CM 4-square array w/feed system, converted with 4nec2 on 29-Mar-06 22:08
CM
CM This model uses EZNEC's transmission line models for the
CM feed system. Note that the lengths aren't anything like
CM you'd expect. This is because the delay in a transmission
CM line isn't equal to its electrical length except in special
CM circumstances -- circumstances which don't occur in most
CM phased arrays. To see where these feedline lengths came
CM from, see "The Simplest Phased Array Feed System . . That
CM Works" in the ARRL Antenna Compendium, Vol. 2.
CM If you do a comparison with the 4Square model, you'll find
CM a little difference. This is because the elements in the
CM 4Square model aren't quite self-resonant and they're not
CM spaced quite exactly a quarter wave apart. (The feed system
CM was designed for those conditions.) If you delete three of
CM the elements and adjust the length of the fourth to make it
CM resonant (zero feedpoint reactance), then change the
CM lengths of all elements to this new length, and you adjust
CM the spacing to exactly 1/4 wavelength, you'll find very
CM good agreement with the 4SQUARE model. This illustrates how
CM touchy this array is.
CM As it stands, the model isn't good for testing the feed
CM system over a range of frequencies. This is because the
CM feedline lengths are specified in degrees, rather than
CM feet. This makes the lines magic, because they keep the
CM same electrical length regardless of frequency. To make a
CM realistic frequency-dependent model, you'd have to specify
CM the transmission line lengths in feet.
CE
sy len=32.75
GW 1 6 0     0     0     0 0     len 0.0625
GW 2 6 0     34.42 0     0 34.42 len 0.0625
GW 3 6 34.42 0     0 34.42 0     len 0.0625
GW 4 6 34.42 34.42 0 34.42 34.42 len 0.0625

GW 5 1 17 0  0.01 17  0.2  0.01 4.16667e-4
GW 6 1 0  17 0.01 0.2 17   0.01 4.16667e-4
GW 7 1 17 17 0.01 17  17.2 0.01 4.16667e-4

GS 0 0 0.3048		' All in ft.
GE 1
TL 5 1 1 1 50 10.4822538
TL 5 1 4 1 50 31.4467613
TL 6 1 2 1 50 10.4822538
TL 6 1 3 1 50 10.4822538
TL 5 1 7 1 75 3.65364789
TL 6 1 7 1 75 20.2260914
EX 6 7 1 0 1 0
GN 3 0 0 0 13 5.e-3
FR 0 1 0 0 7.15 0
EN