[Elecraft] KX3 2M module SMA connector loosening

[kstover at ac0h.net]

All,

SMA's are also supposed to be torqued to 9 lb./in.. They make break over open end torque wrenches to do just that 
They are spendy so unless your installing hundreds of the things I'd use a deep well socket and a thin combination wrench of appropriate size.
I haven't looked at the transverter install procedure but can’t imagine trying to get the connector tight with the radio full of "stuff".

R. Kevin Stover    AC0H

ARRL, FISTS, SKCC, NAQCC.
One of the guys that made sneakernet irrelevant, in my little corner of the world.
“If it doesn’t work the first time you push the button it won’t work the 20th…Just stop.”

-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of Clay Autery
Sent: Saturday, May 26, 2018 3:50 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] KX3 2M module SMA connector loosening

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
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