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Cubical Quad Antenna Calculator

This calculator requires the use of Javascript enabled and capable browsers. The function of the calculator is to give all of the needed sizing to construct a good 5 element quad antenna for amateur radio use. This calculator requires only the entry of the center of the frequency range your quad antenna will be used in. Our default is 29mHz. Click on Calculate to display the critical antenna measurements in both inches and centimeters.

The optimum gain of any antenna with parasitic elements varies with the spacing and tuning of the antenna's elements. This ALWAYS require manual tuning and optimization.

It is very unusual for the optimum front to back ratio matching the same condition that gives maximum forward gain; some compromise is probable and is in order. The impedance of the driven element also varies with all tuning and spacing operations. Hence, the antenna system must be tuned, probably several times in small increments, to its final condition before the final match between the coax and the antenna can be completed.

The antenna can be fed directly with standard coaxial cable (RG8/RG58) 50ohm unbalanced, however, in most cases a 1:1 balun is used to significantly improve matching. It should also be noted that for vertical polarization feed, the driven element is fed from the side of the diamond or square, and for horizontal polarization feed the driven element is fed at the bottom of the diamond or square, depending on your mounting orientation.

Quad Beam Calculations
Required Data Entry
Anticipated Antenna Frequency mHz

Calculated Results
Total Element Length
Element Length
One Side
Spreader Arm
Length (1 of 4)
Inches Centimeters
Inches Centimeters
Inches Centimeters
Reflector or or or
Driven Element or or or
Director 1 or or or
Director 2 or or or
Director 3 or or or
Director 4 or or or
Director 5 or or or
Reflector To Driven Element in or cm
Driven element To First Director in or cm
Director To Director in or cm (2-5 Optional)
Total Boom Length in or cm End To End
Updated 8.02.11

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