NEC-LIST: How do I simulate a CARDIOID Array?

I am experiencing problems in simulating a cardioid array at
300MHz. The array consists of two vertical ½ lambda dipoles,
stacked horizontally with a separation of ¼ lambda. The dipoles
are fed with equal magnitude and 90 degrees phase difference.

These are the requirements for a cardioid pattern as detailed in
Antennas by J D Kraus 2nd ed. pp.452. Included on pp.452. are 30 polar
plots for various dipole spacing and phase differences. They were all
simulated and gave expected results (OK) or wrong results (X):

                  Phase Difference

     Spacing 0 45 90 135 180
     ------------------------------
     1/8 lambda OK X X X OK
     1/4 lambda OK X X X OK
     3/8 lambda OK X X X OK
     1/2 lambda OK OK OK OK OK
     5/8 lambda OK OK OK OK OK
       1 lambda OK OK OK OK OK
     ------------------------------

The NEC code is:

CM
CE
GW 1 9 0 0 -.207 0 0 .207 .02
GW 2 9 0 .25 -.207 0 .25 .207 .02
GS 0 0 1
GE 0
EX 0 1 5 0 1 0
EX 0 2 5 0 0 1
FR 0 9 0 0 280 5
RP 0 1 360 1000 90 0 1 1
EN

It would be very much appreciated if anyone can suggest what is going
wrong here.

Thanking you in advance,

Martin Berger

martin.berger_at_virgin.net
Received on Thu Mar 19 1998 - 10:42:12 EST