A
ANTENNA ENVIRONMENT, 183
ANTENNA INPUT PARAMETERS, 61, 98
drive point impedances in, 100–102
antenna input parameters, 22, 23
antenna monitor readings, 94–100
height for sample loops, 96–97
optimum height for sample loops in, 95–96
six-tower array, day pattern, 155–156
six-tower array, night pattern, 160, 161, 162
tall-tower array, 167
three-tower array, 151
antenna-tuning units (ATUs) drive voltages, 140–141
input impedances, 142
tower base impedances, 141–142
transmission line impedances, 143–144
local and global minima in, 2–4
mathematical synthesis in, 2
nature of NEC-2 and, 1
physical, 2
role of NEC-2 in, 4
ATUs. See antenna-tuning units AUTOEXEC.BAT file, 17
displacement, 41
six-tower array, night pattern, 164
B
in antenna monitor readings, 99–100
current moments and, 66–67, 73–77
direct and induced current, 63–65
drive point impedance and, 101
field ratio calculation and, 67–72
normalized drive, 69–71, 77–78
in system bandwidth analysis, 136, 137–140
base insulators, 107
drive segment radius and, 118–120
modeling by measurement, 116–118
in system bandwidth analysis, 135–136
base loading detuning by, 85–88
Burke, G. J., xiii–xiv, xv, 9–10
C
CALL.NEC file running, 17
CALL_N.NEC, 71
CALL.OUT, 81, 266. See also output files
CALL_1.OUT, 68
Carlier, P., xix
carrier frequency, 134
six-tower array, day pattern, 154–159
six-tower array, night pattern, 160–165
CE command input file, 14, 188
circular polarization, 9
CM command input file, 14, 188
NX and, 174
commands. See also individual commands
program control, 13, 16–17, 212–250
structure geometry command, 189–210
comment commands, 13, 14, 187–188
CM, 14, 188174
common point-matching networks, 146
“Computer Analysis of the Bottom-fed Fan Antenna” (Burke and Poggio), 171
coordinate planes, reflection in, 205–208
coordinate transformation, 195–196
coupling calculation, 212
CP command, 212
Cram, P., xix
current in antenna monitor readings, 97–99
distribution, listing, 6, 95–96
field ratios and, 82
and location output file, 22–23
sinusoidal distribution of, 66
field ratios and, 82
unity drive, calculating, 73–77
cylindrical structures, 9
D
delimiting, 12
types of, 13
data storage for plotting, 128, 238–239
directional antenna adjustment, 1–2
drive point impedance, 100–102
bandwidth analysis and, 138–139
modeling by measurement, 105–120
six-tower array, day pattern, 156
six-tower array, night pattern, 161–164
tall-tower array, 168
drive signal simulation, 148
dummy wires, 101
E
EK command, 213
in modeling by measurement, 109
elliptical polarization, 9
EN command, 214
end of run command, 214
errors, input file, 17
excitation command. See EX command
voltage source modeling with, 29–30, 137
extended thin-wire kernel approximation, 213
F
far-field pattern listings, 81
far-field radiation patterns, plotting, 83–84
field ratios in detuning by skirting, 91–92
local and global minima and, 2–3
six-tower array, night pattern, 164
verifying, 82
folded monopole towers, 32, 129–131
four-wire configurations, 31–32
in bandwidth analysis, 137
frequency in bandwidth analysis, 137
program control command and, 21–22
full power drives, 71
G
GA command, 190
segment and radius taper and, 114–116
in system bandwidth analysis, 136
NX and, 176
geometry command, 13
geometry print control, 197
GF command, 193
GH command, 194
in detuning by skirting, 90, 93–94
NX and, 176
in radiator modeling, 38
stacking sections with, 32, 36–37, 38
input file, 16
GP command, 197
NX and, 176
ground parameters, 177–178, 223–225
GS command, 201
NX and, 176
in detuning by skirting, 93–94
drive wire definition with, 33–34
in network modeling, 56
in system bandwidth analysis, 136
NX and, 176
H
height adjustment, 35
array geometry for, 44
optimum height for antenna monitor reading sample loops, 95–96
for sample loops in antenna monitor readings, 96–97
helix and spiral specification, 194
helix structures, 9
I
IEEE Transactions on Broadcasting (Trueman), 63, 133
impedance. See also drive point impedances ATU input, 142
calculating intermediate data on, 140–141
drive segment radius and, 118–120
matching, 53
modeling by measurement, 105–120
in parallel in networks, 56
phasing network input, 143, 145
self-, 149–151, 154–155, 160, 166, 171–172
shunt, 57
tall-tower array, 167
transmission line input, 143–144
in transmission line modeling, 58
inductance in detuning by base loading, 85–86
in LD command, 52
in modeling by measurement, 107
base loading, 88
normalized drive, 5
six-tower array, day pattern, 158–159
six-tower array, night pattern, 165
structure geometry command, 189–210
unity drive, 5
interaction approximation range, 226
K
KH command, 226
L
current distribution in, 121
in system bandwidth analysis, 134–135
Lawrence Livermore National Laboratories, xv, 9–10
array geometry and, 48
in detuning by skirting, 93
floating-point numbers in, 52
in impedance load modeling, 51–53
NX and, 176
load modeling, 227–229. See also LD command
program control command and, 21–22
shunt impedance, 53
loss modeling, 48
M
mathematical synthesis, in array adjustment, 2
measurement, modeling by, 105–120
drive segment radius in, 118–120
segment number in, 107, 108–111
Morecroft, J. H., 31
N
Naval Ocean Systems Center Technical Document 116
NecDrv2.EXE, 77–78, 260, 265–266
NEC2dxs.xip files, 10
NEC-2 (Numerical Electromagnetics Code version 2), xv, 5–6
nature of, 1
operation of, 11
public domain software with, 5
role of in array adjustment, 4
scope of, 9
software requirements, 7
user-friendliness of, xv
NEC-4 (Numerical Electromagnetics Code version 4), 10
current computation with, 211
network modeling. See also NT command
common applications and, 55–57
common point-matching, 146
drive point impedances in, 100–102
guidelines for, 57
input parameters in, 61
parallel feeds in, 56, 171–173
phasing input impedances in, 144, 145
source and load impedance in, 60–61
voltage transmission between networks in, 140–141
networks drive splitting in, 171–173
next structure command, 173–177, 236
NGF files. See also Numerical Green's Function
reading, 193
writing, 248
current computation with, 211
in bandwidth analysis, 137
in load modeling, 52
in network modeling, 57
in nonradiating network modeling, 53
NX and, 176
Numerical Electromagnetic Code (NEC) — Method of Moments, Part III: User's Guide, 185
Numerical Green's Function, 9, 175–177
NVCOMP.EXE, 38–39, 260, 263–265
detuning by base loading and, 90–91
folded monopoles in, 131
NV.EXE, 38
CE and, 176
Numerical Green's Function and, 175–177
O
antenna input parameters in, 22, 23
antenna monitor readings in, 94–100
condensed, 81
currents and locations in, 22–23
drive point impedances, 100–102
far-field radiation patterns and, 83–84
field ratio verification in, 82
header in, 18
segmentation data in, 18–21, 81
structure specifications for, 18, 19
P
parasitic radiation, comparisons for, 174
pass-through networks, 55
phase local and global minima and, 2–3
phasing network input impedance, 143, 145
phasing networks, 53
Pi-networks, 57
vertical radiation patterns and, 128
power divider input impedances, 143, 145
PQ command, 237
Principles of Radio Communication (Morecroft), 31
program control command, 13, 16–17, 212–250
R
radiation patterns, 24–25, 242–245. See also RP command
detuning unused towers and, 84–94
parasitic, 157–158, 162–163, 174
six-tower array, day pattern, 157–158
six-tower array, night pattern, 162–164
in lattice configurations, 35
reactance physical shunting, 98–99
Reflection Coefficient Approximation (RCA), 182
reflection in coordinate planes, 205–207
ring girth, 37
coding, 34
defining, 33
top loading and, 124
RP. See radiation patterns
array geometry and, 48
current computation with, 211
in plotting far-field radiation patterns, 83–84
S
scaling structure dimensions, 201–204
segmentation data, 81
segment lengths intersection angle of, 28
load and, 52
print control for charge on, 237
in system bandwidth analysis, 136
thick wire vs. thin wire, 108–110
segment numbers, in modeling by measurement, 107, 108–111
self-impedance parallel feeds and, 171–172
six-tower array, day pattern, 154–155
six-tower array, night pattern, 160
tall-tower array, 166
shunt admittances, 59
in modeling by measurement, 107
single-wire configurations, 31
six-tower arrays day pattern, 154–159
skirted towers, 32, 121, 126–131
SM command, 210
Sommerfeld/Norton finite-ground method, 9, 182–183
defining, 33
top loading and, 124
spiral specification, 194
SQR.OUT base current samples and, 97–99
drive point impedances in, 100–102
in plotting far-field radiation patterns, 83–84
SQR_1.OUT, 73
STRUCTURE EXCITATION DATA AT NETWORK CONNECTION POINTS, 60–61
structure geometry command, 189–210
“A Study of AM Tower Base Impedance” (Hatfield), 106–107
Stumpff, G., 38
multiple, 210
system bandwidth analysis, 133–148
base drive voltages in, 136, 137–140
common point-matching networks, 146
drive signal simulation in, 148
low-impedance towers and, 148
parameter smoothing in, 148
system definition for, 133–136
transmission lines in, 148
T
templates, array input file, 48–49
TEMP.NEC, 49
text editing, 17
in bandwidth analysis, 134, 137
TL.NEC, 124
top loading, 32
determining degree of, 123–126
top hat size estimation in, 122–123
tower base impedances, 141–142
flexibility in modeling, 109
new structure creation, 173–177
single-wire, 31
in system bandwidth analysis, 134–136
thick-wire, 30
triangular, 30
two-wire, 32
tower feeds, 53
transmission line modeling, 57–59, 246–247
frequency vs. carrier frequency and, 148
in system bandwidth analysis, 134, 137
Trueman, C. W., 63
twotwr.nec, 181
two-wire configurations, 32
U
current moment calculation, 73–77
unity excitation, 68
V
antenna monitor readings and, 99–100
driving point, calculating, 72–79
load, network, and source of, 57, 58
voltage sources, 52
impedance of drive voltage and, 137–140
W
WG command, 248
wire arc specification, 190
wire structure modeling, 10
WordPad, 81
X
18.117.186.46