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Elecraft KX2 and KX3 users - beware of loose BNC

On a recent activation in the DM/BM area and after 100s of activations, I noticed the BNC connector on my KX3 had loosened itself causing intermittent high SWR. The nut (something close to 11mm) required two full turns to tighten it against the conductive pad inside the case. One of the plug in boards had to be removed to obtain access for the spanner.

73 Phil

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Phil, have you connected anything other than coax to that BNC??

Elliott, K6EL

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Hugh’s KX2 antenna socket was loose not long after he got his a few years ago.
And yes Its a bit of an operation to tighten it, old mate Gordon VK5GY did the job for us which involved pulling out some boards from memory. Hugh hardly uses his radio as we mostly use my kx3 on our tag team activations. My kx3 is now 10 year old no 0804 and still going strong touch wood. We normally use a run of RG174 on our rigs not transformers or other accessories etc. directly to the socket.
Keep up the good work.
Regards
Ian vk5cz …

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No Elliot, I only ever connected a BNC plug with coax or a small dummy load on rare occasions like when I have been programming the keyer. I don’t use the radio in my home shack, only on activations.

73 Phil

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Yes, someone else had reported this exact issue to me within the last week. I’ll need to take a look at mine to see if any tightening needs to happen.

Gus
W9SSN

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OK Ian and Gus. When this happened to me the other week I leant my battery against the BNC to get a bond between the socket and the case. Doing this got me by for around 10 activations before returning home. It’s worth checking tightness for sure.

73 Phil

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I had some problems with poor SWR stability and blamed the co-ax. Seems likely that it was the radio. Must check when I have time. The KX3 does not get out much now as I use the Discovery instead. Not as good in many respects but waterproofing (more-or-less) is a game changer.
73,
Rod

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As with all these things, check there are washers (spring and / or star) on the connector.

The reason they come loose is missing washers and repeated use of connector. The BNC uses an over centre effect when the lugs on the socket ride in the slot. I’ve seen BNC sockets wear quickly on many Yaesu radios, I think some of them where made from butter not metal and always tweak the BNC plug with a file to reduce the fastening torque needed.

Run a fine flat file over the area circled to reduce the fastening torque. Probably needs 10 or so gentle strokes to make all the difference.

bnc

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Just wondering if this issue with the KX3 bnc socket is it with aftermarket side panels and guard fitted or the original elecraft panels?
Thinking of purchasing some protection for my KX3 I got a bit concerned on my last outing in GI.

73
Graeme

My KX3 has side panels and the perspex cover.
The side panels I have slot around the bnc socket, so the bnc socket doesn’t need undoing to fit the side panels.
I would am glad I have the side panels and perspex cover as it affords physical protection of the KX3.

73’s
David

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I would apply a spring washer or maybe nut lock before tightening.

Ahoi
Pom

PS: I see you changed your avatar. I’m already missing the ‘spliff-rolling Phil’. :wink:

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Ahoi Pom

Never tried a spliff! The photo was actually me repairing a break in my wire dipole on CT/DL-013 last October, as witnessed by Paulo CT2IWW who took the photo. Full size here, I can see why you thought I was up to no good!

73 Phil

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Yeah, when clicking on the avatar it was clear that you’re fixing some broken wire and not ‘taking amateur radio to new highs’. :upside_down_face:

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Hi Graeme
I bought the KX3 secondhand with the side protection panels and perspex clip on cover already there. I don’t think they are Elecraft made. The side panel as photo shows is sculpted around the BNC socket, so it wouldn’t have been removed to fit the side plate. I could have used loctite but didn’t bother, I just tightened it up without even checking if there was any washer behind the nut.
73 Phil

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Ever since water droplet found its way between the perspex and the display, I have left my KX3 at home and use a Discovery TX-500 instead. There’s a nice 3D printed hard plastic cover and set of connector covers for it on Etsy.
Dust / splash-proof and much thinner. I don’t miss the built-in tuner as I mostly use resonant antennas on a summit unless I am experimenting and then take my T1.

As you mentioned, a game-changer indeed.
73, Robert

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