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What is the "Plate" on a tube radio?

Discussion in 'Home Brew' started by T23, Oct 5, 2010.

  1. T23

    T23 Active Member

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    Could someone explain what the "Plate" is on a tube radio?


    T23



     

  2. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    The plate is also called the anode. It is the tube element that gets connected directly to the high voltage supply and attracts the electrons. It is where the output of the tube is taken from.It is typically the largest element in a tube.
     
  3. is this the same "plate" that people are referring to when they talk about "plate modulation" ?
     
  4. T23

    T23 Active Member

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    Well see what I am trying to do is run a signal into a AM Braodcast band receiver an use the RF leakage as a transmitter, like if you put another AM radio right near it and tune it to the same frequency one of the radios goes quiet...

    I know it sounds crazy, but I ain't the one who came up with it, I can provide a link to clarify things if needed...


    T23
     
  5. TonyV225

    TonyV225 W9WDX Amateur Radio Club Member

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    Yes hence the term Plate Modulation
     
  6. Shockwave

    Shockwave Sr. Member

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    It's not crazy but you are probably expecting better results then are possible here. The oscillator in the tuning stage of the receiver will generate a small signal that is offset from the tuned frequency by 455 KHz. One of the first rules of deciding where to apply modulation is to always avoid directly modulating an oscillator stage. Any changes from varying the plate voltage with audio to adding an antenna to the oscillator will cause noticeable frequency shift. If you try to amplitude modulate the oscillator you are likely to end up with as much frequency modulation as amplitude. The oscillator stage must be modulated after a buffer stage to prevent frequency drift. Unfortunately that's not the way the broadcast receiver is designed. The oscillator is followed by a mixer to feed the 455 KHz IF strip. For safety reasons, don't forget the plate also has high DC voltage on it.
     

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