Purpose: To reproduce a structure while rotating about the Z-axis to form a complete cylindrical array and to set flags so that symmetry is utilized in the solution. Card: Cols Parameter ---------------- 1- 2 GR 3- 5 I1 6-10 I2 11-20 blank 21-30 blank 31-40 blank 41-50 blank 51-60 blank 61-70 blank 71-80 blank Parameters: Integers (I1) - Tag number increment. (I2) - Total number of times that the structure is to occur in the cylindrical array. Decimal Numbers The decimal number fields are not used.

- The tag increment (I1) is used to avoid duplication of tag numbers in the reproduced structures. In forming a new structure for the array, all valid tags on the previous copy or original structure are incremented by (I1). Tags equal to zero are not incremented.
- The GR card should never be used when there are segments on the Z-axis or crossing the Z-axis since overlapping segments would result.
- The GR card sets flags so the program makes use of cylindrical
symmetry in solving for the currents. If a structure modeled by N
segments has M sections in cylindrical symmetry (formed by a GR card
with I2 equal to M), the number of complex numbers in matrix storage
and the proportionality factors for matrix fill time and matrix
factor time are:
Matrix Fill Factor Storage Time Time ------- ---- ------ No Symmetry N^2 N^2 N^2 M Symmetric Sections (N^2)/M (N^2)/M (N^2)/M

The matrix factor time represents the optimum for a large matrix factored in core. Generally, somewhat longer times will be observed. - If the structure is added to or modified after the GR card in such a
way that cylindrical symmetry is destroyed, the program must be reset
to a no-symmetry condition. In most cases, the program is set by the
geometry routines for the existing symmetry. Operations that auto-
matically reset the symmetry conditions are:
- Addition of a wire by a GW card destroys all symmetry.
- Generation of additional structures by a GM card, with NRPT greater than zero, destroys all symmetry.
- A GM card acting on only part of the structure (having ITS greater than zero) destroys all symmetry.
- A GX or GR card will destroy all previously established symmetry.
- If a structure is rotated about either the X or Y axis by use of a GM card and a ground plane is specified on the GE card, all symmetry will be destroyed. Rotation about the Z-axis or transla- tion will not affect symmetry. If a ground is not specified, symmetry will be unaffected by any rotation or translation by a GM card, unless NRPT or ITS on the GM card is greater than zero.

- Symmetry will also be destroyed if lumped loads are placed on the struc- ture in an unsymmetric manner. In this case, the program is not auto- matically set to a no-symmetry condition but must be set by a data card following the GR card. A GW card with NS blank will set the program to a no-symmetry condition without modifying the structure. The card must specify a nonzero radius, however, to avoid reading a GC card.
- Placement of nonradiating networks or sources does not affect symmetry.
- When symmetry is used in the solution, the number of symmetric sections (I2) is limited by array dimensions. In the demonstration deck, the limit is 16 sections.
- The GR card produces the same effect on the structure as a GM card if I2 on the GR card is equal to (NRPT+1) on the GM card and if ROZ on the GM card is equal to 360/(NRPT+1) degrees. If the GM card is used, however, the program will not be set to take advantage of symmetry.

*This file was last modified on *