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"Interlock" Issues with FT8 on 60M

The first few night I tried operating FT8 on 60 meter channel 3 at 3.538 all worked fine. The next night, not the same. Now, anytime I try to transmit I get the "Interlock is preventing transmission". If I try transmitting in the the SSB or CW, 60M channels, all works fine, I don't get any Interlock msg.

Running a 6600 on Win10 and using WSJT-X v2.5.4. this combo is working fine on all bands other then 60M FT8. I have tried rebooting SSDR and the PC numerous times, to no avail. Can anyone offer any insight as to what may be occurring here and why the radio won't go to TX and why I am getting the " Interlock" msg??

73 Paul w2eck


  • bahillen
    bahillen Member ✭✭✭

    I had an issue with the 60 m interlock until I found I had to reduce the TX bandwidth in the rig applet to below 2900 hz.

    At 3kz the radio would transmit outside the permissible limits. Any other parameters that would allow the transmission outside the band allocation may also cause an interlock issue.




  • W2ECK
    W2ECK Member ✭✭


    What settings do you have for Lo and hi cut TXfilter?? I just tried 300 and 350 and still getting the InterLock msg

    thanks for reply

    73 Paul

  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator

    Are you using Fake It or Split in WSJT-X rig setup? On 60 meters this must be set to none.

    Dave wo2x

  • bahillen
    bahillen Member ✭✭✭

    My high cut is 2750 and low cut is 100. This maintains the maximum transmitted limits.

    My limit stops txing above 2950. Make sure your TX offsets are set to zero and the two buttons are greyed out.

    TX is 5.357 MHz

    you may try setting mode to SSB and see if it changes on FT8. When I can’t Tx the TX Tune button is greyed out. I think you can run FT8 in SSB MODE as a test if you meet TX in the area of 1500 hz. I have not tried this.

    I run DXU and RX bandwidth to 6 khz .

    Check what you have for region as the this may change the limits. It’s possible.

    If still having trouble try a help desk ticket.



  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    When you can't transmit on 60M is it because the radio thinks you are transmitting out of band. This is to make sure you are not making an illegal transmission.

    The common causes are:

    • wrong VFO center frequency
    • LPF is set too high (above 2800Hz)
    • Fake it is turned on in WSJT causing the VFO to change frequency and moving you out of the Transmit passband.

    A screen shot of SmartSDR while in TX will help others narrow down on the configuration issue to help you out.


  • W2ECK
    W2ECK Member ✭✭

    So I tried 60M FT8 with WSJT-X again yesterday after checking all those items everyone suggested -- and it worked !! So... it could have been - Fake It not turned on, of the LPF incorrectly set, not sure. But big thanks to all who replied to my post. Hopefully it's fixed for good.

    73 Paul w2eck

    Btw: I had never worked 60M FT8 before and have been quite surprised at 1) the activity level in the evening and 2) the propagation in the early evening here on east coast- worked Europe and the west coast.

  • kk6ivx
    kk6ivx Member
    This article was great. I was trying to reach E51D using m6400 and SDR3.4.21, The band was open on FT8 and the dang Interlock stopped me. The next day I went searching and found setup notes, after changing the bandwidth down to 2700 it worked.

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