Turning the 6DC6 into a 80m preamp for a reciver.

Discussion in 'Homebrew and Kit Projects' started by KC9OXP, Feb 28, 2009.

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  1. W0BTU

    W0BTU Ham Member QRZ Page

    Who will donate the other part?

    Ok, who has a 2N5109 (or 2N3866) to donate to this young man? I'll mail the other parts as soon as someone commits to mail the bipolar to him.

    73 Mike
     
  2. AC0OB

    AC0OB Subscriber QRZ Page

    PArts for OXP

    I have the NTE equivalents and if Oscar Xray Papa will send me a PM with his address I'l send him one.
     
  3. KC9OXP

    KC9OXP Ham Member QRZ Page

  4. W0BTU

    W0BTU Ham Member QRZ Page

    Preamp parts

    I have the parts together along with my original schematic (which has the transformer information). I also threw in a heat sink for the transistor. I'll try to mail them tomorrow.

    The schematic doesn't show input protection. I have a couple of back-to-back 1N914 diodes between the input and ground to help protect the transistor. I lost several transistors to static discharges before I did that.

    73 Mike
     
    Last edited: Mar 5, 2009
  5. KC9OXP

    KC9OXP Ham Member QRZ Page

    Thank you both!
     
  6. W0BTU

    W0BTU Ham Member QRZ Page

    Silicon diodes

    You're very welcome.

    In response to your question, yes, you can use silicon diodes as are used in power supplies, like 1N400*. I've used those and 1N914 switching diodes to protect the inputs of various preamps I've built. I'll see if I have some that I can include in your package.

    73 Mike
     
  7. W0BTU

    W0BTU Ham Member QRZ Page

    Preamp Construction details



    Hi Mike,

    The parts are on the way to you. It was very kind of KD0GIW to send you the transistor.


    I threw some photos of the preamp up on one of my web sites:

    http://www.negativeiongenerators.com/_w0btu/W0BTU-broadband-preamps.html


    The schematic there is not the best. I drew it around 1982. Note that you only need two ferrite beads.

    As you'll see, the transistor I'm using does not have a heat sink, but W7IUV recommends one for the 2N5109. That's why I included a heat sink. It's not the biggest one in the world; If the 2N5109 gets too hot too touch, I suggest you shut off the preamp and get a bigger heat sink.

    I included a couple of photos from some other preamps I've also built, which show the transformer more clearly. (I don't remember offhand what the solid state device is on the back of the two PCB's. There's a schematic around here somewhere, but I haven't seen it since I've moved to this QTH.)

    Let me know if you have any questions.

    73 Mike
     
  8. KC9OXP

    KC9OXP Ham Member QRZ Page

    I received both of your packages today (3-9-2009). Same day that I started my schooling for computer and electrical engineering at itt tech. So busy day. I started assembling it. Got the transformer made and mounted and the transistor, goopped & heat sinked and mounted. Not for sure yet when it will be complete. But I plan on working on it some more today before school.

    Also is the extra beed just for back up or do I need to wrap another?
    How do I install the anti static diodes? Do I put them so its ground and input or just feed the input through them?
    Is ceramic, Mylar, polystyrene capacitors interchangeable on this? So long as the ƒ are the same.
     
    Last edited: Mar 10, 2009
  9. W0BTU

    W0BTU Ham Member QRZ Page

    Hi Mike,

    You don't need the extra bead for the preamp.

    The diodes have to go from input to ground; on the side of the series capacitor towards the antenna and NOT connected directly to the transistor's base.

    I would use disk ceramic capacitors. They have low inductance and are not going to have any odd resonances.

    73 Mike
     
    Last edited: Mar 10, 2009
  10. KC9OXP

    KC9OXP Ham Member QRZ Page

    I am working on the final stages of it. I am wondering what the current draw is? I'm building a power supply for it that independent of my master source, not sure what size of transformer to use current wise.
     
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