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Home-brewing a Plate modulated Push-Pull 810 deck

Discussion in 'Amplitude Modulation' started by W2BTK, Aug 29, 2019.

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  1. KC2ZFA

    KC2ZFA Ham Member QRZ Page

    another way to balance unbalanced pp tubes is on the grid side, like in the pic with that 12pF variable cap to ground added in the MB40 they use.

    Attached Files:

  2. N2DTS

    N2DTS Ham Member QRZ Page

    I knew you were going to say that!
    It was long ago, and I never had a problem with those caps. (back then)
    I know its not a good idea.
    I like the heat sink type tube caps (with set screw), get the heat off the plate cap...

    {Nice looking job, but one problem I see is that you used those crappy ceramic plate cap connectors that were effectively designed to pull the plate caps off tubes when you try to remove them if they have been in place for any length of time (speaking from experience). Good 812s are too hard to come by, to risk destroying them with those things!}
  3. K4KYV

    K4KYV Subscriber QRZ Page

    Balance or unbalance in grid current has little effect on plate current balance in a push-pull plate modulated class-C final, since both tubes are driven well past the saturation point, where any further increase in grid current of the tube does not produce a further increase in plate current. Grid current balance would affect plate current balance in a push-pull class-B linear amplifier, or in a grid modulated final, since in those classes of service the tubes are not driven to the saturation point, except perhaps right at the crest of modulation peaks.

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