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KX3 2M module SMA connector loosening

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KX3 2M module SMA connector loosening

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 with such a skinny nut in such close proximity to fragile components, and the thin lockwasher doesn't seem to be very effective. I thought I had cranked it down pretty tight, but apparently not tight enough.
I seems that it would have been better to have the separate nut on the outside end of the connector (like the connectors on the PX3), since those can be tightened up very easily from the outside.
One option might be to use Blue Loctite. I don't think I'd ever need to remove it unless Elecraft comes up with a dual-band (2M and 70CM) internal transverter to replace it, but this option would likely be permanent since I don't think I could get enough mechanical leverage to break the Loctite and don't think heating up the connector to loosen the Loctite would be a good idea.
Any better ideas?
Thanks and 73, Ryan AI6DO
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Mike Parkes

Re: KX3 2M module SMA connector loosening

Ryan,
I experienced the same issue on my kx3 also. I was able to tighten it down
enough with a wrench to keep it snug so far, but still keep an eye on it. I
also thought abt locktite but didn't like the idea of introducing non
conductive material between the case and the jack.
73's Mike AB7RU

On May 26, 2018 8:01 AM, "Ryan Noguchi via Elecraft" <
[hidden email]> 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 with such a
skinny nut in such close proximity to fragile components, and the thin
lockwasher doesn't seem to be very effective. I thought I had cranked it
down pretty tight, but apparently not tight enough.
I seems that it would have been better to have the separate nut on the
outside end of the connector (like the connectors on the PX3), since those
can be tightened up very easily from the outside.
One option might be to use Blue Loctite. I don't think I'd ever need to
remove it unless Elecraft comes up with a dual-band (2M and 70CM) internal
transverter to replace it, but this option would likely be permanent since
I don't think I could get enough mechanical leverage to break the Loctite
and don't think heating up the connector to loosen the Loctite would be a
good idea.
Any better ideas?
Thanks and 73, Ryan AI6DO
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Mike Parkes

Re: KX3 2M module SMA connector loosening

Ryan,
Another option is to use a short length of coax, sma male to sma female, to
avoid the issue of something torquing the SMA jack on the KX3 loose.
Something like this?

https://www.amazon.com/DHT-Electronics-coaxial-assembly-female/dp/B00COJWS32/ref=sr_1_5?ie=UTF8&qid=1527357956&sr=8-5&keywords=sma+male+to+sma+female+cable

On Sat, May 26, 2018 at 10:51 AM, Ryan Noguchi <[hidden email]> wrote:

> Thanks for your email, Mike.
>
> I was thinking of trying to keep the Loctite on just one side of the
> connector (leaving the other side with metal-to-metal contact) and possibly
> also shaving off some paint from the outside of the KX3 case to provide
> better contact on that side. I think I'll hold off on that thought for now,
> as I'm not sure that's such a great idea.
>
> I'll let you know if I get any ideas or offline suggestions.
>
> 73, Ryan AI6DO
>
>
> On Saturday, May 26, 2018, 9:36:26 AM PDT, Mike Parkes <[hidden email]>
> wrote:
>
>
> Ryan,
> I experienced the same issue on my kx3 also. I was able to tighten it down
> enough with a wrench to keep it snug so far, but still keep an eye on it. I
> also thought abt locktite but didn't like the idea of introducing non
> conductive material between the case and the jack.
> 73's Mike AB7RU
>
> On May 26, 2018 8:01 AM, "Ryan Noguchi via Elecraft" <
> [hidden email]> 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 with such a
> skinny nut in such close proximity to fragile components, and the thin
> lockwasher doesn't seem to be very effective. I thought I had cranked it
> down pretty tight, but apparently not tight enough.
> I seems that it would have been better to have the separate nut on the
> outside end of the connector (like the connectors on the PX3), since those
> can be tightened up very easily from the outside.
> One option might be to use Blue Loctite. I don't think I'd ever need to
> remove it unless Elecraft comes up with a dual-band (2M and 70CM) internal
> transverter to replace it, but this option would likely be permanent since
> I don't think I could get enough mechanical leverage to break the Loctite
> and don't think heating up the connector to loosen the Loctite would be a
> good idea.
> Any better ideas?
> Thanks and 73, Ryan AI6DO
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>
>
>

Elecraft mailing list

Re: KX3 2M module SMA connector loosening

I agree with Mike,

Because of Arrow-induced self-flagellation, I'm using a SMA to BNC cable when I do satellite work, with the adapter cable secured with a little homemade clamp at the knurled KX3 cabinet screw to keep stress and torque off the KX3 connector.

73 Scott ka9p

-----Original Message-----
From: Mike Parkes <[hidden email]>
To: Ryan Noguchi <[hidden email]>; elecraft <[hidden email]>
Sent: Sat, May 26, 2018 1:14 pm
Subject: Re: [Elecraft] KX3 2M module SMA connector loosening

Ryan,
Another option is to use a short length of coax, sma male to sma female, to
avoid the issue of something torquing the SMA jack on the KX3 loose.
Something like this?

https://www.amazon.com/DHT-Electronics-coaxial-assembly-female/dp/B00COJWS32/ref=sr_1_5?ie=UTF8&qid=1527357956&sr=8-5&keywords=sma+male+to+sma+female+cable

On Sat, May 26, 2018 at 10:51 AM, Ryan Noguchi <[hidden email]> wrote:

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Don Wilhelm

Re: KX3 2M module SMA connector loosening

In reply to this post by Elecraft mailing list

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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Clay Autery-2

Re: 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

kstover

Re: KX3 2M module SMA connector loosening

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: [hidden email] <[hidden email]> On Behalf Of Clay Autery
Sent: Saturday, May 26, 2018 3:50 PM
To: [hidden email]
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:

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Elecraft mailing list

Re: KX3 2M module SMA connector loosening

Yes, there is very limited space in that area so it's difficult to tighten that nut unless you have a very compact tool. My thinnest, smallest crescent spanner couldn't fit (much less turn) in that space, but rather than put the project on hold to find the right-sized tool, which in retrospect would have been the best course of action, I used a wrench to hold the outer (fixed) nut stationary while using the pliers to tighten the inner (free) nut. The Elecraft tech uses only a pair of needlenose pliers in their Youtube video that demonstrates their recommended installation procedure.

The multi-size spanner that KY5G suggested seems even larger, so likely would be too large to fit in that space. The problem is not so much thickness, but width. However, it is inexpensive and might be worth getting and trying. That torque wrench he suggested is probably small enough to fit and work, with its narrow "tuning fork" shape rather than a "crescent" shape, but at $115 is insanely expensive for something that I may only ever use again if I install a second transverter in my second KX3. I think what I'll do at this point is first see if I can find a suitable tool that isn't nearly that expensive.

BTW, I am using a coax jumper to reduce torque on the connector, but my application is pedestrian portable, not base-station or "picnic table" portable.

I appreciate the advice and the leads. I'll have to chew on this some before taking action.

Thanks and 73, Ryan AI6DO

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Petr, OK1RP/M0SIS

Re: KX3 2M module SMA connector loosening

In reply to this post by Elecraft mailing list

Dear Ryan,

in order to avoid the torqueing or breaking the SMA I can recommend to use
SMA coaxial jumper.
https://plus.google.com/100312042524727617304/posts/b4hvsciD3qG?hl=eng
...available on eBay, but be careful to get high quality only, PTFE
recommended.
Never use adapter or even set of few adapters directly.

73 - Petr, OK1RP

-----
http://ok1rp.blogspot.com
--
Sent from: http://elecraft.365791.n2.nabble.com/
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"Apple & Elecraft freak"
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