[Elecraft] KX3 2M module SMA connector loosening

[Clay Autery]

THIS!  There is no substitute for having the correct tools for the job!!

There are multi-size thin spanner wrenches made JUST for SMA and other 
small connectors...  Here is a link to the one that comes with my 
SDR-Kits DQ8SAQ VNWA:

https://www.sdr-kits.net/Flat%20Spanner

They sell it separately.  Of course, you could also buy a super 
expensive set of thin spanners...  <wink>

Additionally, as I study up on using my VNA, I have become more acutely 
aware that connectors have make/break cycle limits.   They DO wear out, 
especially if you over-torque them.  On PCB soldered connectors, it is a 
pain to replace them, so one might consider extending the lifespan by 
placing a sacrificial SMA Plug to SMA jack adapter in between the SMA 
jack on the radio and the feed-line....  IMHO, especially on portable 
radios/devices that are setup and taken down repeatedly, it is worth the 
additional insertion loss.  Just buy Amphenol or better quality ones and 
that is minimized.  Here's a link to a good one.

https://www.sdr-kits.net/sma-male-to-female

A good adapter will give you 500+ make/break cycles and still remain in 
spec.  Then, you just buy a new adapter rather than have to desolder and 
re-solder the PCB soldered, end-firing SMA jack.... assuming you can 
find the right one.
Thus the make/break cycle on your device only increments by 1 instead of 
500+.

Additionally, there IS a torque spec for SMA connectors...  It's about 4 
Lb-in for a brass connector, a little higher for stainless steel.  When 
mating stainless steel and brass fittings together, use the lower torque 
figure.  You CAN get fixed torque wrenches for connectors; they are not 
cheap.  I use my thin spanner or a flare fitting wrench and a Lyman 
trigger pull scale IF/WHEN I want an exact torque.  Main deal... don't 
over torque a connector.  I WOULD torque the adapter to the device jack 
using some method of measurement system.  Then, connect the feedline 
with the spanner...  The jack side of the adapter will spin on the 
rubber seal before reaching 4LB-in.... built-in over-torque protection.

Here's an example of an SMA torque wrench.... a very reasonably priced 
one all things considered:

https://www.sdr-kits.net/Torque-Wrench

73,

______________________
Clay Autery, KY5G
(318) 518-1389

On 05/26/18 15:16, Don Wilhelm wrote:
> Ryan,
>
> You need 2 wrenches (not pliers) - preferably thin ones.  Tighten the 
> nut down until the lockwashers bite into the KX3 enclosure metal so 
> the teeth have good conductivity to the enclosure.
>
> 73,
> Don W3FPR
>
> On 5/26/2018 11:01 AM, Ryan Noguchi via Elecraft wrote:
>> I recently bought and installed the KX3-2M transverter module in one 
>> of my KX3s and am enjoying a much better experience receiving the 
>> downlink from the Mode B AMSAT birds, compared to the TH-F6A I was 
>> using previously. Sensitivity and ergonomics are a huge improvement.
>> Unfortunately, I find that the SMA connector loosens very quickly. 
>> I've already had to open the case and almost completely uninstall the 
>> transverter once (undoing and redoing everything except the internal 
>> coax connections) just to retighten the nut, and it's already worked 
>> itself loose again. Does anyone have a trick they used to keep the 
>> nut from loosening? I can't get a lot of leverage with needlenose pliers