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  • [Hackaday] Retro and New Tech Combine in this Hybrid Ham Transmitter

    From Hackaday via rec.radio.amateur.mode@21:1/5 to All on Tue Mar 1 06:23:26 2022
    XPost: rec.radio.amateur.homebrew

    amateur radio - Hackaday

    ///////////////////////////////////////////
    Retro and New Tech Combine in this Hybrid Ham Transmitter

    Posted: 27 Feb 2022 04:00 AM PST https://hackaday.com/2022/02/27/retro-and-new-tech-combine-in-this-hybrid-ham-transmitter/


    Weve said it before and well say it again: the best part about holding an amateur radio license is that it lets you build and use your own
    transmitting equipment. Hams have been doing this for more than a century indeed, it was once the only way to get on the air using whatever
    technology was available. But the mix of technologies in this low-power transmitter for the 80-meter band is something you dont see every day.

    As ham [Helge Fykse (LA6NCA)] describes in the video below, the project
    began when he came into possession of a bonanza of vacuum tubes 12A6
    tetrodes, specifically. The new-old-stock tubes were perfect for an RF
    power amplifier, but that left the problem of what to use for an
    oscillator. [Helge] chose to meld the old with the new and used oscillator board that he designed. The board has an ATmega88 microcontroller and an
    Si5351 oscillator, along with a 3V3 regulator to let the module run on 12 volts. And for a nice retro touch, [Helge] put the board in a 3D printed
    case that looks like an old-fashioned quartz crystal.

    There are some other nice design touches here too. A low-pass filter cleans
    up the harmonics of the oscillators 3.5-MHz square wave output before
    feeding it to the amplifier, in a nod to proper spectrum hygiene. The
    primary for the amps air-core output transformer is hand-wound, with 3D
    printed spacers to keep the winding neat and even. The tuning process shown below is interesting, and the transmitter was used to make a solid contact
    with another ham about 100 km away. And we really liked the look of
    [Helge]s shack, stuffed as it is with gear both old and new.

    Weve personally tried the Si5351 for QRP transmitters before, but this
    blend of the old and new really makes us want to find some tubes and get to playing.





    Thanks to [Stephen Walters] for the tip.

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