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Adjusting the KN4YB Bug

Following are suggestions for making initial dot adjustments on KN4YB’s excellent SL171 bug.  See the numbers on the photo for identification.

  1.  #1 is the at-rest dampener for the vibrating arm.  It should normally  be adjusted so that the rubber bumper is against the adjustment post.

  2. Adjustment post #2 is the resting stop  for the vibrating arm.  Adjust this so that it is touching the vibrating arm lightly when the arm is at rest against the rubber bumper, but not pushing it away.  When the vibrating arm comes to rest, it should not bounce but stop immediately against the rubber bumper.

  3. Post #5 holds the dampener blade for the dot contact.  It should be lined up so that the contact on it and on the vibrating arm meet precisely.  Using the supplied hex wrench as a lever (see Tom’s YouTube video), twist the post so that the blade lightly touches the rubber bumper on Post #4 (which should be backed out so that the rubber washer is against the post).

  4. Put a feeler gauge of about .015 between the Post #2 adjustment screw and the swinging arm of the paddle (see Tom’s YouTube video) and adjust #3 until the feeler gauge is lightly squeezed between adjustment crew #2 and the  swinging arm.  This provides the initial setting for the dot adjustment.

  5. Now adjust #3 for a good sounding dot string.  Tom suggests that you should get a good sequence of  about 10 dots.

  6. Use adjustment #4 to fine tune if necessary, though Tom suggests it usually works best to have the blade resting lightly against the rubber bumper washer.

  7. Adjust dot and dash tension to taste, and dash space similarly.

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