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5446Re: Remote tuning

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  • cmdrcosmac
    Jul 31, 2008
      --- In loopantennas@yahoogroups.com, "tenorman1952" <tenorman1952@...>
      > So, it occurred to me that it would be good to come up with a cheap
      > and easy way to turn a tuning capacitor <snip>

      That's basiclly a good idea and it's probably workable if the 180
      degree mod can be done
      with a servo powerful enough to turn the cap. The small tuning caps
      from cheap radios
      are usable in loops and turn easily. But these days remote tuning is
      usually done with
      a varactor diode. This replaces the cap and is tuned by a DC bias
      across it. This variable
      voltage is usually sent up the signal feedline, isolated by
      capacitors. Other posters on
      this forum have given links to examples of this.
      The servo would, however, be a good way to rotate the loop. You can
      find circuits on the
      web to operate the servo directly without the R/C stuff.


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