[TowerTalk] Reliability (or not) of SMA connectors

[Richard (Rick) Karlquist]

Yes, properly torqued SMA's will not vibrate loose.
But if the items being connected are handled by the
operator or are just dangling, etc., then they can
conceivably come loose.  When I am doing R&D work
on my bench with a bunch of microwave tinker toys,
this regularly happens.  That is why I keep wrenches
handy while working.  Adding a component can cause
an existing component to loosen up.  For example,
I have a string of attenuators and I decide I need
another 3 dB, so I have to insert another one.
Then I have to recheck all the previous ones to
make sure they haven't loosened.  You must tighten
them with TWO wrenches at once, so that tightening
one doesn't loosen another.  No one mentioned that

I'll concur with the other comments that I have
never heard of gluing/locktiting etc. SMA connectors
at any company I have ever worked for.  These companies
all used LockTite on FASTENERS but not connectors.

Rick N6RK

On 12/5/2022 5:08 AM, Wes wrote:
> Same here.  I worked on Phoenix, AMRAAM, Standard and others.  We 
> torqued and were done with it. We used to shock and shake the bejesus 
> out of this hardware. Other things broke but I don't recall any 
> connectors coming undone.
> 
> Wes  N7WS
> 
> 
> On 12/4/2022 3:27 PM, Gary NA6O via TowerTalk wrote:
>> I’ve worked on dozens of different airborne and army ground-mobile RF 
>> assemblies over my career, as well as poking my nose inside many 
>> pieces of commercial RF gear. SMA connectors were everywhere. NEVER 
>> have I seen or heard of any kind of sealant, overcoat, or anything of 
>> the sort on any SMA connector. Above all, putting anything inside the 
>> threads is simply asking for trouble. TORQUE IT PROPERLY and be done 
>> with it. A quality SMA connector is a high-precision machined assembly 
>> and must be treated with care. See the old HP application note AN-326. 
>> They are in fact vibration-resistant when correctly installed. Proper 
>> torque is also mandatory to avoid well-known frequency response 
>> aberrations in the mid-GHz range due to waveguide effects.
>>
>> Of course, if your connectors are all crap and/or damaged, none of the 
>> above applies...
>>
>> Gary, NA6O
>> _______________________________________________
>>
>>
>>
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