## Near Fields (NE, NH)

```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.

```
Notes:
• 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.