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40M Push-Pull amplifier with IRF530/510

Discussion in 'Homebrew and Kit Projects' started by SA7CNG, Jun 20, 2018.

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  1. SA7CNG

    SA7CNG Ham Member QRZ Page

    I am looking for a way to get more power from my "QRP" 40 CW beacon, that produces about 9-10W from 24v. I thought i would try to build this circuit:

    I'm a bit unsure about how to wind T1, but i will try to do 12turns "trifilar" over a FT50-43, then connect 3 of the wires to GND, 1 end to the R8/R10 point, and the two others to R1/R2(not gnd end). Does this sound right?

    Last edited: Jun 20, 2018
  2. SA7CNG

    SA7CNG Ham Member QRZ Page

    I didnt have two T37-43 for T2, so i used two T50-43 instead. T3 is however a bit different, and hard to find. I have ordered one online, but havent received it yet. Could i try to use a couple of T50-43 instead?

    And how should i wind it? It sais 2:3 turns, but does that mean two on the transmitter side, and three on the antenna side? Or is it only the ratio between them?

    KA9JLM likes this.
  3. VK4HAT

    VK4HAT XML Subscriber QRZ Page

    For T3 you can make a binocular core out of 4 t50-43 and a little super glue. 1 turn primary 2 turn secondary should be about right.

    Once you have this built and tested, try and build a class E amp for 40m using the IRF fets and see what power you can get out. Should be high, class e is about 90% effecient
  4. AI3V

    AI3V Ham Member QRZ Page

    Also, try more or less turns on the transformers, maybe you will pick up a bit more gain, power or efficiency.


    P.S. love the breadboard :)
    K6CLS likes this.
  5. N1OOQ

    N1OOQ Ham Member QRZ Page

    Love the project. I don't know if a high-powered beacon on 40m will win you many friends, however...
  6. VK4HAT

    VK4HAT XML Subscriber QRZ Page

    As long as it complies with local regulations :)
  7. SA7CNG

    SA7CNG Ham Member QRZ Page

    I was made aware by a couple of fellow hams that my transmissions were causing interference in the QRP part of the 40m band, this was not my intention. I have therefore stopped the beacon, and halted this project. I am sorry for the disturbance i have caused the CW operators.
  8. N1OOQ

    N1OOQ Ham Member QRZ Page

  9. VK4HAT

    VK4HAT XML Subscriber QRZ Page

    Keep the project going, do not stop it, just modify it to be an actual CW transmitter with a CQ auto caller. Add in a key and win. Then with your auto caller, have it call cq cq de sa7cng sa7cng rbn test calling 3 times in ar row is enough to get picked up on RBN its does not need to run flat out 24/7 just enough to be useful as a propagation guide, go to the bottom part of the band 7.001 or the higher part of the cw portion 7.051 etc you will still get picked up on the RBN and will not annoy the die hard cw rag chewers. Use a DDS or PLL synth and an arduino to get the frequency agility if you do not have rocks that will take you there.

    You have not been taken off the air, you now have scope creep for your project. After you have the TX, add in an RX. Let her grow.
    VK3YE likes this.
  10. N1OOQ

    N1OOQ Ham Member QRZ Page

    Yes indeed, don't let that nice amp go to waste!
    KC8YLT likes this.

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