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5 watt amplifier kit

Discussion in 'The Low Bands - 630/2200 Meters - VLF' started by AE5X, Oct 8, 2019.

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  1. AE5X

    AE5X Ham Member QRZ Page

    KK4CUL likes this.
  2. WQ2H

    WQ2H QRZ Lifetime Member #214 Platinum Subscriber Life Member QRZ Page

    John - thanks for sharing this post, I've had a complete QRP labs set up w/2200 & 630 LPFs that I simply haven't had time to even start ! :eek:

    Don't know what kind of an antenna you have, but I can take a photo of my load coil / match xfrm used with my 40' vert w/ 100' hat if needed. Seems to work reasonably well for 475.

    In any event, I'll be listening.

    73
    Jim, WQ2H / WK2XAH
     
  3. AE5X

    AE5X Ham Member QRZ Page

    Hi Jim,

    The antenna will be my 80m dipole fed as a top-loaded vertical. It is about 100 feet tall and will have a coil at the feedpoint consisting of about 30 turns on a 5-gallon bucket. I take it down during the summer thunderstorm season - it will go back up this weekend. It makes a decent tx antenna but is noisy on rx so I'll be experimenting with a loop soon.

    73 - John AE5X
     
  4. WQ2H

    WQ2H QRZ Lifetime Member #214 Platinum Subscriber Life Member QRZ Page

    Nice - sounds good. I use about 150uH with my short Marconi (and the match torroid is biased about 6/26 toward ground). I'm guessing 30 turns of 14AWG on a bucket would probably be twice that.

    Tis' the season for MF/LF, so enjoy !!


     
  5. AE5X

    AE5X Ham Member QRZ Page

  6. WQ2H

    WQ2H QRZ Lifetime Member #214 Platinum Subscriber Life Member QRZ Page

    Good job John - great write-up. You'll be bagging QSO's before you know it ! :)

    Here's what I use for 630. It fits in a 2 1/2 gallon pail. So far I've put 100W TOP into it, yielding almost 1 W.

    https://www.n1fd.org/2019/10/27/630m-match/
     
    KK4CUL likes this.
  7. KK4CUL

    KK4CUL Ham Member QRZ Page

    How warm does the torroid get? That's a lot of power to dissipate!
     
  8. WQ2H

    WQ2H QRZ Lifetime Member #214 Platinum Subscriber Life Member QRZ Page

    I measured ~ +25C (+77F) after a 2 minute WSPR Tx.

    Have never actually measured anything higher - although the "ambient" is dropping fast here in New England. :)
     
  9. AE5X

    AE5X Ham Member QRZ Page

    I never thought to check the temp of the toroid. I'll have it on tonight but just spent the day installing the amp into an aluminum housing and want to see how that works with heat dissipation. The heat sink is the case itself along with an SO-220 type heatsink external to it. I really don't see a problem with the final transistor or the toroid - heat build-up has been minimal. Instead of heatsink, I'm gonna call it a lukewarmsink even though my spell checker is calling me an idiot.
     

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