First Homebrew HF power amp

Discussion in 'Amateur Radio Amplifiers' started by N7GTB, Jan 9, 2012.

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  1. N7GTB

    N7GTB Ham Member QRZ Page

    Hi Ken,

    I hope to have a few more soon. Progress has not been as rapid as I had laid plans of mice and men I guess. My new hours of 'freedom' seem to be gobbled up by other concerns lately. The current phase of the build, is simply to get as much of the metal work done early; so I can proceed with assembly. :)

  2. WA7PRC

    WA7PRC Ham Member QRZ Page

    Better to take your time and produce a good product you can be proud of, than to rush it and wind-up with something you'd rather keep under wraps. If humans were prefect, products would not need one (or more) development phases. Everything would start out at Rev A, and there'd never be a higher revision. Take your time.

    My 160m GS-35b project eeks along at a snail's pace. The only development was receipt of the last part for the output tank, a roller inductor (MFJ/Ameritron #404-1032):

    This will allow me to drive anything from about ZLOAD = 20Ω to 500Ω. Now that my big tower is finished and signed off, I can focus on the amplifier project. :)
  3. K9FV

    K9FV Ham Member QRZ Page

    Bryan - that looks like a NICE roller inductor. Looking at the silver plated edge wound coil looks a lot like some of MFJ's stuff. I was there once and saw where the rolled those things..... Oh, wait, now I see the MFJ part number. They do have some good parts.... and good products.

    Be sure to keep us posted (with photos) of your GS-35 amp.

    Vern - take your time and do it right from the start. I have a real problem with that, making sure the outside looks good.... I do need to do better.

    73 de Ken H> K9FV
  4. N7GTB

    N7GTB Ham Member QRZ Page

    Hi Bryan, Ken,

    No worries there. I'm a visual person, building projects in my head at least a couple of dozen times, before making a move...even then, it's sometimes hard to see progress. I'll still make mistakes along the way...that's a given. :) But given that I haven't yet started constructing the HV PSU; I'm 'guesstimating' that it will be sometime next spring, before I actually have the amp ready for final 'smoke test'.

    ...I have in the last few days however, produced more aluminum shavings; drilling holes for the main components, and part of the chassis/RF deck. It was decided early on, that the RF deck would be built in such a way, that it could either be rack mounted; or housed in a cabinet sitting on a pedestal (somewhat like the old Henry Radio amps). The HV PSU could either be on a separate deck in the rack, or mounted within the pedestal... I don't know that I'll ever own a rack-mount cabinet. I do like having the flexibility to use one, should it come into my possession. Until then, the pedestal arrangement will fit well in the 'shack'.

    That's a nice roller inductor, can't wait to see it mounted in your amp... :)

    Last edited: Sep 3, 2012
  5. WA7PRC

    WA7PRC Ham Member QRZ Page

    The roller was meant to be used in a tee ATU (Ameritron ATR-30) with one end on ground. But, it'll be easy to work around that. I have an outer case for a SB-220 (with meters, knobs & rocker switches). The idea is to match the style of my existing SB-220 (yes, it will be green). Only the front & rear panels for my will need to be made "pretty" with paint and lettering. I may cheat and have the lettering & line art silkscreened from a CAD file (Visio).

    My PS is also first. I need to connect with a local xfmr shope to have my xfmr dipped. The PS will be a full wave doubler with plenty of overhead (close to 100%). Modelling in LTSPice shows ripple (under 1A load) to be only about 20V. Dynamic stability (load regulation) figures to be about 4% with a 1A load. Actual worst-case load is expected to be about 785 mA.

    Start with NOT using Dymo-type labeling. :p

    Me too. ;)
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