Fixing the Elecraft KX3 High SWR Issue 2

My KX3 Fully Loaded with ModulesA couple of months ago I installed the 2m Module into my Elecraft KX3 and after the install everything worked as expected, that was until I arrived at a SOTA summit only to find a really high SWR on all of the HF bands. On 40M the SWR was crazy at 99.9-1 and slightly better on 20M at only(!) 28:9-1…

Initially I suspected my linked dipole was at fault but after checking all the connections in the field, all seemed well. Without any other rig I resorted to using the ATU to resolve the high SWR, but despite getting a reasonable match and salvaging the activation all was clearly not right.

After getting home I checked the dipole over again, continuity checks confirmed everything was still connected where it should be. My antenna analyser also confirmed the dipole was resonant where it should be… queue some head scratching…

While installing the 2M module I remembered the mini coax cable had to be critically routed to avoid the toroids, the manual went to pains to state this:

2m Module cable routing

So having a spare hour on a Sunday evening I opened up the KX3 to see if this was the culprit and sure enough after removing the ATU and 2m module it was clear the cable was not where I originally left it:

The problem - Coax running over L42

The problem – Coax running over L42

As you can see the coax had shifted slightly and was running over L42, this certainly seemed like a feasible reason for a really high SWR. Moving the coax back to the right hand side of L42 showed that the cable didn’t want to stay put for long. I had thoughts of exactly the same issue coming back, especially after being carried up a few more SOTA summits.

A quick thought saw me using two pieces of Blu-Tack to try and secure the cable into position for a little longer:

Blu-Tack used to route coax correctly

Blu-Tack used to route coax correctly

Blu-Tack probably won’t keep it in place permanently, but should provide just enough encouragement to remain in place for longer. If the issue comes back I will try securing it in place with hot melt glue, but for now the issue has gone and SWR is back to normal:

SWR back to 1:3-1 on 40m with ATU bypassed

SWR back to 1:3-1 on 40m with ATU bypassed

 

SWR back to 1:7-1 on 20m with ATU bypassed

SWR back to 1:7-1 on 20m with ATU bypassed

If you’ve read this far you’ve probably have the same issue and if so I hope this fix also works for you!

The KX3 is now back in the game and ready for it’s next portable adventure on some god forsaken SOTA summit!

 

2 thoughts on “Fixing the Elecraft KX3 High SWR Issue

  1. Reply Dave Farrant (M6DFA) Oct 16,2015 10:47

    Thanks for that information. I will bear it in mind when I buy the 2m module for my KX3.

    • Reply James Stevens Oct 16,2015 13:42

      I hope it never happens to you Dave, but at least you will know what has caused it and how to fix it if it does 😉

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