NEC 2 VS "THE REAL WORLD"

I recently designed a 3 element wire (#12) beam for 40 meters, Using
K6STI's NECWIRES implementation NEC2. Segementation used in the NEC
model was on the order of 100 segements/half wave and further
segmentation did not change the results dramatically. Great pains were
then taken to cut the antenna to the precise lengths in the NEC-2 model.
Upon final construction the antenna appears to perform very close to the
model when compared to a reference dipole and vertical. By "performs
very close" I mean that the gian, front to back and 2:1 SWR bandwidths
are all very close to what the model predicts. The only problem I have
is that the antenna is resonant at 6900 khz instead of the "design
frequency" of 7050 khz.

1)Is this 2% error typical and predictable for all (non -loop) very thin
wire elements in NEC-2?

2)Should I reduce all the element lengths by 2% to get to a design that
really does resonate at 7050 khz? (Or I guess I could raise the design
frequency by 2% and do my optimiztions there?).

Comments, personal experience, etc apprecited.

Dave
N0DH/7
dit dit
Received on Fri Jun 14 1996 - 17:13:00 EDT