[time-nuts] Opera coordinator has resigned

[Jim Lux]

On 4/1/12 3:01 AM, Dr. David Kirkby wrote:
> On 03/31/12 09:38 PM, Jim Lux wrote:
>> On 3/31/12 1:15 PM, Brooke Clarke wrote:
>>> Hi Achim:
>>>
>>> SMA RF connectors have a very limited life (number of matings) until
>>> they are worn out.
>>
>> I don't think so. Yes, they're only rated for 500 cycles, but there's a
>> paper by a guy at Maury Microwave that I ran across when trying to get
>> statistics on the reflection coefficient variation, and he set up a
>> automated rig to mate/demate SMAs something like 10,000 times.
>
> I suspect that the jig he built does a better job of aligning them than
> what humans do. We put them on not quite square, move them around until
> the thread mates etc. I wonder if his jig tried to replicate a human or
> not?

Nope.. back and forth in a straight line.  He was measuring repeatability.


>
>> I suspect that there is a WIDE variation among mfrs in terms of life
>> performance and manufacturing precision.
>
> Yes, I've worked in places where they use the cheapest they can get, and
> others where the more expensive, but much better quality Huber and
> Shuner connectors are used. I would expect the more expensive ones,
> which are machined more accurately, would last for more
>
> There is also a relationship between the torque you tighten them and
> their life.
>
> I happen to work somewhere where I can't get my boss to buy a torque
> wrench for them, despite we use a lot of SMA connectors. I don't know
> how common that practice is. Everywhere else I have worked does use a
> torque wrench.
>
> I one tried a quick experiment tightening them up by hand as tight as
> possible, then seeing how many extra turns it required to torque them to
> whatever the torque wrench was set to (not all SMA torque wrenches are
> set to the same figure). As far as I can tell, there is no way of even
> roughly estimating how tight they should be by saying "hand tight + x
> turns".

Yes.. if you're talking about finger tight, there's a lot of 
variability.  With an inexpensive open end wrench, though you can get 
pretty consistent.. perhaps it's the "Calibrated thumb" on the little 
wrench?

Not anywhere as good as the "click" on the real torque wrench.