GI7B

Discussion in 'General Technical Questions and Answers' started by YO9ICT, Jun 25, 2010.

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  1. YO9ICT

    YO9ICT Ham Member QRZ Page

    Hello everyone.
    I want to ask what is the maximum output power from a GI7B triode and at what anode current in the following cases:
    HF, 1KV
    HF, 2KV
    VHF, 1KV
    VHF, 2KV

    because I plan to make a supply and for me it's more easier(and cheaper) to make for 1-1.2 KV.
     
  2. W3DRK

    W3DRK Ham Member QRZ Page

    You can easily calulate this by guestimating 60% efficiency and using the triode's 350 watt plate dissipation rating. I'd do it for you but I'm posting this reply from a cell phone. ;)
     
  3. W8JI

    W8JI Ham Member QRZ Page


    I looked at the characteristic curves for the GI7B for you, and the plate current knees over at about 700-800 volts. This means you would compromise linearity and efficiency greatly with an anode voltage of 1000 volts or so.

    It would NOT be a good idea to start at 1000 volts.

    I have not done (and will NOT do) a Chaffe analysis for that tube, but it looks like linearity and efficiency will not be acceptable unless you have at least 2000 volts.

    At 2000 volts a rough look tells me it would be around 50% plate efficiency. Maybe a little more. That means about 300 watts output CCS and maybe 400-500 ICAS if you tolerate reduce IM performance.

    It looks like to me you would want to be at 2500 volts or higher for best efficiency and IM performance.

    I'm basing this on other tubes I have worked with that have similar characteristic curves. With lower high voltage, it will have lower efficiency and much poorer the IM performance.

    73 Tom
     
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