Thursday 25 July 2013

Homebrew variable capacitor

A year ago I made this 20...200 pF variable capacitor. It is used in a magnetic loop antenna for 80m. The plate distance must be large enough to withstand the high voltages that exist at the magnetic loop antenna's top (levels of over 1 kV are easily reached).





The static plates are made of pieces unetched PCB. The variable plates are aluminium. This capacitor works fine in my magnetic loop antenne. I have been able to made some QRP contacts on 80 m with it without the use of a long wire antenna. Still handcontrolled. Remote control would be a nice improvement.

7 comments:

  1. MY first comment in your new blog, Ron. Keep up with the good work!

    Just one idea I am thinking, what about using an M6 threaded bar as the axis for the variable plates, so one can use regular potentiometer knobs for tuning? If M6 is not 6mm diameter, use the closer one and a big button for tuning/dial... Just a simple idea... Tot straaks!

    ReplyDelete
  2. Thank you for your input Juanjo,
    Sounds like a good idea. I choose the option with a big "wheel" so you can make small changes. A smaller knob would make fine adjustments more difficult. The final solution is of course a remote controlled capacitor. You do not want to be close to the antenna while tuning ( hi field strengths ).
    Muchos gracias
    Ron

    ReplyDelete
  3. This comment has been removed by a blog administrator.

    ReplyDelete
  4. This comment has been removed by a blog administrator.

    ReplyDelete
  5. This comment has been removed by a blog administrator.

    ReplyDelete
  6. This comment has been removed by a blog administrator.

    ReplyDelete
  7. This comment has been removed by a blog administrator.

    ReplyDelete