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 
C= Spreader arm Length
Reflector tuning stub 
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. 

 


 



                   Number of                Gain             Front-to-back ratio     Comment
                   Elements              (Over Dipole)            (F/B ratio)


                       2                         5                     12               Reflector element only
                       2                         7                      0                Director element only
                       3                        10                     15
                       4                        12                     25
                       5                        12.1                   30
                       6                        12.2                   30
                       7                        12.3                   32
                       8                        12.4                   32


                 Note: Typically, the gain will be within 2 db of the indicated gain. However,
                        front-to-back ratio can vary greatly (as much as 25db) from the
                        indicated F/B.