Hi Ray,
Taken directly out of the ARRL antenna book,
Driven = 1008/f (MHz)
Reflector =1045/f (MHz)
Director = 977/f (MHz)
Valid for quad antennas using uninsulated #14 stranded copper wire.
Element spacings are in the order of 0.14 to 0.2 free space wavelengths.
HTH
Gary
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