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Thread: First Homebrew HF power amp

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  1. #31

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    I dont consider a simple discussion a peeing war but if youre not able to offer more than that so be it.
    I'm quite ABLE but UNWILLING to "discuss" this with you.

    Finito (meaning, I won't be revisiting this thread again).

  2. #32

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    I'm quite ABLE but UNWILLING to "discuss" this with you.

    Finito (meaning, I won't be revisiting this thread again).
    I guess thats better than having to admit making a mistake or accepting that there are other valid opinions in your eyes....SOP.

  3. #33

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    Quote Originally Posted by N7GTB
    BTW, you're the second person to mention/recommend using a control board.
    I've not had a chance yet to fully read up and understand their benefit.
    In a nutshell, what function do they serve?
    SIMPLIFICATION for the DIY Builder of the various Regulation, Control, Monitoring, and Display electronic circuits
    of the RF Power vacuum tube operation in the linear RF amplifier.

    There are 2 well known suppliers for control boards (DIY Builders):

    One is Paul Hewitt, WD7S - who offers a Triode Control board as well as many other
    assemblies/modules (band switchable tuned input) for the DIY Builder
    http://home.earthlink.net/~wd7s/triode_control.htm

    The other is G3SEK/GM3SEK in the UK, who offers a Triode and a Tetrode Control board (as well as kit of parts and board).
    http://www.ifwtech.co.uk/g3sek/

    w9gb

  4. #34

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    Quote Originally Posted by AG6K View Post
     For a full 1000w in linear service, 6. 811As would be better since they have rather low anode dissipation capability and they are not very linear above 200mA. However, since each 811A has 0.6pf of C-feedback, you will be dealing with a total C-fb of 3.6pF - which means that you will need to use better than avg. - a.k.a., lower-Q - VHF suppressors to keep the squirrels away. With 6, 811As and minimal fil.-V your tubes should last a long time Vern.

    Rich, ag6k.
    I stumbled into a few 811a's for not too much out of pocket... I also made a concerted effort to dig into my junk boxes...found ceramic sockets, and some other parts that I think might work. I'm intrigued by this and have decided to start working on it. I've also sent away for a Russian tube (GS35B). Once I have more time (this summer or next fall) I'll begin building around that tube as well...

    I don't know if I'll manage 6 811As, but for the sake of argument seems like some increased airflow might be required...(?) 6 bottles in tandem sounds cool as all get-out.

  5. #35

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    I stumbled into a few 811a's for not too much out of pocket... I also made a concerted effort to dig into my junk boxes...found ceramic sockets, and some other parts that I think might work. I'm intrigued by this and have decided to start working on it.
    Hi,
    Great that you going for the 811a's! It would be great to know how it advances for you. Post some pics of the progress. Here is my 811 build: (almost done): http://gallery.me.com/ulf.tjerneld#100183

    73's
    Ulf

  6. #36
    Join Date
    Oct 2003
    Location
    Middle Georgia USA
    Posts
    7,722

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    Quote Originally Posted by N7GTB View Post


    I don't know if I'll manage 6 811As, but for the sake of argument seems like some increased airflow might be required...(?) 6 bottles in tandem sounds cool as all get-out.
    Good luck on that.

    Four tubes require neutralization and barely work on ten meters.

    Unless you plan on staying below 20 meters, I'd limit to 4 tubes.

  7. #37

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    Quote Originally Posted by W8JI View Post
    Good luck on that.

    Four tubes require neutralization and barely work on ten meters.

    Unless you plan on staying below 20 meters, I'd limit to 4 tubes.
    Shouldn't be too much of a problem... I seldom go up to 10m, and when I do my beam seems to get me anywhere I want to go. It's the lower bands where I would like the boost. 160m in particular is always a struggle... As I said, 6 tubes may be a bit much. By my calculations, the filaments alone will require 24 amps and I still need to come up with a suitable plate transformer for even four 811As.

  8. #38
    Join Date
    Jun 2010
    Location
    logansport in.
    Posts
    382

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    I built a 6 tube 8-11 amp 25 years ago and was very happy with it at 15 and down. It did work on 10 but had problems. I just used it on 15 and down. It produced as expected with 1500 volts on the plate for an easy 750 watts and a stretch to hit a KW.
    Joe

  9. #39

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    Quote Originally Posted by SM0NOR View Post
    Hi,
    Great that you going for the 811a's! It would be great to know how it advances for you. Post some pics of the progress. Here is my 811 build: (almost done): http://gallery.me.com/ulf.tjerneld#100183

    73's
    Ulf
    Great looking amp! I see the schematic for the power supply... do you have one for the amp that you'd be willing to share ?

  10. #40

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    Quote Originally Posted by KA9UCN View Post
    I built a 6 tube 8-11 amp 25 years ago and was very happy with it at 15 and down. It did work on 10 but had problems. I just used it on 15 and down. It produced as expected with 1500 volts on the plate for an easy 750 watts and a stretch to hit a KW.
    Joe
    Joe... Sent you a PM...

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