NEC-LIST: Modelling slot cylinder with NEC2

I have used NEC2 to calculate the E field patterns of a half wavelength
circumferential slot on a cylinder of circumference equals two wavelengths.
The width of the slot is one tenth of its length. The results given by NEC2
doesn't agree at all with that calculated using analytical equations. Do you
aware of any discrepancy with NEC2 in cases as such?

For an axial slot on a small cylinder (with circumference less than 3/4
wavelength), I managed to obtain good agreement of results between NEC2 and
the analytical one. Again, as I increase the size of the cylinder (with
circumference greater than two wavelengths while keeping the same dimension for
the slot), the results obtained from NEC2 departs from that of calculated using
the analytical solutions.

I have tried different length (one two and three wavelengths ) for the cylinder
as the theoretical solutions assume infinite length. I have also tried with
wire segment of 0.025 and 0.05 wavelength. Yet the results are still incorrect.
I don't understand why.

I have included a simple example of NEC2 codes. The length of the slot is
half a wavelength, cylinder circumference is two wavelengths and the height
of the cylinder is a wavelength. Feel free to comment if there is any error.
Thanks and hope to hear from you soon.

best regards,
Stanley

CM CIRCUMFERENTIAL SLOTTED CYLINDER OF 9 DEGREE SPACING WIRE-WIRE
CE
GW1,20,4.7747,0.,-7.5,4.7747,0.,7.5,.1
GW2,9,4.7159,.74693,-7.5,4.7159,.74693,-.75,.1
GM0,3,0.,0.,9.,0.,0.,0.,2.
GW3,9,4.7159,-.74693,-7.5,4.7159,-.74693,-.75,.1
GM0,3,0.,0.,-9.,0.,0.,0.,3.
GW4,10,4.7159,.74693,0.,4.7159,.74693,7.5,.1
GM0,3,0.,0.,9.,0.,0.,0.,4.
GW5,10,4.7159,-.74693,0.,4.7159,-.74693,7.5,.1
GM0,3,0.,0.,-9.,0.,0.,0.,5.
GW6,20,3.3762,3.3762,-7.5,3.3762,3.3762,7.5,.1
GM0,30,0.,0.,9.,0.,0.,0.,6.
GW7,1,4.7747,0.,-7.5,4.7159,.74693,-7.5,.1
GM0,39,0.,0.,9.,0.,0.,0.,7.
GM0,20,0.,0.,0.,0.,0.,.75,7.
GS0,0,.01
GE0
FR0,0,0,0,2000.
EX0,1,10,0,1.
RP0,1,73,1311,90.,0.,0.,5.
EN
Received on Fri May 02 1997 - 03:14:00 EDT