Purpose: To request calculation of near electric fields in the vicinity of the antenna (NE) and to request near magnetic fields (NH). Card: Cols Parameter ---------------------- 1- 2 NE or NH 3- 5 I1 NEAR 6-10 I2 NRX 11-15 I3 NRY 16-20 I4 NRZ 21-30 F1 XNR 31-40 F2 YNR 41-50 F3 ZNR 51-60 F4 DXNR 61-70 F5 DYNR 71-80 F6 DZNR Parameters: Integers NEAR (I1) - Coordinate system type. The options are: 0 - rectangular coordinates will be used. 1 - spherical coordinates will be used. Remaining Integers Depend on Coordinate Type a. Rectangular coordinates (NEAR = 0) NRX (I2) - Number of points desired in the X, Y, and NRY (I3) - Z directions respectively. X changes NRZ (I4) - the most rapidly, then Y, ind then Z. The value 1 is assumed for any field left blank. b. Spherical coordinates (NEAR = 1) (I2) - Number of points desired in the r, phi, and theta (I3) - directions, respectively. r changes the most (I4) - rapidly, then phi, and then theta. The value 1 is assumed for any field left blank. Floating Point Fields Their specification depends on the coordinate system chosen. a. Rectangular coordinates (NEAR = 0) XNR (F1) - The (X, Y, Z) coordinate position (F1, F2, YNR (F2) - F3) respectively, in meters of the first ZNR (F3) - field point. DXNR (F4) - Coordinate stepping increment in meters for the DYNR (F5) - X, Y, and Z coordinates (F4, F5, F6), respectively. DZNR (F6) - In stepping, X changes most rapidly, then Y, and then Z. b. Spherical coordinates (NEAR = 1) (F1) - The (r, phi, theta) coordinate position (Fl, F2, F3) (F2) - respectively, of the first field point. r is in (F3) - meters, and phi and theta are in degrees. (F4) - Coordinate stepping increments for r, phi, and theta (F5) - (F4, F5, F6), respectively. The stepping increment (F6) - for r is in meters. and for phi and theta is in degrees.

- When only one frequency is being used, near-field cards may be grouped together in order to calculate fields at points with various coordinate increments. For this case, each card encountered produces an immediate execution of the near-field routine and the results are printed. When automatic frequency stepping is being used [i.e., when the number of frequency steps (NFRQ) on the FR card is greater than one], only one NE or NH card can be used for program control inside the frequency loop. Furthermore, the NE or NH card does not cause an execution in this case. Execution will begin only after a subsequent radiation-pattern card (RP) or execution card (XQ) is encountered (see respective write-ups on both of these cards).
- The time required to calculate the field at one point is equivalent to filling one row of the matrix. Thus, if there are N segments in the structure, the time required to calculate fields at N points is equivalent to the time required to fill an N x N interaction matrix.
- The near electric field is computed by whichever form of the field equations selected for filling the matrix, either the thin-wire approximation or extended thin-wire approximation. At large distances from the structure, the segment currents are treated as infinitesimal current elements.
- If the field calculation point falls within a wire segment, the point is displaced by the radius of that segment in a direction normal to the plane containing each source segment and the vector from that source segment to the observation segment. When the specified field-calculation point is at the center of a segment, this convention is the same as is used in filling the interaction matrix. If the field point is on a segment axis, that segment produces no contribution to the H-field or the radial component of the E-field. If these components are of interest, the field point should be on or outside of the segment surface.

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