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FT991a external tuner control

Discussion in 'Homebrew and Kit Projects' started by DO7GUN, May 2, 2020.

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  1. DO7GUN

    DO7GUN Ham Member QRZ Page

    Hi all,
    I'd like to remote control a Stockcorner JC-3s tuner with the Yaesu FT-991a.
    So far, tuners of this small dutch company are not very friendly with Yaesu transceivers. One needs to use a control box with three elements:
    • An LED informs if the tuner is in tuning mode (KEY)
    • A switch to activate / de-activate tune memories
    • A push button (closing a circuit when pushed) for putting the tuner into tune mode (START)
    Unlike their ICOM counterparts, Yaesu transceivers do not communicate with Stockcorner tuners. Likewise, the tuner does not switch to tune mode automatically when the SWR gets too high. According to stockcorner, Yaesu is missing a "start-key" logic.

    Tuning is engaged manually and requires manual TRX settings. When the push button pressed, the tuner switches to tune mode and expects the TRX to send a carrier between 10-20W for enabling the tuner to match on the frequency. This button is pressed just momentarily. The tuner remains in tune mode for 10s or until tuning is finished. During this time, the LED of the control box is lit up. When tuning is finished, or after 10 seconds, the LED turns off.

    I'd like to get rid of the control box and control the tuner via the TRX.

    At least as in so far, as that I want to engage tuning mode of the tuner via built-in functionality of the FT-991a. The "TUNE" mode might not be the answer, it is just my first thought.

    The FT-991a has TUN/LIN jack with 8 ports on the back. This jack is used to control Yaesu auto tuners and key up amplifiers. I could use this jack also to supply power to the tuner, since the control box has leads going into the power supply and takes 12v.

    From my understand I need to solve the following:
    1. Create a custom miniDIN 8 port plug which gives the FT-991a the illusion an external tuner is attached, so I can tune with the "TUNE" button
    2. Find out if pressing the "TUNE" button simply closes a circuit (I hope) or sends a complex signal to the expected Yaesu tuner (that would make my life harder)
    3. Find out on which pins such a signal is located.
    4. Create a circuit that feeds a START signal to the tuner when the "TUNE" button is pressed (or any other FT-991a induced action). The START signal is send by momentarily closing a 5V circuit coming from the tuner.
    5. Optional: route the signal for the LED (KEY) to an ESP2866 or something to give me indication if tuning was successful (I can see that otherwise with the SWR meter, d'uh).
    Does anyone have experience with something like this?

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