Posted by: m1paf | October 15, 2009

Progress resumes

After lengthy delays I’ve finally sourced the components I need to finish the tuner.

Scouring the web for a pair of matching roller inductors has lead me up a number of blind alleys and finally Palstar in the US have come to the rescue. Paul at Palstar was very helpful and I trust his products – I have one of his tuners in the shack here and it is bombproof. I’ve gone for 20uH inductors which should be plenty big enough:


The remaining task is to decide how I lay out the tuner. I can either mount the inductors parallel to one another and use a toothed belt to couple them, or mount them end to end with an insulated coupling between the shafts. Either way I can maintain mechanical symmetry so I might try both to see if there are any advantages. I also need to arrange end of travel limit switches for the rollers which should be straightforward.

Hopefully progress will pick up now and I’ll get the job done before winter is out.

73 Paul M1PAF



  1. VERY nice, I’m quite jealous 🙂
    Just for info, the companion card for Hermes will have an Atmel based ATU, the algorithm might be worth a look, I’ll shout as soon as the source code is available – still very early days on this as I type.
    Kevin – M0KHZ

  2. Hi Paul,

    Glad you have found inductors. I have had quite a saga in obtaining mine. The Palstar ones look quite solid.

    I now have two 1.5 KV double gang variable caps and two roller inductors. Am now grappling with programming microprocessors. Ah, decisions, decisions!

    Watching your progress with great interest and thanks for sharing your journey on the web.


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