Problem with supernec.

Hi! Pls am workin on the archimedean spiral antenna over an infinite plane. One of the problems I have with supernec is that at some frequencies it dosent generate radiation pattern. Also when i use plane wave excitation, it generates multiples frequencies. i.e lets say i want to simulate from 600mhz to 1200mhz. it brings results for 600 2wice, 700 2wice all d way to 1200mhz.

I also want to understand what plane wave excitation means. the supernec manual dosent really help.

I attached my snec file for the antenna.jus copy in matlab and run in supernnec

tanx

I do not have supernec installed now. but you have just sent your assembly file. you should attach your simulation files to let others see how you have got in trouble.
plane wave excitation is usefull for RCS calculations. when designing an antenna you should excite the antenna with an excited segment (using current or voltage sources)
when you excite an structure with a plane wave you will be able to see how much power is scattered in different directions. in supernec be carefull that the rcs patterns are normalzed to lambda^2

The picture is an example of a frequency that i dont get a radiation pattern. How can I correct it bcos it affects other parameters.

My Output file is quite large like 50MB so I cant upload it