KX3 6 meter VSWR issue.

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KX3 6 meter VSWR issue.


I'm having a problem with my KX3 that I have not been able to resolve.

KX3 S/N 7210, FW 02.25


While performing a tx gain calibration using the KX3 utility software (rev, it failed when trying to cal 52MHz.  This was because the VSWR on that band was 1.8:1 (dummy load directly connected - no cable, ATU bypassed).  I checked the load (Narda 40W D.C. -> 12GHz) and it checked OK using another rig (TS480) - flat across the (6M) band as you would expect.

I was orginally having issues when the voltage would drop below threshold causing the power level setting to change and that would result in no power out (PSK31).  TX gain cal fixed that on the problem band (40 meters) and 160->10M is fine.  Honestly, I don't think I ever tried 6 meters - no interest at the time - so this problem could have been there since day one - but the factory inspection test (the inital TX gain cal?) should have caught it, so not sure when or how this would have occured.

Thinking that perhaps this was a config bit gone astray, I loaded a config file from February (about 2 months after I got the radio).  Still had the 6M SWR issue, but the power level was working OK....apparently that got pooched some time after that config backup.  The config backup  I did just before the TX level cal restored the power level problem - so that is repeatable - and fixed. Backups are a wonderful thing.  The 6M VSWR problem appears to be unrelated - just surfaced during the TX gain cal.

If I enable the ATU, I can get a 1:1 match to the dummy load, and I get 10W out (KX3 meter). So...how to proceed? Seems like maybe a band switch/output tuning network problem?  Although, for 6M it is a straight thru connection (via K8).  

Comments appreciated.

On a positive note, great radio!...as I'm sure you have heard at least 7210 times;)  I'm am having alot of fun with this radio.  It's amazing what you can do on 40M with 3 watts and a dipole supended 10ft above salt water on a wood pier railing (long story) - 40dB C/N at 125Mi NVIS path.