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F/H mode FT8

I am unsure of a few things when operating FT8 using JTDX v2.2.159 / 6600M v3.3.33. A number of DXPeditions use F/H mode. Selecting ‘Hound’ in JTDX opens a warning: “Hound TX frequency control requires Split (either Rig of Fake it…)”.  

Selecting ‘Rig’ opens a second slice 1KHz higher. I understand in F/H mouse all transmissions below 1kHz are ignored so that seems logical. If ‘Fake It’ is selected I see no change, i.e. no second slice.  

Why can’t I just select a suitable TX frequency (>1kHz) on the JTDX waterfall without selecting either Fake It or Rig?  

Another question: I’ve noticed that with sought after DX stations some callers include their locator whilst others don’t. Personally I never include my locator on ‘non DX’ contacts as it just slows down the exchange and could always be confirmed via qrz.com anyway. Is the situation different in F/H mode? 

Jeff – G4IUA

Best Answers

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

    What if you live in a very grid in U.S. but you are operating from a rare grid? Without the locator, the station working you does not know your location. Just saying… there are people who chase grids.

    As far as rig and Fake It, that is part of how WSJT-X (and JTDX) were written. When using Hound mode the software will prevent you from calling below 1000 Hz. It also keeps your TX signal from the radio going out between 1500 and 2000 Hz. This helps keep images of your signal out of the TX passband (important for rigs where the op is overdriving the TX audio input.)

    Dave wo2x

  • Martin_G4ENZ
    Martin_G4ENZ Member ✭✭
    Answer ✓


    Choose "Fake it". Click on the Fox's decoded signal to populate the messages. Choose a suitable frequency, above 1000Hz, you imagine might be clear to TX on. Then, Click the "Hound" Button and "Enable TX".

    When the DX calls you and gives you a report, JTDX will move your TX frequency to below 1000Hz so that you can transmit a report, in clear space, to the DX. The DX should acknowledge you with RR73 and the whole process is over.

    Calling with your locator is OK. Calling without it won't speed up F/H.

    73 Martin - G4ENZ

  • Erik Carling EI4KF
    Erik Carling EI4KF Member ✭✭✭
    edited November 2022 Answer ✓

    JTDX takes advantage of the Grid Square if you are the run station calling CQ, especially if you are not using a directional CQ like CQ AS, CQ NA or CQ AS (which stops the software answering to EU). In menu>Autoseq with Max Distance checked, JTDX will compute which respondent is further away so will answer to the longer distance station when more than one answers you i.e. DX preferred over EU.

    Other than that the Grid has less purpose on bands other than VHF/UHF. I always call a station with the report as it gets the essential info through asap.

    As for F/H yes you are correct, the Grid is mandatory. The F/H protocol is badly flawed. Not just with having to send useless info but in a crowded FT8 band with a huge number of Hounds chasing something rare, a third of the band (1kHz out of 3kHz) is a no-go area for calling. Sure, space is needed to respond to the DX in a clear area but the calling area should be 500hz and up. We just have to live with it, it is what it is.


  • G4IUA
    G4IUA Member ✭✭

    Thanks both for the input.

    Re the grid square: I’m surprised so many use their locator in a DX pileup as it would be of little interest to the DX station. I’ve experimented using the ‘Fake’ option and confirmed the TX VFO moving as described. Actually the ‘Skip TX1’ box is greyed out when Hound is selected so there’s no choice anyway.

    Jeff – G4IUA

  • G4IUA
    G4IUA Member ✭✭

    Thanks Erik, especially conforming the need for using the locator in F/H mode. As you suggested it is a limitation of the protocol. A rare DX station isn’t remotely interested in our locator.

    Thanks too for the reminder re ‘max distance’ filtering - a potentially useful feature I’d forgotten about.

    jeff - G4IUA

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