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4cx5000 help

Discussion in 'Home Brew' started by Snake753, Aug 30, 2018.

  1. nomadradio

    nomadradio Analog Retentive

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    I got to where I can't operate an amplifier without a 'scope on the output.

    Let alone troubleshoot it.

    Just seeing if the modulation peaks are reaching double the amplitude of the carrier would reveal a lot.



    When your AM PEP is four times the carrier power, a Bird should hold steady with modulation, or kick up just a little.

    I'd be happy with 12kW peaks on that tube.

    Eimac's advice for the filament on that tube is pretty clear. 5 percent regulation. The procedure for a broadcast transmitter was to reduce filament voltage until RF-output power just begins to fall. Bring it back up just above that point for longest operating life. This is not so clear-cut for the transmitter in a 2-way system.

    73
     

  2. Shockwave

    Shockwave Sr. Member

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    While I'd be happy running that tube at a 3kw carrier and 12 kw PEP, I wouldn't be so happy knowing that this was all it could produce because it lacks headroom where there should be plenty. The 4CX5000A should have enough peak emissions to produce double that in ICS. Even a 3CX3000A7 can hold about 6kw on the Bird with a strong tube and power supply. The 4CX5000A has a third more filament current to support more emissions but this amp is not showing that capability yet. This tubes internal structure is identical to the 4CX10,000D but just has a smaller cooler. Something is holding it back.
     
    #32 Shockwave, Oct 27, 2019
    Last edited: Oct 27, 2019
    Shadetree Mechanic likes this.
  3. nomadradio

    nomadradio Analog Retentive

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    Sho 'nuff.

    Had lost track of that detail.

    73
     

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