Sec. 171.311 - Signal format requirements.

The signals radiated by the MLS must conform to the signal format in which angle guidance functions and data functions are transmitted sequentially on the same C-band frequency. Each function is identified by a unique digital code which initializes the airborne receiver for proper processing. The signal format must meet the following minimum requirements:

(a) Frequency assignment. The ground components (except DME/Marker Beacon) must operate on a single frequency assignment or channel, using time division multiplexing. These components must be capable of operating on any one of the 200 channels spaced 300 KHz apart with center frequencies from 5031.0 MHz to 5090.7 MHz and with channel numbering as shown in Table 1a. The operating radio frequencies of all ground components must not vary by more than 10 KHz from the assigned frequency. Any one transmitter frequency must not vary more than 50 Hz in any one second period. The MLS angle/data and DME equipment must operate on one of the paired channels as shown in Table 1b.

                     Table 1a_Frequency Channel Plan
------------------------------------------------------------------------
                                                               Frequency
                         Channel No.                             (MHz)
------------------------------------------------------------------------
500..........................................................     5031.0
501..........................................................     5031.3
502..........................................................     5031.6
503..........................................................     5031.9
504..........................................................     5032.2
505..........................................................     5032.5
506..........................................................     5032.8
507..........................................................     5033.1
508..........................................................     5033.4
509..........................................................     5033.7
510..........................................................     5034.0
511..........................................................     5034.3
                                * * * * *
598..........................................................     5060.4
599..........................................................     5060.7
600..........................................................     5061.0
601..........................................................     5061.3
                                * * * * *
698..........................................................     5090.4
699..........................................................     5090.7
------------------------------------------------------------------------
                                                                    Table 1b_Channels
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                       Channel pairing                                                              DME parameters
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                           Interrogation                     Reply
                                                                                             -----------------------------------------------------------
                                                                   VHF       MLS                                 Pulse codes
                            DME No.                               freq.     angle    MLS Ch.           ------------------------------             Pulse
                                                                   MHz      freq.      No.      Freq.                 DME/P Mode        Freq.     codes
                                                                             MHz                 MHz      DME/N  --------------------    MHz      μs
                                                                                                          μs   IA μs  FA μs
--------------------------------------------------------------------------------------------------------------------------------------------------------
* 1X..........................................................  ........  ........  ........      1025        12  ........  ........       962        12
** 1Y.........................................................  ........  ........  ........      1025        36  ........  ........      1088        30
* 2X..........................................................  ........  ........  ........      1026        12  ........  ........       963        12
** 2Y.........................................................  ........  ........  ........      1026        36  ........  ........      1089        30
* 3X..........................................................  ........  ........  ........      1027        12  ........  ........       964        12
** 3Y.........................................................  ........  ........  ........      1027        36  ........  ........      1090        30
* 4X..........................................................  ........  ........  ........      1028        12  ........  ........       965        12
** 4Y.........................................................  ........  ........  ........      1028        36  ........  ........      1091        30
* 5X..........................................................  ........  ........  ........      1029        12  ........  ........       966        12
** 5Y.........................................................  ........  ........  ........      1029        36  ........  ........      1092        30
* 6X..........................................................  ........  ........  ........      1030        12  ........  ........       967        12
** 6Y.........................................................  ........  ........  ........      1030        36  ........  ........      1093        30
* 7X..........................................................  ........  ........  ........      1031        12  ........  ........       968        12
** 7Y.........................................................  ........  ........  ........      1031        36  ........  ........      1094        30
* 8X..........................................................  ........  ........  ........      1032        12  ........  ........       969        12
** 8Y.........................................................  ........  ........  ........      1032        36  ........  ........      1095        30
* 9X..........................................................  ........  ........  ........      1033        12  ........  ........       970        12
** 9Y.........................................................  ........  ........  ........      1033        36  ........  ........      1096        30
* 10X.........................................................  ........  ........  ........      1034        12  ........  ........       971        12
** 10Y........................................................  ........  ........  ........      1034        36  ........  ........      1097        30
* 11X.........................................................  ........  ........  ........      1035        12  ........  ........       972        12
** 11Y........................................................  ........  ........  ........      1035        36  ........  ........      1098        30
* 12X.........................................................  ........  ........  ........      1036        12  ........  ........       973        12
** 12Y........................................................  ........  ........  ........      1036        36  ........  ........      1099        30
* 13X.........................................................  ........  ........  ........      1037        12  ........  ........       974        12
** 13Y........................................................  ........  ........  ........      1037        36  ........  ........      1100        30
* 14X.........................................................  ........  ........  ........      1038        12  ........  ........       975        12
** 14Y........................................................  ........  ........  ........      1038        36  ........  ........      1101        30
* 15X.........................................................  ........  ........  ........      1039        12  ........  ........       976        12
** 15Y........................................................  ........  ........  ........      1039        36  ........  ........      1102        30
* 16X.........................................................  ........  ........  ........      1040        12  ........  ........       977        12
** 16Y........................................................  ........  ........  ........      1040        36  ........  ........      1103        30
[dtri]17X.....................................................    108.00  ........  ........      1041        12  ........  ........       978        12
17Y...........................................................    108.05    5043.0       540      1041        36        36        42      1104        30
17Z...........................................................  ........    5043.3       541      1041  ........        21        27      1104        15
18X...........................................................    108.10    5031.0       500      1042        12        12        18       979        12
18W...........................................................  ........    5031.3       501      1042  ........        24        30       979        24
18Y...........................................................    108.15    5043.6       542      1042        36        36        42      1105        30
18Z...........................................................  ........    5043.9       543      1042  ........        21        27      1105        15
19X...........................................................    108.20  ........  ........      1043        12  ........  ........       980        12
19Y...........................................................    108.25    5044.2       544      1043        36        36        42      1106        30
19Z...........................................................  ........    5044.5       545      1043  ........        21        27      1106        15
20X...........................................................    108.30    5031.6       502      1044        12        12        18       981        12
20W...........................................................  ........    5031.9       503      1044  ........        24        30       981        24
20Y...........................................................    108.35    5044.8       546      1044        36        36        42      1107        30
20Z...........................................................  ........    5045.1       547      1044  ........        21        27      1107        15
21X...........................................................    108.40  ........  ........      1045        12  ........  ........       982        12
21Y...........................................................    108.45    5045.4       548      1045        36        36        42      1108        30
21Z...........................................................  ........    5045.7       549      1045  ........        21        27      1108        15
22X...........................................................    108.50    5032.2       504      1046        12        12        18       983        12
22W...........................................................  ........    5032.5       505      1046  ........        24        30       983        24
22Y...........................................................    108.55    5046.0       550      1046        36        36        42      1109        30
22Z...........................................................  ........    5046.3       551      1046  ........        21        27      1109        15
23X...........................................................    108.60  ........  ........      1047        12  ........  ........       984        12
23Y...........................................................    108.65    5046.6       552      1047        36        36        42      1110        30
23Z...........................................................  ........    5046.9       553      1047  ........        21        27      1110        15
24X...........................................................    108.70    5032.8       506      1048        12        12        18       985        12
24W...........................................................  ........    5033.1       507      1048  ........        24        30       985        24
24Y...........................................................    108.75    5047.2       554      1048        36        36        42      1111        30
24Z...........................................................  ........    5047.5       555      1048  ........        21        27      1111        15
25X...........................................................    108.80  ........  ........      1049        12  ........  ........       986        12
25Y...........................................................    108.85    5047.8       556      1049        36        36        42      1112        30
25Z...........................................................  ........    5048.1       557      1049  ........        21        27      1112        15
26X...........................................................    108.90    5033.4       508      1050        12        12        18       987        12
26W...........................................................  ........    5033.7       509      1050  ........        24        30       987        24
26Y...........................................................    108.95    5048.4       558      1050        36        36        42      1113        30
26Z...........................................................  ........    5048.7       559      1050  ........        21        27      1113        15
27X...........................................................    109.00  ........  ........      1051        12  ........  ........       988        12
27Y...........................................................    109.05    5049.0       560      1051        36        36        42      1114        30
27Z...........................................................  ........    5049.3       561      1051  ........        21        27      1114        15
28X...........................................................    109.10    5034.0       510      1052        12        12        18       989        12
28W...........................................................  ........    5034.3       511      1052  ........        24        30       989        24
28Y...........................................................    109.15    5049.6       562      1052        36        36        42      1115        30
28Z...........................................................  ........    5049.9       563      1052  ........        21        27      1115        15
29X...........................................................    109.20  ........  ........      1053        12  ........  ........       990        12
29Y...........................................................    109.25    5050.2       564      1053        36        36        42      1116        30
29Z...........................................................  ........    5050.5       565      1043  ........        21        27      1116        15
30X...........................................................    109.30    5034.6       512      1054        12        12        18       991        12
30W...........................................................  ........    5034.9       513      1054  ........        24        30       991        24
30Y...........................................................    109.35    5050.8       566      1054        36        36        42      1117        30
30Z...........................................................  ........    5051.1       567      1054  ........        21        27      1117        15
31X...........................................................    109.40  ........  ........      1055        12  ........  ........       992        12
31Y...........................................................    109.45    5051.4       568      1055        36        36        42      1118        30
31Z...........................................................  ........    5051.7       569      1055  ........        21        27      1118        15
32X...........................................................    109.50    5035.2       514      1056        12        12        18       993        12
32W...........................................................  ........    5035.5       515      1056  ........        24        30       993        24
32Y...........................................................    109.55    5052.0       570      1056        36        36        42      1119        30
32Z...........................................................  ........    5052.3       571      1056  ........        21        27      1119        15
33X...........................................................    109.60  ........  ........      1057        12  ........  ........       994        12
33Y...........................................................    109.65    5052.6       572      1057        36        36        42      1120        30
33Z...........................................................  ........    5052.9       573      1057  ........        21        27      1120        15
34X...........................................................    109.70    5035.8       516      1058        12        12        18       995        12
34W...........................................................  ........    5036.1       517      1058  ........        24        30       995        24
34Y...........................................................    109.75    5053.2       574      1058        36        36        42      1121        30
34Z...........................................................  ........    5053.5       575      1058  ........        21        27      1121        15
35X...........................................................    109.80  ........  ........      1059        12  ........  ........       996        12
35Y...........................................................    109.85    5053.8       576      1059        36        36        42      1122        30
35Z...........................................................  ........    5054.1       577      1059  ........        21        27      1122        15
36X...........................................................    109.90    5036.4       518      1060        12        12        18       997        12
36W...........................................................  ........    5036.7       519      1060  ........        24        30       997        24
36Y...........................................................    109.95    5054.4       578      1060        36        36        42      1123        30
36Z...........................................................  ........    5054.7       579      1060  ........        21        27      1123        15
37X...........................................................    110.00  ........  ........      1061        12  ........  ........       998        12
37Y...........................................................    110.05    5055.0       580      1061        36        36        42      1124        30
37Z...........................................................  ........    5055.3       581      1061  ........        21        27      1124        15
38X...........................................................    110.10    5037.0       520      1062        12        12        18       999        12
38W...........................................................  ........    5037.3       521      1062  ........        24        30       999        24
38Y...........................................................    110.15    5055.6       582      1062        36        36        42      1125        30
38Z...........................................................  ........    5055.9       583      1062  ........        21        27      1125        15
39X...........................................................    110.20  ........  ........      1063        12  ........  ........      1000        12
39Y...........................................................    110.25    5056.2       584      1063        36        36        42      1126        30
39Z...........................................................  ........    5056.5       585      1063  ........        21        27      1126        15
40X...........................................................    110.30    5037.6       522      1064        12        12        18      1001        12
40W...........................................................  ........    5037.9       523      1064  ........        24        30      1001        24
40Y...........................................................    110.35    5056.8       586      1064        36        36        42      1127        30
40Z...........................................................  ........    5057.1       587      1064  ........        21        27      1127        15
41X...........................................................    110.40  ........  ........      1065        12  ........  ........      1002        12
41Y...........................................................    110.45    5057.4       588      1065        36        36        42      1128        30
41Z...........................................................  ........    5057.7       589      1065  ........        21        27      1128        15
42X...........................................................    110.50    5038.2       524      1066        12        12        18      1003        12
42W...........................................................  ........    5038.5       525      1066  ........        24        30      1003        24
42Y...........................................................    110.55    5058.0       590      1066        36        36        42      1129        30
42Z...........................................................  ........    5058.3       591      1066  ........        21        27      1129        15
43X...........................................................    110.60  ........  ........      1067        12  ........  ........      1004        12
43Y...........................................................    110.65    5058.6       592      1067        36        36        42      1130        30
43Z...........................................................  ........    5058.9       593      1067  ........        21        27      1130        15
44X...........................................................    110.70    5038.8       526      1068        12        12        18      1005        12
44W...........................................................  ........    5039.1       527      1068  ........        24        30      1005        24
44Y...........................................................    110.75    5059.2       594      1068        36        36        42      1131        30
44Z...........................................................  ........    5059.5       595      1068  ........        21        27      1131        15
45X...........................................................    110.80  ........  ........      1069        12  ........  ........      1006        12
45Y...........................................................    110.85    5059.8       596      1069        36        36        42      1132        30
45Z...........................................................  ........    5060.1       597      1069  ........        21        27      1132        15
46X...........................................................    110.90    5039.4       528      1070        12        12        18      1007        12
46W...........................................................  ........    5039.7       529      1070  ........        24        30      1007        24
46Y...........................................................    110.95    5060.4       598      1070        36        36        42      1133        30
46Z...........................................................  ........    5060.7       599      1070  ........        21        27      1133        15
47X...........................................................    111.00  ........  ........      1071        12  ........  ........      1008        12
47Y...........................................................    111.05    5061.0       600      1071        36        36        42      1134        30
47Z...........................................................  ........    5061.3       601      1071  ........        21        27      1134        15
48X...........................................................    111.10    5040.0       530      1072        12        12        18      1009        12
48W...........................................................  ........    5040.3       531      1072  ........        24        30      1009        24
48Y...........................................................    111.15    5061.6       602      1072        36        36        42      1135        30
48Z...........................................................  ........    5061.9       603      1072  ........        21        27      1135        15
49X...........................................................    111.20  ........  ........      1073        12  ........  ........      1010        12
49Y...........................................................    111.25    5062.2       604      1073        36        36        42      1136        30
49Z...........................................................  ........    5062.5       605      1073  ........        21        27      1136        15
50X...........................................................    111.30    5040.6       532      1074        12        12        18      1011        12
50W...........................................................  ........    5040.9       533      1074  ........        24        30      1011        24
50Y...........................................................    111.35    5062.8       606      1074        36        36        42      1137        30
50Z...........................................................  ........    5063.1       607      1074  ........        21        27      1137        15
51X...........................................................    111.40  ........  ........      1075        12  ........  ........      1012        12
51Y...........................................................    111.45    5063.4       608      1075        36        36        42      1138        30
51Z...........................................................  ........    5063.7       609      1075  ........        21        27      1138        15
52X...........................................................    111.50    5041.2       534      1076        12        12        18      1013        12
52W...........................................................  ........    5041.5       535      1076  ........        24        30      1013        24
52Y...........................................................    111.55    5064.0       610      1076        36        36        42      1139        30
52Z...........................................................  ........    5064.3       611      1076  ........        21        27      1139        15
53X...........................................................    111.60  ........  ........      1077        12  ........  ........      1014        12
53Y...........................................................    111.65    5064.6       612      1077        36        36        42      1140        30
53Z...........................................................  ........    5064.9       613      1077  ........        21        27      1140        15
54X...........................................................    111.70    5041.8       536      1078        12        12        18      1015        12
54W...........................................................  ........    5042.1       537      1078  ........        24        30      1015        24
54Y...........................................................    111.75    5065.2       614      1078        36        36        42      1141        30
54Z...........................................................  ........    5065.5       615      1078  ........        21        27      1141        15
55X...........................................................    111.80  ........  ........      1079        12  ........  ........      1016        12
55Y...........................................................    111.85    5065.8       616      1079        36        36        42      1142        30
55Z...........................................................  ........    5066.1       617      1079  ........        21        27      1142        15
56X...........................................................    111.90    5042.4       538      1080        12        12        18      1017        12
56W...........................................................  ........    5042.7       539      1080  ........        24        30      1017        24
56Y...........................................................    111.95    5066.4       618      1080        36        36        42      1143        30
56Z...........................................................  ........    5066.7       619      1080  ........        21        27      1143        15
57X...........................................................    112.00  ........  ........      1081        12  ........  ........      1018        12
57Y...........................................................    112.05  ........  ........      1081        36  ........  ........      1144        30
58X...........................................................    112.10  ........  ........      1082        12  ........  ........      1019        12
58Y...........................................................    112.15  ........  ........      1082        36  ........  ........      1145        30
59X...........................................................    112.20  ........  ........      1083        12  ........  ........      1020        12
59Y...........................................................    122.25  ........  ........      1083        36  ........  ........      1146        30
** 60X........................................................  ........  ........  ........      1084        12  ........  ........      1021        12
** 60Y........................................................  ........  ........  ........      1084        36  ........  ........      1147        30
** 61X........................................................  ........  ........  ........      1085        12  ........  ........      1022        12
** 61Y........................................................  ........  ........  ........      1085        36  ........  ........      1148        30
** 62X........................................................  ........  ........  ........      1086        12  ........  ........      1023        12
** 62Y........................................................  ........  ........  ........      1086        36  ........  ........      1149        30
** 63X........................................................  ........  ........  ........      1037        12  ........  ........      1024        12
** 63Y........................................................  ........  ........  ........      1087        36  ........  ........      1150        30
** 64X........................................................  ........  ........  ........      1088        12  ........  ........      1151        12
** 64Y........................................................  ........  ........  ........      1088        36  ........  ........      1025        30
** 65X........................................................  ........  ........  ........      1089        12  ........  ........      1152        12
** 65Y........................................................  ........  ........  ........      1089        36  ........  ........      1026        30
** 66X........................................................  ........  ........  ........      1090        12  ........  ........      1153        12
** 66Y........................................................  ........  ........  ........      1090        36  ........  ........      1027        30
** 67X........................................................  ........  ........  ........      1091        12  ........  ........      1154        12
** 67Y........................................................  ........  ........  ........      1091        36  ........  ........      1028        30
** 68X........................................................  ........  ........  ........      1092        12  ........  ........      1155        12
** 68Y........................................................  ........  ........  ........      1092        36  ........  ........      1029        30
** 69X........................................................  ........  ........  ........      1093        12  ........  ........      1156        12
** 69Y........................................................  ........  ........  ........      1093        36  ........  ........      1030        30
70X...........................................................    112.30  ........  ........      1094        12  ........  ........      1157        12
** 70Y........................................................    112.35  ........  ........      1094        36  ........  ........      1031        30
71X...........................................................    112.40  ........  ........      1095        12  ........  ........      1158        12
** 71Y........................................................    112.45  ........  ........      1095        36  ........  ........      1032        30
72X...........................................................    112.50  ........  ........      1096        12  ........  ........      1159        12
** 72Y........................................................    112.55  ........  ........      1096        36  ........  ........      1033        30
73X...........................................................    112.60  ........  ........      1097        12  ........  ........      1160        12
** 73Y........................................................    112.65  ........  ........      1097        36  ........  ........      1034        30
74X...........................................................    112.70  ........  ........      1098        12  ........  ........      1161        12
** 74Y........................................................    112.75  ........  ........      1098        36  ........  ........      1035        30
75X...........................................................    112.80  ........  ........      1099        12  ........  ........      1162        12
** 75Y........................................................    112.85  ........  ........      1099        36  ........  ........      1036        30
76X...........................................................    112.90  ........  ........      1100        12  ........  ........      1163        12
** 76Y........................................................    112.95  ........  ........      1100        36  ........  ........      1037        30
77X...........................................................    113.00  ........  ........      1101        12  ........  ........      1164        12
** 77Y........................................................    113.05  ........  ........      1101        36  ........  ........      1038        30
78X...........................................................    113.10  ........  ........      1102        12  ........  ........      1165        12
** 78Y........................................................    113.15  ........  ........      1102        36  ........  ........      1039        30
79X...........................................................    113.20  ........  ........      1103        12  ........  ........      1166        12
** 79Y........................................................    113.25  ........  ........      1103        36  ........  ........      1040        30
80X...........................................................    113.30  ........  ........      1104        12  ........  ........      1167        12
80Y...........................................................    113.35    5067.0       620      1104        36        36        42      1041        30
80Z...........................................................  ........    5067.3       621      1104  ........        21        27      1041        15
81X...........................................................    113.40  ........  ........      1105        12  ........  ........      1168        12
81Y...........................................................    113.45    5067.6       622      1105        36        36        42      1042        30
81Z...........................................................  ........    5067.9       623      1005  ........        21        27      1042        15
82X...........................................................    113.50  ........  ........      1106        12  ........  ........      1169        12
82Y...........................................................    113.55    5068.2       624      1106        36        36        42      1043        30
82Z...........................................................  ........    5068.5       625      1106  ........        21        27      1043        15
83X...........................................................    113.60  ........  ........      1107        12  ........  ........      1170        12
83Y...........................................................    113.65    5068.8       626      1107        36        36        42      1044        30
83Z...........................................................  ........    5069.1       627      1107  ........        21        27      1044        15
84X...........................................................    113.70  ........  ........      1108        12  ........  ........      1171        12
84Y...........................................................    113.75    5069.4       628      1108        36        36        42      1045        30
84Z...........................................................  ........    6069.7       629      1108  ........        21        27      1045        15
85X...........................................................    113.80  ........  ........      1109        12  ........  ........      1172        12
85Y...........................................................    113.85    5070.0       630      1109        36        36        42      1046        30
85Z...........................................................  ........    5070.3       631      1109  ........        21        27      1046        15
86X...........................................................    113.90  ........  ........      1110        12  ........  ........      1173        12
86Y...........................................................    113.95    5070.6       632      1110        36        36        42      1047        30
86Z...........................................................  ........    5070.9       633      1110  ........        21        27      1047        15
87X...........................................................    114.00  ........  ........      1111        12  ........  ........      1174        12
87Y...........................................................    114.05    5071.2       634      1111        36        36        42      1048        30
87Z...........................................................  ........    5071.5       635      1111  ........        21        27      1048        15
88X...........................................................    114.10  ........  ........      1112        12  ........  ........      1175        12
88Y...........................................................    114.15    5071.8       636      1112        36        36        42      1049        30
88Z...........................................................  ........    5072.1       637      1112  ........        21        27      1049        15
89X...........................................................    114.20  ........  ........      1113        12  ........  ........      1176        12
89Y...........................................................    114.25    5072.4       638      1113        36        36        42      1050        30
89Z...........................................................  ........    5072.7       639      1113  ........        21        27      1050        15
90X...........................................................    114.30  ........  ........      1114        12  ........  ........      1177        12
90Y...........................................................    114.35    5073.0       640      1114        36        36        42      1051        30
90Z...........................................................  ........    5073.3       641      1114  ........        21        27      1051        15
91X...........................................................    114.40  ........  ........      1115        12  ........  ........      1178        12
91Y...........................................................    114.45    5073.6       642      1115        36        36        42      1052        30
91Z...........................................................  ........    5073.9       643      1115  ........        21        27      1052        15
92X...........................................................    114.50  ........  ........      1116        12  ........  ........      1179        12
92Y...........................................................    114.55    5074.2       644      1116        36        36        42      1053        30
92Z...........................................................  ........    5074.5       645      1116  ........        21        27      1053        15
93X...........................................................    114.60  ........  ........      1117        12  ........  ........      1180        12
93Y...........................................................    114.65    5074.8       646      1117        36        36        42      1054        30
93Z...........................................................  ........    5075.1       647      1117  ........        21        27      1054        15
94X...........................................................    114.70  ........  ........      1118        12  ........  ........      1181        12
94Y...........................................................    114.75    5075.4       648      1118        36        36        42      1055        30
94Z...........................................................  ........    5075.7       649      1118  ........        21        27      1055        15
95X...........................................................    114.80  ........  ........      1119        12  ........  ........      1182        12
95Y...........................................................    114.85    5076.0       650      1119        36        36        42      1056        30
95Z...........................................................  ........    5076.3       651      1119  ........        21        27      1056        15
96X...........................................................    114.90  ........  ........      1120        12  ........  ........      1183        12
96Y...........................................................    114.95    5076.6       652      1120        36        36        42      1057        30
96Z...........................................................  ........    5076.9       653      1120  ........        21        27      1057        15
97X...........................................................    115.00  ........  ........      1121        12  ........  ........      1184        12
97Y...........................................................    115.05    5077.2       654      1121        36        36        42      1058        30
97Z...........................................................  ........    5077.5       655      1121  ........        21        27      1058        15
98X...........................................................    115.10  ........  ........      1122        12  ........  ........      1185        12
98Y...........................................................    115.15    5077.8       656      1122        36        36        42      1059        30
98Z...........................................................  ........    5078.1       657      1122  ........        21        27      1059        15
99X...........................................................    115.20  ........  ........      1123        12  ........  ........      1186        12
99Y...........................................................    115.25    5078.4       658      1123        36        36        42      1060        30
99Z...........................................................  ........    5078.7       659      1123  ........        21        27      1060        15
100X..........................................................    115.30  ........  ........      1124        12  ........  ........      1187        12
100Y..........................................................    115.35    5079.0       660      1124        36        36        42      1061        30
100Z..........................................................  ........    5079.3       661      1124  ........        21        27      1061        15
101X..........................................................    115.40  ........  ........      1125        12  ........  ........      1188        12
101Y..........................................................    115.45    5079.6       662      1125        36        36        42      1062        30
101Z..........................................................  ........    5079.9       663      1125  ........        21        27      1062        15
102X..........................................................    115.50  ........  ........      1126        12  ........  ........      1189        12
102Y..........................................................    115.55    5080.2       664      1126        36        36        42      1063        30
102Z..........................................................  ........    5080.5       665      1126  ........        21        27      1063        15
103X..........................................................    115.60  ........  ........      1127        12  ........  ........      1190        12
103Y..........................................................    115.65    5080.B       666      1127        36        36        42      1064        30
103Z..........................................................  ........    5081.1       667      1127  ........        21        27      1064        19
104X..........................................................    115.70  ........  ........      1128        12  ........  ........      1191        12
104Y..........................................................    115.75    5081.4       668      1128        36        36        42      1065        30
104Z..........................................................  ........    5081.7       669      1128  ........        21        27      1065        19
105X..........................................................    115.80  ........  ........      1129        12  ........  ........      1192        12
105Y..........................................................    115.85    5082.0       670      1129        36        36        42      1066        30
105Z..........................................................  ........    5082.3       671      1129  ........        21        27      1066        15
106X..........................................................    115.90  ........  ........      1130        12  ........  ........      1193        12
106Y..........................................................    115.95    5082.6       672      1130        36        36        42      1067        30
106Z..........................................................  ........    5082.9       673      1130  ........        21        27      1067        15
107X..........................................................    116.00  ........  ........      1131        12  ........  ........      1194        12
107Y..........................................................    116.05    5083.2       674      1131        36        36        42      1068        30
107Z..........................................................  ........    5083.5       675      1131  ........        21        27      1068        15
108X..........................................................    116.10       508  ........      1132        12  ........  ........      1195        12
108Y..........................................................    116.15    5083.8       676      1132        36        36        42      1069        30
108Z..........................................................  ........    5084.1       677      1132  ........        21        27      1069        15
109X..........................................................    116.20  ........  ........      1133        12  ........  ........      1196        12
109Y..........................................................    116.25    5084.4       678      1133        36        36        42      1070        30
109Z..........................................................  ........    5084.7       679      1133  ........        21        27      1070        15
110X..........................................................    116.30  ........  ........      1134        12  ........  ........      1197        12
110Y..........................................................    116.35    5085.0       680      1134        36        36        42      1071        30
110Z..........................................................  ........    5085.3       681      1134  ........        21        27      1071        15
111X..........................................................    116.40  ........  ........      1135        12  ........  ........      1198        12
111Y..........................................................    116.45    5086.6       682      1135        36        36        42      1072        30
111Z..........................................................  ........    5085.9       683      1135  ........        21        27      1072        15
112X..........................................................    116.50  ........  ........      1136        12  ........  ........      1199        12
112Y..........................................................    116.55    5086.2       684      1136        36        36        42      1073        30
112Z..........................................................  ........    5086.5       685      1136  ........        21        27      1073        15
113X..........................................................    116.60  ........  ........      1137        12  ........  ........      1200        12
113Y..........................................................    116.65    5086.8       686      1137        36        36        42      1074        30
113Z..........................................................  ........    5087.1       687      1137  ........        21        27      1074        15
114X..........................................................    116.70  ........  ........      1138        12  ........  ........      1201        12
114Y..........................................................    116.75    5087.4       688      1138        36        36        42      1075        30
114Z..........................................................  ........    5087.7       689      1138  ........        21        27      1075        15
115X..........................................................    116.80  ........  ........      1139        12  ........  ........      1202        12
115Y..........................................................    116.85    5088.0       690      1139        36        36        42      1076        30
115Z..........................................................  ........    5088.3       691      1139  ........        21        27      1076        15
116X..........................................................    116.90  ........  ........      1140        12  ........  ........      1203        12
116Y..........................................................    116.95    5088.6       692      1140        36        36        42      1077        30
116Z..........................................................  ........    5088.9       693      1140  ........        21        27      1077        15
117X..........................................................    117.00  ........  ........      1141        12  ........  ........      1204        12
117Y..........................................................    117.05    5089.2       694      1141        36        36        42      1078        30
117Z..........................................................  ........    5089.5       695      1141  ........        21        27      1078        15
118X..........................................................    117.10  ........  ........      1142        12  ........  ........      12.5        12
118Y..........................................................    117.15    5089.8       696      1142        36        36        42      1079        30
118Z..........................................................  ........    5090.1       697      1142  ........        21        27      1079        12
119X..........................................................    117.20  ........  ........      1143        12  ........  ........      1206        12
119Y..........................................................    117.25    5090.4       698      1143        36        36        42      1080        30
119Z..........................................................  ........    5090.7       699      1143  ........        21        27      1080        15
120X..........................................................    117.30  ........  ........      1144        12  ........  ........      1207        12
120Y..........................................................    117.35  ........  ........      1144        36  ........  ........      1081        30
121X..........................................................    117.40  ........  ........      1145        12  ........  ........      1208        12
121Y..........................................................    117.45  ........  ........      1145        36  ........  ........      1082        30
122X..........................................................    117.50  ........  ........      1146        12  ........  ........      1209        12
122Y..........................................................    117.55  ........  ........      1146        36  ........  ........      1083        30
123X..........................................................    117.60  ........  ........      1147        12  ........  ........      1210        12
123Y..........................................................    117.65  ........  ........      1147        36  ........  ........      1084        30
124X..........................................................    117.70  ........  ........      1148        12  ........  ........      1211        12
** 124Y.......................................................    117.75  ........  ........      1148        36  ........  ........      1085        30
125X..........................................................    117.80  ........  ........      1149        12  ........  ........      1212        12
** 125Y.......................................................    117.85  ........  ........      1149        36  ........  ........      1086        30
126X..........................................................    117.90  ........  ........      1150        12  ........  ........      1213        12
** 126Y.......................................................    117.95  ........  ........      1150        36  ........  ........      1087        30
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
* These channels are reserved exclusively for national allotments.
** These channels may be used for national allotment on a secondary basis. The primary reason for reserving these channels is to provide protection for
  the secondary Surveillance Radar (SSR) system.
[dtri] 108.0 MHz is not scheduled for assignment to ILS service. The associated DME operating channel No. 17X may be assigned to the emergency service.

(b) Polarization. (1) The radio frequency emissions from all ground equipment must be nominally vertically polarized. Any horizontally polarized radio frequency emission component from the ground equipment must not have incorrectly coded angle information such that the limits specified in paragraphs (b) (2) and (3) of this section are exceeded.

(2) Rotation of the receiving antenna thirty degrees from the vertically polarized position must not cause the path following error to exceed the allowed error at that location.

(c) Modulation requirements. Each function transmitter must be capable of DPSK and continuous wave (CW) modulations of the RF carrier which have the following characteristics.

(1) DPSK. The DPSK signal must have the following characteristics:

bit rate         15.625 KHz
bit length       64 microseconds
logic ``0''      no phase transition
logic ``1''      phase transition
  phase          less than 10 microseconds
 transition
phase tolerance   10 degrees

The phase shall advance (or retard) monotonically throughout the transition region. Amplitude modulation during the phase transition period shall not be used.

(2) CW. The CW pulse transmissions and the CW angle transmissions as may be required in the signal format of any function must have characteristics such that the requirements of paragraph (d) of this section are met.

(d) Radio frequency signal spectrum. The transmitted signal must be such that during the transmission time, the mean power density above a height of 600 meters (2000 feet) does not exceed −100.5 dBW/m 2 for angle guidance and −95.5 dBW/m 2 for data, as measured in a 150 KHz bandwidth centered at a frequency of 840 KHz or more from the assigned frequency.

(e) Synchronization. Synchronization between the azimuth and elevation components is required and, in split-site configurations, would normally be accomplished by landline interconnections. Synchronization monitoring must be provided to preclude function overlap.

(f) Transmission rates. Angle guidance and data signals must be transmitted at the following average repetition rates:

------------------------------------------------------------------------
                                                                Average
                           Function                            data rate
                                                                (Hertz)
------------------------------------------------------------------------
Approach Azimuth.............................................  130
                                                                      .5
High Rate Approach Azimuth...................................        \1\
                                                               391
                                                                      .5
Approach Elevation...........................................  391
                                                                      .5
Back Azimuth.................................................  6.5
                                                                    0.25
Basic Data...................................................      (\2\)
Auxiliary Data...............................................      (\3\)
------------------------------------------------------------------------
\1\ The higher rate is recommended for azimuth scanning antennas with
  beamwidths greater than two degrees. It should be noted that the time
  available in the signal format for additional functions is limited
  when the higher rate is used.
\2\ Refer to Table 8a.
\3\ Refer to Table 8c.

(g) Transmission sequences. Sequences of angle transmissions which will generate the required repetition rates are shown in Figures 2 and 3.




 

(h) TDM cycle. The time periods between angle transmission sequences must be varied so that exact repetitions do not occur within periods of less than 0.5 second in order to protect against synchronous interference. One such combination of sequences is shown in Figure 4 which forms a full multiplex cycle. Data may be transmitted during suitable open times within or between the sequences.

(i) Function Formats (General). Each angle function must contain the following elements: a preamble; sector signals; and a TO and FRO angle scan organized as shown in Figure 5a. Each data function must contain a preamble and a data transmission period organized as shown in Figure 5b.

(1) Preamble format. The transmitted angle and date functions must use the preamble format shown in Figure 6. This format consists of a carrier acquisition period of unmodulated CW transmission followed by a receiver synchronization code and a function identification code. The preamble timing must be in accordance with Table 2.

 

(i) Digital codes. The coding used in the preamble for receiver synchronization is a Barker code logic 11101. The time of the last phase transition midpoint in the code shall be the receiver reference time (see Table 2). The function identification codes must be as shown in Table 3. The last two bits (I11 and I12) of the code are parity bits obeying the equations:

I6+I7+I8+I9+I10+I11=Even

I6+I8+I10+I12=Even
 

(ii) Data modulation. The digital code portions of the preamble must be DPSK modulated in accordance with 171.311(c)(1) and must be transmitted throughout the function coverage volume.

(2) Angle function formats. The timing of the angle transmissions must be in accordance with Tables 4a, 4b, and 5. The actual timing of the TO and FRO scans must be as required to meet the accuracy requirements of 171.313 and 171.317.

(i) Preamble. Must be in accordance with requirements of 171.311(i)(1).

                       Table 2_Preamble Timing \1\
------------------------------------------------------------------------
                                                 Event time slot begins
                                                           at_
                                               -------------------------
                                                 15.625
                     Event                         kHz
                                                  clock        Time
                                                  pulse   (milliseconds)
                                                (number)
------------------------------------------------------------------------
Carrier acquisition:
  (CW transmission)...........................         0         0
Receiver reference time code:
  I[INF]1[/INF]=1.............................        13         0.832
  I[INF]2[/INF]=1.............................        14         0.896
  I[INF]3[/INF]=1.............................        15         0.960
  I[INF]4[/INF]=0.............................        16         1.024
  I[INF]5[/INF]=1.............................        17     \2\ 1.088
Function identification:
  I[INF]6[/INF]...............................        18         1.152
  I[INF]7[/INF]...............................        19         1.216
  I[INF]8[/INF]...............................        20         1.280
  I[INF]9[/INF]...............................        21         1.344
  I[INF]10[/INF] (see table 1)................        22         1.408
  I[INF]11[/INF]..............................        23         1.472
  I[INF]12[/INF]..............................        24         1.536
  END PREAMBLE................................        25         1.600
------------------------------------------------------------------------
\1\ Applies to all functions transmitted.
\2\ Reference time for receiver synchronization for all function timing.
                                      Table 3_Function Identification Codes
----------------------------------------------------------------------------------------------------------------
                                                                       Code
                                 -------------------------------------------------------------------------------
            Function              I[INF]6[/  I[INF]7[/  I[INF]8[/  I[INF]9[/  I[INF]10[/  I[INF]11[/  I[INF]12[/
                                     INF]       INF]       INF]       INF]       INF]        INF]        INF]
----------------------------------------------------------------------------------------------------------------
Approach azimuth................       0          0          1          1          0           0           1
High rate approach azimuth......       0          0          1          0          1           0           0
Approach elevation..............       1          1          0          0          0           0           1
Back azimuth....................       1          0          0          1          0           0           1
Basic data 1....................       0          1          0          1          0           0           0
Basic data 2....................       0          1          1          1          1           0           0
Basic data 3....................       1          0          1          0          0           0           0
Basic data 4....................       1          0          0          0          1           0           0
Basic data 5....................       1          1          0          1          1           0           0
Dasic data 6....................       0          0          0          1          1           0           1
Auxiliary data A................       1          1          1          0          0           1           0
Auxiliary data B................       1          0          1          0          1           1           1
Auxiliary data C................       1          1          1          1          0           0           0
----------------------------------------------------------------------------------------------------------------

(ii) Sector signals. In all azimuth formats, sector signals must be transmitted to provide Morse Code identification, airborne antenna selection, and system test signals. These signals are not required in the elevation formats. In addition, if the signal from an installed ground component results in a valid indication in an area where no valid guidance should exist, OCI signals must be radiated as provided for in the signal format (see Tables 4a, 4b, and 5). The sector signals are defined as follows:

(A) Morse Code. DPSK transmissions that will permit Morse Code facility identification in the aircraft by a four letter code starting with the letter "M" must be included in all azimuth functions. They must be transmitted and repeated at approximately equal intervals, not less than six times per minute, during which time the ground subsystem is available for operational use. When the transmissions of the ground subsystem are not available, the identification signal must be suppressed. The audible tone in the aircraft is started by setting the Morse Code bit to logic "1" and stopped by a logic "0" (see Tables 4a and 4b). The identification code characteristics must conform to the following: the dot must be between 0.13 and 0.16 second in duration, and the dash between 0.39 and 0.48 second. The duration between dots and/or dashes must be one dot plus or minus 10%. The duration between characters (letters) must not be less than three dots. When back azimuth is provided, the code shall be transmitted by the approach azimuth and back azimuth within plus or minus 0.08 seconds.

(B) Airborne antenna selection. A signal for airborne antenna selection shall be transmitted as a "zero" DPSK signal lasting for a six-bit period (see Tables 4a and 4b).

                Table 4a_Approach Azimuth Function timing
------------------------------------------------------------------------
                                                 Event time slot begins
                                                           at_
                                               -------------------------
                                                 15.625
                     Event                         kHz
                                                  clock        Time
                                                  pulse   (milliseconds)
                                                (number)
------------------------------------------------------------------------
Preamble......................................         0         0
Morse code....................................        25         1.600
Antenna select................................        26         1.664
Rear OCI......................................        32         2.048
Left OCI......................................        34         2.176
Right OCI.....................................        36         2.304
To test.......................................        38         2.432
To scan \1\...................................        40         2.560
Pause.........................................  ........         8.760
Midscan point.................................  ........         9.060
FRO scan \1\..................................  ........         9.360
FRO test......................................  ........        15.560
End Function (Airborne).......................  ........        15.688
End guard time; end function (ground).........  ........        15.900
------------------------------------------------------------------------
 AA\1\The actual commencement and completion of the TO and the FRO scan
  transmissions are dependent on the amount of proportional guidance
  provided. The time slots provided shall accommodate a maximum scan of
  plus or minus 62.0 degrees. Scan timing shall be compatible with
  accuracy requirements.
  Table 4b_High Rate Approach Azimuth and Back Azimuth Function Timing
------------------------------------------------------------------------
                                                 Event time slot begins
                                                           at_
                                               -------------------------
                                                 15.625
                     Event                         kHz
                                                  clock        Time
                                                  pulse   (milliseconds)
                                                (number)
------------------------------------------------------------------------
Preamble......................................         0         0
Morse Code....................................        25         1.600
Antenna select................................        26         1.664
Rear OCI......................................        32         2.048
Left OCI......................................        34         2.176
Right OCI.....................................        36         2.304
To test.......................................        38         2.432
To scan \1\...................................        40         2.560
Pause.........................................  ........         6.760
Midscan point.................................  ........         7.060
FRO scan \1\..................................  ........         7.360
FRO test pulse................................  ........        11.560
End function (airborne).......................  ........        11.688
End guard time; end function (ground).........  ........        11.900
------------------------------------------------------------------------
\1\ The actual commencement and completion of the TO and the FRO scan
  transmissions are dependent on the amount of proportional guidance
  provided. The time slots provided will accommodate a maximum scan of
  plus or minus 42.0 degrees. Scan timing shall be compatible with
  accuracy requirements.

(C) OCI. Where OCI pulses are used, they must be: (1) greater than any guidance signal in the OCI sector; (2) at least 5 dB less than the level of the scanning beam within the proportional guidance sector; and (3) for azimuth functions with clearance signals, at least 5 dB less than the level of the left (right) clearance pulses within the left (right) clearance sector.

               Table 5_Approach Elevation Function Timing
------------------------------------------------------------------------
                                                 Event time slot begins
                                                           at:
                                               -------------------------
                                                 15.625
                     Event                         kHz
                                                  clock        Time
                                                  pluse   (milliseconds)
                                                (number)
------------------------------------------------------------------------
Preamble......................................         0         0
Processor pause...............................        25         1.600
OCI...........................................        27         1.728
To scan \1\...................................        29         1.856
Pause.........................................  ........         3.406
Midscan point.................................  ........         3.606
FRO scan \1\..................................  ........         3.806
End function (airborne).......................  ........         5.356
End guard time; end function (ground).........  ........         5.600
------------------------------------------------------------------------
\1\ The actual commencement and completion of the TO and FRO scan
  transmissions are dependent upon the amount of proportional guidance
  provided. The time slots provided will accommodate a maximum scan of -
  1.5 degrees to +29.5 degrees. Scan timing shall be compatible with
  accuracy requirements.

The duration of each pulse measured at the half amplitude point shall be at least 100 microseconds, and the rise and fall times shall be less then 10 microseconds. It shall be permissible to sequentially transmit two pulses in each out-of-coverage indication time slot. Where pulse pairs are used, the duration of each pulse shall be at least 50 microseconds, and the rise and fall times shall be less then 10 microseconds. The transmission of out-of-coverage indication pulses radiated from antennas with overlapping coverage patterns shall be separated by at least 10 microseconds.

Note: If desired, two pulses may be sequentially transmitted in each OCI time slot. Where pulse pairs are used, the duration of each pulse must be 45 (5) microseconds and the rise and fall times must be less than 10 microseconds.


 

(D) System test. Time slots are provided in Tables 4a and 4b to allow radiation of TO and FRO test pulses. However, radiation of these pulses is not required since the characteristics of these pulses have not yet been standardized.

(iii) Angle encoding. The encoding must be as follows:

(A) General. Azimuth and elevation angles are encoded by scanning a narrow beam between the limits of the proportional coverage sector first in one direction (the TO scan) and then in the opposite direction (the FRO scan). Angular information must be encoded by the amount of time separation between the beam centers of the TO and FRO scanning beam pulses. The TO and FRO transmissions must be symmetrically disposed about the midscan point listed in Tables 4a, 4b, 5, and 7. The midscan point and the center of the time interval between the TO and FRO scan transmissions must coincide with a tolerance of 10 microseconds. Angular coding must be linear with angle and properly decoded using the formula:

where:

&thetas;=Receiver angle in degrees.

V= Scan velocity in degrees per microsecond.

T0=Time separation in microseconds between TO and FRO beam centers corresponding to zero degrees.

t= Time separation in microseconds between TO and FRO beam centers.
 

The timing requirements are listed in Table 6 and illustrated in Figure 7.

(B) Azimuth angle encoding. Each guidance angle transmitted must consist of a clockwise TO scan followed by a counterclockwise FRO scan as viewed from above the antenna. For approach azimuth functions, increasing angle values must be in the direction of the TO scan; for the back azimuth function, increasing angle values must be in the direction of the FRO scan. The antenna has a narrow beam in the plane of the scan direction and a broad beam in the orthogonal plane which fills the vertical coverage.

(C) Elevation angle encoding. The radiation from elevation equipment must produce a beam which scans from the horizon up to the highest elevation angle and then scans back down to the horizon. The antenna has a narrow beam in the plane of the scan direction and a broad beam in the orthogonal plane which fills the horizontal coverage. Elevation angles are defined from the horizontal plane containing the antenna phase center; positive angles are above the horizontal and zero angle is along the horizontal.

(iv) Clearance guidance. The timing of the clearance pulses must be in accordance with Figure 8. For azimuth elements with proportional coverage of less than 40 degrees (20 degrees for back azimuth), clearance guidance information must be provided by transmitting pulses in a TO and FRO format adjacent to the stop/start times of the scanning beam signal. The fly-right clearance pulses must represent positive angles and the fly-left clearance pulses must represent negative angles. The duration of each clearance pulse must be 50 microseconds with a tolerance of 5 microseconds. The transmitter switching time between the clearance pulses and the scanning beam transmissions must not exceed 10 microseconds. The rise time at the edge of each clearance pulse must be less than 10 microseconds. Within the fly-right clearance guidance section, the fly-right clearance guidance signal shall exceed scanning beam antenna sidelobes and other guidance and OCI signals by at least 5 dB; within the fly-left clearance guidance sector, the fly left clearance guidance signal shall exceed scanning beam antenna sidelobes and all other guidance and OCI signals by at least 5 dB; within the proportional guidance sector, the clearance guidance signals shall be at least 5dB below the proportional guidance signal. Optionally, clearance guidance may be provided by scanning throughout the approach guidance sector. For angles outside the approach azimuth proportional coverage limits as set in Basic Data Word One (Basic Data Word 5 for back azimuth), proper decode and display of clearance guidance must occur to the limits of the guidance region. Where used, clearance pulses shall be transmitted adjacent to the scanning beam signals at the edges of proportional coverage as shown in Figure 8. The proportional coverage boundary shall be established at one beamwidth inside the scan start/stop angles, such that the transition between scanning beam and clearance signals occurs outside the proportional coverage sector. When clearance pulses are provided in conjunction with a narrow beamwidth (e.g., one degree) scanning antenna, the scanning beam antenna shall radiate for 15 microseconds while stationary at the scan start/stop angles.

(3) Data function format. Basic data words provide equipment characteristics and certain siting information. Basic data words must be transmitted from an antenna located at the approach azimuth or back azimuth site which provides coverage throughout the appropriate sector. Data function timing must be in accordance with Table 7a.

                                       Table 6_Angle Scan Timing Constants
----------------------------------------------------------------------------------------------------------------
                                                 Max value                        T[INF]m[/    Pause   T[INF]t[/
                   Function                     of [INF]t[/  T[INF]o[/   V(deg/      INF]      time       INF]
                                                INF](usec)  INF](usec)    usec)     (usec)    (usec)     (usec)
----------------------------------------------------------------------------------------------------------------
Approach azimuth..............................     13,000       6,800       0.02      7,972       600     13,128
High rate approach azimuth....................      9,000       4,800       0.02      5,972       600      9,128
Approach elevation............................      3,500       3,350       0.02      2,518       400        N/A
Back azimuth..................................      9,000       4,800      -0.02      5,972       600      9,128
----------------------------------------------------------------------------------------------------------------
                   Table 7a_Basic Data Function Timing
------------------------------------------------------------------------
                                                 Event time slot begins
                                                         at:\1\
                                               -------------------------
                                                 15.625
                     Event                         kHz
                                                  clock        Time
                                                  pulse   (milliseconds)
                                                (number)
------------------------------------------------------------------------
Preamble......................................         0         0
Data transmission (bits I[INF]13[/INF]-               25         1.600
 I[INF]30[/INF])..............................
Parity transmission (bits I[INF]31[/INF]-             43         2.752
 I[INF]32[/INF])..............................
End function (airborne).......................        45         2.880
End guard time: end function (ground).........  ........         3.100
------------------------------------------------------------------------
\1\ The previous event time slot ends at this time.
            Table 7b_Auxiliary Data Function Timing_(Digital)
------------------------------------------------------------------------
                                                 Event time slot begins
                                                           at:
                                               -------------------------
                                                 15.625
                     Event                         kHz
                                                  clock        Time
                                                  pulse   (milliseconds)
                                                (number)
------------------------------------------------------------------------
Preamble......................................         0         0
Address transmission (bits I[INF]13[/INF]-            25         1.600
 I[INF]20[/INF])..............................
Data transmission: (bits I[INF]21[/INF]-              33         2.112
 I[INF]69[/INF])..............................
Parity transmission (bits I[INF]70[/INF]-             82         5.248
 I[INF]76[/INF])..............................
End function (airborne).......................        89         5.696
End guard time; end function (ground).........  ........         5.900
------------------------------------------------------------------------
         Table 7c_Auxiliary Data Function Timing_(Alphanumeric)
------------------------------------------------------------------------
                                                 Event time slot begins
                                                           at:
                                               -------------------------
                                                 15.615
                     Event                         kHz
                                                  clock        Time
                                                  pulse   (milliseconds)
                                                (number)
------------------------------------------------------------------------
Preamble......................................         0            0
Address transmission (bits I[INF]13[/INF]-            25        1.600
 I[INF]20[/INF])..............................
Data transmission: (bits I[INF]21[/INF]-              33        2.112
 I[INF]76[/INF]...............................
End function (airborne).......................        89        5.696
End guard time; (end function ground).........  ........        5.900
------------------------------------------------------------------------

(i) Preamble. Must be in accordance with requirements of 171.311(i)(1).

(ii) Data transmissions. Basic data must be transmitted using DPSK modulation. The content and repetition rate of each basic data word must be in accordance with Table 8a. For data containing digital information, binary number 1 must represent the lower range limit with increments in binary steps to the upper range limit shown in Table 8a. Data containing digital information shall be transmitted with the least significant bit first.

(j) Basic Data word requirements. Basic Data shall consist of the items specified in Table 8a. Basic Data word contents shall be defined as follows:

(1) Approach azimuth to threshold distance shall represent the minimum distance between the Approach Azimuth antenna phase center and the vertical plane perpendicular to the centerline which contains the landing threshold.

(2) Approach azimuth proportional coverage limit shall represent the limit of the sector in which proportional approach azimuth guidance is transmitted.

(3) Clearance signal type shall represent the type of clearance when used. Pulse clearance is that which is in accordance with 171.311 (i) (2) (iv). Scanning Beam (SB) clearance indicates that the proportional guidance sector is limited by the proportional coverage limits set in basic data.

                        Table 8a_Basic Data Words
------------------------------------------------------------------------
                                             LSB
   Data bit #      Data item definition     value      Data bit value
------------------------------------------------------------------------
                          Basic Data Word No. 1
------------------------------------------------------------------------
1                Preamble................      N/A  1
2                ........................  .......  1
3                ........................  .......  1
4                ........................  .......  0
5                ........................  .......  1
6                ........................  .......  0
7                ........................  .......  1
8                ........................  .......  0
9                ........................  .......  1
10               ........................  .......  0
11               ........................  .......  0
12               ........................  .......  0
13               Approach azimuth to          100m  100m
                  threshold distance (Om-
                  630m).
14               ........................  .......  200m
15               ........................  .......  400m
16               ........................  .......  800m
17               ........................  .......  1600m
18               ........................  .......  3200m
19               Approach azimuth          2  -2
                  proportional coverage
                  limit (negative limit)
                  (0 to -62).
20               ........................  .......  -4
21               ........................  .......  -8
22               ........................  .......  -16
23               ........................  .......  -32
24               Approach azimuth          2  2
                  proportional coverage
                  limit (positive limit)
                  (0 to +62).
25               ........................  .......  4
26               ........................  .......  8
27               ........................  .......  16
28               ........................  .......  32
29               Clearance signal type...      N/A  0=pulse; 1=SB
30               Spare...................  .......  Transmit zero
31               Parity: (13+14+15. .          N/A  N/A
                  .+30 +31=odd).
32               Parity: (14+16+18. .          N/A  N/A
                  .+30 +32=odd).
1  1  1  1  Note 1: Transmit throughout the Approach Azimuth guidance
 sector at intervals of 1.0 seconds or less.
Note 2: The all
 zero state of
 the data field
 represents the
 lower limit of
 the absolute
 value of the
 coded
 parameter
 unless
 otherwise
 noted.
------------------------------------------------------------------------
Basic Data Word
     No. 2
------------------------------------------------------------------------
1                Preamble................      N/A  1
2                ........................  .......  1
3                ........................  .......  1
4                ........................  .......  0
5                ........................  .......  1
6                ........................  .......  0
7                ........................  .......  1
8                ........................  .......  1
9                ........................  .......  1
10               ........................  .......  1
11               ........................  .......  0
12               ........................  .......  0
13               Minimum glide path        0.1  0.1
                  (2.0 to                 6;
                  14.7).
14               ........................  .......  0.2
15               ........................  .......  0.4
16               ........................  .......  0.8
17               ........................  .......  1.6
18               ........................  .......  3.2
19               ........................  .......  6.4
20               Back azimuth status.....  .......  see note 4
21               DME status..............  .......  see note 6
22               ........................  .......  ....................
23               Approach azimuth status.  .......  see note 4
24               Approach azimuth status.  .......  see note 4
25               Spare...................  .......  Transmit zero
26               ......do................  .......   Do.
27               ......do................  .......   Do.
28               ......do................  .......   Do.
29               ......do................  .......   Do.
30               ......do................  .......   Do.
31               Parity: (13+14+15. .          N/A  N/A
                  .+30 +31)=odd).
32               Parity: (14+16+18. .          N/A  N/A
                  .+30 +32=odd).
Note 1: Transmit throughout the Approach Azimuth guidance sector at
 intervals of 0.16 seconds or less.
Note 2: The all
 zero state of
 the data field
 represents the
 lower limit of
 the absolute
 range of the
 coded
 parameter
 unless
 otherwise
 noted.
------------------------------------------------------------------------
Basic Data Word
     No. 3
------------------------------------------------------------------------
1                Preamble................      N/A  1
2                ........................  .......  1
3                ........................  .......  1
4                ........................  .......  0
5                ........................  .......  1
6                ........................  .......  1
7                ........................  .......  0
8                ........................  .......  1
9                ........................  .......  0
10               ........................  .......  0
11               ........................  .......  0
12               ........................  .......  0
13               Approach azimuth          0.5  0.5
                  beamwidth (0.5-         6;
                  4.0) See note 7.
14               ........................  .......  1.0
15               ........................  .......  2.0
16               Approach elevation        0.5  0.5
                  beamwidth (0.5 to       6;
                  2.5) See note 7.
17               ........................  .......  1.0
18               Note: values greater      .......  2.0
                  than 2.5 are
                  invalid.
19               DME distance (Om to         12.5m  12.5m
                  6387.5m.
20               ........................  .......  25.0m
21               ........................  .......  50.0m
22               ........................  .......  100.0m
23               ........................  .......  200.0m
24               ........................  .......  400.0m
25               ........................  .......  800.0m
26               ........................  .......  1600.0m
27               ........................  .......  3200.0m
28               Spare...................  .......  Transmit zero
29               ......do................  .......   Do.
30               ......do................  .......   Do.
31               Parity: (13+14+15. .      .......  ....................
                  .+30 +31=odd).
32               Parity: (14+16+18. .          N/A  N/A
                  .+30 +32=odd).
Note 1: Transmit throughout the Approach Azimuth guidance sector at
 intervals of 1.0 seconds or less.
Note 2: The all
 zero state of
 the data field
 represents the
 lower limit of
 the absolute
 range of the
 coded
 parameter
 unless
 otherwise
 noted.
------------------------------------------------------------------------
Basic Data Word
     No. 4
------------------------------------------------------------------------
1                Preamble................      N/A  1
2                ........................  .......  1
3                ........................  .......  1
4                ........................  .......  0
5                ........................  .......  1
6                ........................  .......  1
7                ........................  .......  0
8                ........................  .......  0
9                ........................  .......  0
10               ........................  .......  1
11               ........................  .......  0
12               ........................  .......  0
13               Approach azimuth          1  1
                  magnetic orientation
                  (0 to 359).
14               ........................  .......  2
15               ........................  .......  4
16               ........................  .......  8
17               ........................  .......  16
18               ........................  .......  32
19               ........................  .......  64
20               ........................  .......  128
21               ........................  .......  256
22               Back azimuth magnetic     1  1
                  orientation (0 to
                  359).
23               ........................  .......  2
24               ........................  .......  4
25               ........................  .......  8
26               ........................  .......  16
27               ........................  .......  32
28               ........................  .......  64
29               ........................  .......  128
30               ........................  .......  256
31               Parity: (13+14+15. .          N/A  N/A
                  .+30 +31=odd).
32               Parity: (14+16+18. .          N/A  N/A
                  .+30 +32=odd).
Note 1: Transmit at intervals of 1.0 second or less throughout the
 Approach Azimuth guidance sector, except when Back Azimuth guidance is
 provided. See Note 8.
Note 2: The all
 zero state of
 the data field
 represents the
 lower limit of
 the absolute
 range of the
 coded
 parameter
 unless
 otherwise
 noted.
------------------------------------------------------------------------
Basic Data Word
     No. 5
------------------------------------------------------------------------
1                Preamble................      N/A  1
2                ........................  .......  1
3                ........................  .......  1
4                ........................  .......  0
5                ........................  .......  1
6                ........................  .......  1
7                ........................  .......  1
8                ........................  .......  0
9                ........................  .......  1
10               ........................  .......  1
11               ........................  .......  0
12               ........................  .......  0
13               Back azimuth              2  -2
                  proportional coverage
                  negative limit (0
                  to -42).
14               ........................  .......  -4
15               ........................  .......  -8
16               ........................  .......  -16
17               ........................  .......  -32
18               Back azimuth              2  2
                  proportional coverage
                  positive limit (0
                  to +42).
19               ........................  .......  4
20               ........................  .......  8
21               ........................  .......  16
22               ........................  .......  32
23               Back azimuth beamwidth    0.5  0.5
                  (0.5 to                 6;
                  4.0) See note 7.
24               ........................  .......  1.0
25               ........................  .......  2.0
26               Back azimuth status.....  .......  See Note 10
27               ......do................  .......   Do.
28               ......do................  .......   Do.
29               ......do................  .......   Do.
30               ......do................  .......   Do.
31               Parity: (13+14+15. .          N/A  N/A
                  .+30 +31=odd).
32               Parity: (14+16+18. .          N/A  N/A
                  .+30 +32=odd).
Note 1: Transmit only when Back Azimuth guidance is provided. See note
 9.
Note 2: The all
 zero state of
 the data filed
 represents the
 lower limit of
 the absolute
 range of the
 coded
 parameter
 unless
 otherwise
 noted.
------------------------------------------------------------------------
Basic Data Word
     No. 6
------------------------------------------------------------------------
1                Preamble................      N/A  1
2                ........................  .......  1
3                ........................  .......  1
4                ........................  .......  0
5                ........................  .......  1
6                ........................  .......  0
7                ........................  .......  0
8                ........................  .......  0
9                ........................  .......  1
10               ........................  .......  1
11               ........................  .......  0
12               ........................  .......  1
(13-             MLS ground equipment      .......  ....................
30)               identification (Note 3).
13               Character 2.............      N/A  B1
14               ........................  .......  B2
15               ........................  .......  B3
16               ........................  .......  B4
17               ........................  .......  B5
18               ........................  .......  B6
19               Character 3.............      N/A  B1
20               ........................  .......  B2
21               ........................  .......  B3
22               ........................  .......  B4
23               ........................  .......  B5
24               ........................  .......  B6
25               Character 4.............      N/A  B1
26               ........................  .......  B2
27               ........................  .......  B3
28               ........................  .......  B4
29               ........................  .......  B5
30               ........................  .......  B6
31               Parity: (13+14+15. .          N/A  N/A
                  .+30 +31=odd).
32               Parity: (14+16+18. .          N/A  N/A
                  .+30 +32=odd).
 Note 1: Transmit at intervals of 1.0 second or less throughout the
  Approach Azimuth guidance sector, except when Back Azimuth guidance is
  provided. See note 8.
 Note 3: Characters are encoded using the International Alphabet Number
  5, (IA-5):
Note 4: Coding for status bit:
0=Function not radiated, or radiated in test mode (not reliable for
  navigation).
1=Function radiated in normal mode (for Back Azimuth, this also
  indicates that a Back Azimuth transmission follows).
Note 5: Date items which are not applicable to a particular ground
  equipment shall be transmitted as all zeros.
Note 6: Coding for status bits:
I[INF]21[/INF]   I[INF]22[/INF].....  ...
0                0..................  DME
                                      tra
                                      nsp
                                      ond
                                       er
                                      ino
                                      per
                                      ati
                                       ve
                                       or
                                      not
                                      ava
                                      ila
                                      ble
                                        .
1                0..................  Onl
                                        y
                                       IA
                                      mod
                                        e
                                       or
                                      DME/
                                        N
                                      ava
                                      ila
                                      ble
                                        .
0                0..................   FA
                                      mod
                                       e,
                                      Sta
                                      nda
                                       rd
                                       1,
                                      ava
                                      ila
                                      ble
                                        .
1                1..................   FA
                                      mod
                                       e,
                                      Sta
                                      nda
                                       rd
                                       2,
                                      ava
                                      ila
                                      ble
                                        .
Note 7: The value coded shall be the actual beamwidth (as defined in
   171.311 (j)(9) rounded to the nearest 0.5 degree.
Note 8: When back Azimuth guidance is provided, Data Words 4 and 6 shall
  be transmitted at intervals of 1.33 seconds or less throughout the
  Approach Azimuth coverage and 4 seconds or less throughout the Back
  Azimuth coverage.
Note 9: When Back Azimuth guidance is provided, Data Word 5 shall be
  transmitted at an interval of 1.33 seconds or less throughout the Back
  Azimuth coverage sector and 4 seconds or less throughout the Approach
  Azimuth coverage sector.
Note 10: Coding for status bit:
0=Function not radiated, or radiated in test mode (not reliable for
  navigation).
1=Function radiated in normal mode.

(4) Minimum glidepath the lowest angle of descent along the zero degree azimuth that is consistent with published approach procedures and obstacle clearance criteria.

(5) Back azimuth status shall represent the operational status of the Back Azimuth equipment.

(6) DME status shall represent the operational status of the DME equipment.

(7) Approach azimuth status shall represent the operational status of the approach azimuth equipment.

(8) Approach elevation status shall represent the operational status of the approach elevation equipment.

(9) Beamwidth the width of the scanning beam main lobe measured at the -3 dB points and defined in angular units on the antenna boresight, in the horizontal plane for the azimuth function and in the vertical plane for the elevation function.

(10) DME distance shall represent the minimum distance between the DME antenna phase center and the vertical plane perpendicular to the runway centerline which contains the MLS datum point.

(11) Approach azimuth magnetic orientation shall represent the angle measured in the horizontal plane clockwise from Magnetic North to the zero-degree angle guidance radial originating from the approach azimuth antenna phase center. The vertex of the measured angle shall be at the approach azimuth antenna phase center.

Note: For example, this data item would be encoded 090 for an approach azimuth antenna serving runway 27 (assuming the magnetic heading is 270 degrees) when sited such that the zero degree radial is parallel to centerline.


 

(12) Back azimuth magnetic orientation shall represent the angle measured in the horizontal plane clockwise from Magnetic North to the zero-degree angle guidance radial originating from the Back Azimuth antenna. The vertex of the measured angle shall be at the Back Azimuth antenna phase center.

Note: For example, this data item would be encoded 270 for a Back Azimuth Antenna serving runway 27 (assuming the magnetic heading is 270 degrees) when sited such that the zero degree radial is parallel to centerline.


 

(13) Back azimuth proportional coverage limit shall represent the limit of the sector in which proportional back azimuth guidance is transmitted.

(14) MLS ground equipment identification shall represent the last three characters of the system identification specified in 171.311(i)(2). The characters shall be encoded in accordance with International Alphabet No. 5 (IA-5) using bits b1 through b6.

Note: Bit b7 of this code may be reconstructed in the airborne receiver by taking the complement of bit b6.


 

(k) Residual radiation. The residual radiation of a transmitter associated with an MLS function during time intervals when it should not be transmitting shall not adversely affect the reception of any other function. The residual radiation of an MLS function at times when another function is radiating shall be at least 70 dB below the level provided when transmitting.

(l) Symmetrical scanning. The TO and FRO scan transmissions shall be symmetrically disposed about the mid-scan point listed in Tables 4a, 4b and 5. The mid-scan point and the center of the time interval between the TO and FRO scan shall coincide with a tolerance of plus or minus 10 microseconds.

(m) Auxiliary data -- (1) Addresses. Three function identification codes are reserved to indicate transmission of Auxiliary Data A, Auxiliary Data B, and Auxiliary Data C. Auxiliary Data A contents are specified below, Auxiliary Data B contents are reserved for future use, and Auxiliary Data C contents are reserved for national use. The address codes of the auxiliary data words shall be as shown in Table 8b.

(2) Organization and timing. The organization and timing of digital auxiliary data must be as specified in Table 7b. Data containing digital information must be transmitted with the least significant bit first. Alphanumeric data characters must be encoded in accordance with the 7-unit code character set as defined by the American National Standard Code for Information Interchange (ASCII). An even parity bit is added to each character. Alphanumeric data must be transmitted in the order in which they are to be read. The serial transmission of a character must be with the lower order bit transmitted first and the parity bit transmitted last. The timing for alphanumeric auxiliary data must be as shown in Table 7c.

(3) Auxiliary Data A content: The data items specified in Table 8c are defined as follows:

(i) Approach azimuth antenna offset shall represent the minimum distance between the Approach Azimuth antenna phase center and the vertical plane containing the runway centerline.

(ii) Approach azimuth to MLS datum point distance shall represent the minimum distance between the Approach Azimuth antenna phase center and the vertical plane perpendicular to the centerline which contains the MLS datum point.

(iii) Approach azimuth alignment with runway centerline shall represent the minimum angle between the approach azimuth antenna zero-degree guidance plane and the runway certerline.

(iv) Approach azimuth antenna coordinate system shall represent the coordinate system (planar or conical) of the angle data transmitted by the approach azimuth antenna.

(v) Approach elevation antenna offset shall represent the minimum distance between the elevation antenna phase center and the vertical plane containing the runway centerline.

(vi) MLS datum point to threshold distance shall represent the distance measured along the runway centerline from the MLS datum point to the runway threshold.

(vii) Approach elevation antenna height shall represent the height of the elevation antenna phase center relative to the height of the MLS datum point.

(viii) DME offset shall represent the minimum distance between the DME antenna phase center and the vertical plane containing the runway centerline.

(ix) DME to MLS datum point distance shall represent the minimum distance between the DME antenna phase center and the vertical plane perpendicular to the centerline which contains the MLS datum point.

(x) Back azimuth antenna offset shall represent the minimum distance between the back azimuth antenna phase center and the vertical plane containing the runway centerline.

(xi) Back azimuth to MLS datum point distance shall represent the minimum distance between the Back Azimuth antenna and the vertical plane perpendicular to the centerline which contains the MLS datum point.

(xii) Back azimuth antenna alignment with runway centerline shall represent the minimum angle between the back azimuth antenna zero-degree guidance plane and the runway centerline.