locked Re: HF+ SMA nut warning!!!

Ian DXer

Thanks for the warning Leif,

Though I had one of SMA connector nuts become loose a couple of weeks ago & I just temporarily finger tightened it.
After immediately watching your video I thought I should tighten the SMA nuts with my wrench. I was surprised at the amount
of give they provided, which concerned (and worried) me as I recall the SMA connectors were soldered directly to the board, but I didn't over-tighten
for fear of encountering the problem you experienced.
After reading your warning this morning I looked inside my unit. Fortunately all okay <phew>.

But I really would not like to encounter the situation you experienced & attempt a repair with my ageing eyes & the PCB layout tolerances. 
Most PCBs like this are assembled by robots these days for good reason.

I think I'll invest in a torque wrench like the type Graham describes.

That said, a couple of months ago I purchased a couple of adaptor connectors to attach to the SMA's of the HF+ to reduce wear & reduce the possibility of
loosened SMA connectors on the HF+. Also I use a flylead attached the VHF connector adaptor of my HF+ to avoid the connect/disconnect wear possibility & prospect
of cycle of loosened SMA connectors.

Given your lab usage of the HF+ Leif, I could imagine there would be a high cycle of connect & disconnect of the SMA input connectors & if combined with weight of cables supporting
HF+ & movement of them etc, it's only natural to expect a higher than normal cycle of loosened connectors.
The heat/cooling cycle of the HF+ during use vs rest & difference in temperature coefficient of the aluminium case vs brass connectors (re thermal expansion differences) might so very slightly over time
contribute to loosened connectors (I've seen this after many years with inferior connectors on some comms equipment, resulting in intermittent issues).
Remember one of the elements of brass is copper, which is a relatively soft metal, so we are limited to the amount of force we can provide safely (same with aluminium).

Perhaps in a lab environment or situation where user has a high connect/disconnect cycle with the SMA antenna inputs one could consider a combination of or all the following:-
a) Adaptors, b) flyleads &/or c) enclosure for the HF+ draw the antenna outputs via short flyleads within enclosure out to external connectors on enclosure.
This last (c) methodology (whilst perhaps extreme) might provide greatly longevity of the product in an environment where unit is subjected to lots of movement/stress.
A cheaper an easier option to c) might be to mount the HF on a wooden board or thick plastic breadboard with brackets & attach short flyleads to SMA connectors & support the short flyleads via several cable clips.
This would relieve the stresses on the SMA connectors of the HF+.



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