CUBICAL QUAD ANTENNA CALCULATOR
JavaScript PROGRAM by N6ACH Ron vanVarden

thanks to Scott McClements for the round off problem and to Roger KC5LCA for stream-lining the interface

Many hams and agencies have asked for, and received permission to take this program to use on their site or to modify for their use. I did not create the formulas, they are public domain, I just put it together with the help of Scott and Roger in a webpage.



Enter the center frequency: mHz 
All directors are optional
Elements
Element -
Total Length
Wire -
One Side
 Spreader -
Half Length
Spreader - 
Total Length
 Element -
Spacing
  INCHES / CM INCHES / CM  INCHES / CM  INCHES / CM INCHES / CM 
Reflector  
Driven 
Director 1
Director 2
Director 3
Director 4
Director 5
Total Boom Length > FEET= INCHES= CM=



quad
Drawing used with permission by Buck Rogers Sr.

spreader
C= Spreader arm Length
reflector

Reflector tuning stub 

How to mount and feed.

Horizontal or vertical polarization of an cubical QUAD-Antenna is determined by placement of the feed point (feed gap on the driven element) - Parasitic elements need to be mounted in the same orientation as the driven element. If tuning gap is present on the parasitic elements, doesn't the placement of this gap effect the polarization. Feed line is made out of standard coaxial cable (RG8/RG58) 50ohm unbalanced, to attach this feed line to the balanced drive element (Quad loop) without proper matching is not advisable, instead use an 1:1 balun

Gain vs Spacing

The gain of 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 tuning has been obtained.

If you have any hints, or comments, please e-mail me at n6ach@comcast.net .
73 de Ron

A downloadable .exe version of this script by KC5LCA is available from Ve3sqb....here