fdsp.nec

zip contains tool for Antenna Modelling with examples

CM Field Day Special (Jun 84 QST), converted with 4nec2 on 29-Mar-06 22:08
CM
CM A personal favorite, the "Field Day Special" has been built
CM on several bands and accounts well for itself from the home
CM QTH as well as on Field Day. It was described in June, 1984
CM QST. The elements are folded dipoles made from twinlead,
CM connected by a half-twisted twinlead "phasing line". The
CM elements are modeled as ordinary dipoles with a diameter
CM equivalent to the effective diameter of the two-conductor
CM twinlead. This is valid since the radiation properties of
CM ordinary and folded dipoles are identical -- only the
CM feedpoint impedance is affected by the "folding" process,
CM and only the pattern is being modeled here. The program
CM used to design the original antenna wasn't entirely
CM accurate so the element currents reported in QST weren't
CM quite correct. The source currents in the model are the
CM currents actually measured on the elements of a Field Day
CM Special built to the dimensions shown in the QST article.
CM This antenna has a respectable gain at low angles, a good
CM f/b ratio, and a broad forward lobe. It's also quite
CM forgiving. Constructed from twinlead, the input SWR is near
CM unity. You can download the program used to design the
CM "Field Day Special" from http://eznec.com.
CM It would be difficult to model this using transmission
CM lines because the elements are both transmission lines and
CM radiators. Another problem is that the insulation makes the
CM radiating portion appear about 3% longer while making the
CM transmission line about 20% longer to the differential
CM transmission line currents.
CE

sy len=16.041
sy dst=8.479

GW 1 11 0 len 40 0 -len 40 6.03675e-3
GW 2 11 -dst len 40 -dst -len 40 6.03675e-3

GS 0 0 0.3048		' All in ft.
GE 0

EX 6 1 6 0 1 0
sy cur=1.017, pha=145	'130.6
EX 6 2 6 0 cur*cos(pha) cur*sin(pha)

GN 2 0 0 0 13 5.e-3
FR 0 1 0 0 14.1 0

EN