as long as one is careful about *which* vendors supply which
> parts, normal parts do the job. Nobody is going to publish that selection process
> or the results. They very much want the “other guy” to have to do it on their own.

This is like low noise, low leakage FETs in high Z charge amplifiers - 
sure, it has a JEDEC 2N number and lots of people sell them, but the 
only ones worth buying are from that supplier in the UK, who "have the 
recipe".  And heavens forbid that they're sold or "lose the recipe".

(CSAC from Symmetricom vs Microsemi, comes to mind)



> 
> The 78L12 might look just like one from 5 other vendors. It also might work 10X
> better than the others. Those caps may look pretty normal. They came from
> “this guy” and not “those guys”. That cheap looking thermistor might have spent
> a few years in evaluation before it was approved for use.
> 
> There is a lot of work that goes into component selection. It simply does not
> result in $20 bulk metal film parts with 0.2 ppm/ C specs getting used. It is a
> lot more difficult to spot in the finished product.

And I suspect this is very much more so with "mass production" than 
one-off artisanal hand crafting. If you're building one or two or three, 
you can "hand select" or build 10 to yield 3 good ones.

This is the peril of "build to print" in the space business. The print 
describes the one you built in the lab, but there's no guarantee that 
the next 5 will perform the same.



> 
> Bob
>