Cubical quad <A href="http://stats.superstats.com/c.cgi?u=kd6dks" target=_top><IMG border=0 src="Quad Antenna 50 MHz_files/CAMPGRIZ.htm"></A> CUBICAL QUAD ANTENNA CALCULATOR Enter center frequency to be calculated for a quad : mHz in INCHES/ CENTIMETERS Total Length ONE SIDE Spreader Arm Length ONE SIDE "C" Reflector Driven Element Director 1 optional Director 2 optional Director 3 optional Director 4 optional Director 5 optional INCHES/CM INCHES/CM INCHES/CM spacing between the reflector and driven element should be inches centimeters . spacing between the driven element and the first director and between the directors should be inches centimeters Gain vs Spacing The gain of an an antenna with parasitic elements varies with the spacing and tuning of the elements, and thus for any given spacing there is a tuning condition that will give maximum gain this spacing. The maximum front to back ratio seldom, if ever occurs at the same condition that gives maximum forward gain. The impedance of the driven element also varies with the tuning and spacing, and thus the antenna system must be tuned to its final condition before the match between the coax and the antenna can be completed. However, the tuning and matching may interlock to some extent, and it is usually necessary to run through the adjustments several times to insure that the best possible tunning has been obtained.