Marconi: Most generally the nulls and lobes occur when operating the antenna on other bands. EX.: 40 meter tuned Inverted "L" will show a completely different radiation pattern when operated on 20/15/10 meters. Use the 160-meter antenna then model it for operation on other bands and watch how the pattern changes. My "Phased" Dipole array (W8JK/Lazy H variant) is cut for 80 meters, but when using on other bands will certainly show a much different radiation pattern on say 20 meters. Just my thoughts. I am not confirming or denying M0GVZ statements. I just know from that one antenna I use, from personal experience that there are some lobes on other bands that can experience some gain and nulls also when operated on different bands. All the Best Gary I would be interested to see this modeled. The antenna is 125 feet wide (62.5 ft each side) with 34 ft. spacing with an average height above ground 40 ft. The antenna is resonant 200 Ohms/ X=0 at 3.865 MHZ, then fed with 300 Ohm feedline tuned with a PALSTAR BT1500A balanced line tuner. Be interesting to see the radiation pattern say on 40/20/17 meters. The antenna is oriented broadside East/West.