to calculate the illumination of my dish, I need the radiation field of the patch antenna. According to the discription by G0MJW in Dubus2/2019 the dish was recalculated with sonnet light software. Unfortunately, sonnet does not show neither the -10dB-illumination angle of the feed nor the radiation pattern. There are lot of publications on the patch antenna, but nothing about the radiation. Does anybody know how to calculate the illumination angle of a patch feed with a free available software?