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?
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".
Dave
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