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Thread: Zetagi amp mod

  1. #1

    Zetagi amp mod

    I am going to get bushwhacked on this one but here goes:
    I came to the hobby via cb. I have an old Zetagi 550p (4x mrf455) gives around 300w ssb with a 20w drive. Ok, it doesn't have filters. But if you replace the 6 level attenuator board with a decent 6 band pass filter-board (I can construct one) it should pass muster. The snag is it is supposed to be only usable on 20mhz and up. I want to use it on 20m n 40m if possible. Any ideas to make it a decent 300w amp on these freqs? I can provide the circuit which is available on the 'net.

  2. #2
    Administrator N8YX's Avatar
    Join Date
    Feb 2007
    Akron, OH
    IIRC, the '455 is usable from 13-30MHz @ rated IMD and gain.

    I'd have a really close look at the Application Notes for that device before doing anything. Gain compensation will undoubtedly factor into such a modification, thus necessitating rework of the biasing and output circuits.

    Speaking the output transformer design and core types to those spec'd in the Notes. Is the mix and permeability suitable for lower HF operation w/o causing core saturation? Another possible gotcha.
    "Everyone wants to be an AM Gangsta until it's time to start doing AM Gangsta shit."

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