Hey Rich,
A repeatable signal is one that gives about the same sound effect for both righthand and lefthand sweep directions.
Some signals are repeatable at only limited swing angles. For example, you may dig a mercury dime that does not repeat for every swing angle. Imagine that your target of interest is in the center of a time clock, and that the centerline of your search coil is aligned at 12:00. While you are sweeping right and left, you are sweeping at the twelve o'clock swing angle. To test a signal, you can test each swing angle (12:00, 1:00, 2:00, etc.) for signal repeatability. Imagine that you are sweeping over an object and that it will only repeat for swing angles of 5:00 thru 7:00. You dig down and find a mercury dime.
Most coins that I dig will be repeatable for some range of swing angles. Many trash items I dig are repeatable for some range of swing angles too!
Mike
