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SWR goes very high as soon as the VFO is tuned to 14.255 after relay "clicks" in?

Rapidrob Member ✭✭

My 6400M last night made an internal sound I've not heard before when transmitting above 14.255.00. The SWR goes off of the scale. If I tune to 14.254.900 the SWR is less than 1:1.2.

I did a Truth-Table for 20 meters from one end of the band to the 14.350 Interlock and here is what I see:

14/150-14.234.950 : SWR 1:1.2

14.235-14.244.950: SWR is so high it is off of the scale a relay can be heard ..greater than 1:3.0

14.235-14.244.950: SWR 1:1.2 relay heard

14.255-14.274.950: SWR off the scale again, relay heard

14.275-14.294.950: SWR 1:1.4 relay heard

14.295-14.304.950: SWR off the scale again, relay heard

14.305-14.314.950: SWR 1:1.6 relay heard

14.315-14.334.950: SWR off the scale again relay heard

14.335-14344.950: SWR 1:1.7 relay heard

14.345-14.347 : SWR 1:2.5 Interlock kicked in. No higher Freq allowed as expected.

Something in the radio has failed? My other ICOM radio has no issues at any 20 meter freq.

Pleas help / advise what to do?

Thank you.



  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Rob, do you have the internal ATU?

    If so, retune in the areas where the SWR jumps up.

  • Rapidrob
    Rapidrob Member ✭✭

    OK, I will try that, thanks.

  • Rapidrob
    Rapidrob Member ✭✭

    I re-tuned the radio this morning and the ATU did the trick. I going to guess the memory for the band tune was corrupted? Does this radio have a memory battery? I do not leave power on to this radio due to many brown outs here in NM.

    Thank you for the ATU re-tune idea, Len.

  • VE7ATJ_Don
    VE7ATJ_Don Member ✭✭✭

    Rob... If you haven't (and don't mind doing it), it might be time to have your ATU 'forget' all of its previous settings and start building a new set -- especially if you've changed the antenna setup in any significant way.

    I find it's a good thing to do every once in a while, just as part of routine maintenance.

    Anyway, to have the ATU reset to 'out of the box', right-click on the ATU button and select 'Clear ATU Memories'. Then, you have a clear slate. Just reset the ATU as you move up and down the band :-)

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Rob, sometimes a small segment of a band will just be missed when you do the initial tuning. Another thing that happens is you do a retune due to rain or snow and it leaves that segment "wrong" the next time you operate there in nice weather.

    A mistake I have made is connecting a dummy load in place of my antenna, then accidentally tuning it instead of bypassing. Now that little slice of band is mistuned when I reconnect the antenna.

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