[Code of Federal Regulations]
[Title 47, Volume 2]
[Revised as of October 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR73.187]
[Page 59-60]
TITLE 47--TELECOMMUNICATION
CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION (CONTINUED)
PART 73_RADIO BROADCAST SERVICES--Table of Contents
Subpart A_AM Broadcast Stations
Sec. 73.187 Limitation on daytime radiation.
(a)(1) Except as otherwise provided in paragraphs (a)(2) and (3) of
this section, no authorization will be granted for a Class B or Class D
station on a frequency specified in Sec. 73.25 if the proposed
operation would radiate during the period of critical hours (the two
hours after local sunrise and the two hours before local sunset) toward
any point on the 0.1 mV/m contour of a co-channel U.S. Class A station,
at or below the pertinent vertical angle determined from Curve 2 of
Figure 6a of Sec. 73.190, values in excess of those obtained as
provided in paragraph (b) of this section.
(2) The limitation set forth in paragraph (a)(1) of this section
shall not apply in the following cases:
(i) Any Class B or Class D operation authorized before November 30,
1959; or
(ii) For Class B and Class D stations authorized before November 30,
1959, subsequent changes of facilities which do not involve a change in
frequency, an increase in radiation toward any point on the 0.1 mV/m
contour of a co-channel U.S. Class A station, or the move of transmitter
site materially closer to the 0.1 mV/m contour of such Class A station.
(3) A Class B or Class D station authorized before November 30,
1959, and subsequently authorized to increase
[[Page 60]]
daytime radiation in any direction toward the 0.1 mV/m contour of a co-
channel U.S. Class A station (without a change in frequency or a move of
transmitter site materially closer to such contour), may not, during the
two hours after local sunrise or the two hours before local sunset,
radiate in such directions a value exceeding the higher of:
(i) The value radiated in such directions with facilities last
authorized before November 30, 1959, or
(ii) The limitation specified in paragraph (a)(1) of this section.
(b) To obtain the maximum permissible radiation for a Class B or
Class D station on a given frequency from 640 through 990 kHz, multiply
the radiation value obtained for the given distance and azimuth from the
500 kHz chart (Figure 9 of Sec. 73.190) by the appropriate
interpolation factor shown in the K500 column of paragraph
(c) of this section; and multiply the radiation value obtained for the
given distance and azimuth from the 1000 kHz chart (Figure 10 of Sec.
73.190) by the appropriate interpolation factor shown in the
K1000 column of paragraph (c) of this section. Add the two
products thus obtained; the result is the maximum radiation value
applicable to the Class B or Class D station in the pertinent
directions. For frequencies from 1010 to 1580 kHz, obtain in a similar
manner the proper radiation values from the 1000 and 1600 kHz charts
(Figures 10 and 11 of Sec. 73.190), multiply each of these values by
the appropriate interpolation factors in the K[min]1000 and
K[min]1600 columns in paragraph (c) of this section, and add
the products.
(c) Interpolation factors. (1) Frequencies below 1000 kHz.
------------------------------------------------------------------------
fkHz K\500\ K\1000\
------------------------------------------------------------------------
640................................................. 0.720 0.280
650................................................. 0.700 0.300
660................................................. 0.680 0.320
670................................................. 0.660 0.340
680................................................. 0.640 0.360
690................................................. 0.620 0.380
700................................................. 0.600 0.400
710................................................. 0.580 0.420
720................................................. 0.560 0.440
730................................................. 0.540 0.460
740................................................. 0.520 0.480
750................................................. 0.500 0.500
760................................................. 0.480 0.520
770................................................. 0.460 0.540
780................................................. 0.440 0.560
800................................................. 0.400 0.600
810................................................. 0.380 0.620
820................................................. 0.360 0.640
830................................................. 0.340 0.660
840................................................. 0.320 0.680
850................................................. 0.300 0.700
860................................................. 0.280 0.720
870................................................. 0.260 0.740
880................................................. 0.240 0.760
890................................................. 0.220 0.780
900................................................. 0.200 0.800
940................................................. 0.120 0.880
990................................................. 0.020 0.980
------------------------------------------------------------------------
(2) Frequencies above 1000 kHz.
------------------------------------------------------------------------
f[min]kHz K[min]\1000\ K[min]\1600\
------------------------------------------------------------------------
1010........................................ 0.983 0.017
1020........................................ 0.967 0.033
1030........................................ 0.950 0.050
1040........................................ 0.933 0.067
1050........................................ 0.917 0.083
1060........................................ 0.900 0.100
1070........................................ 0.883 0.117
1080........................................ 0.867 0.133
1090........................................ 0.850 0.150
1100........................................ 0.833 0.167
1110........................................ 0.817 0.183
1120........................................ 0.800 0.200
1130........................................ 0.783 0.217
1140........................................ 0.767 0.233
1160........................................ 0.733 0.267
1170........................................ 0.717 0.283
1180........................................ 0.700 0.300
1190........................................ 0.683 0.317
1200........................................ 0.667 0.333
1210........................................ 0.650 0.350
1220........................................ 0.633 0.367
1500........................................ 0.167 0.833
1510........................................ 0.150 0.850
1520........................................ 0.133 0.867
1530........................................ 0.117 0.883
1540........................................ 0.100 0.900
1550........................................ 0.083 0.917
1560........................................ 0.067 0.933
1570........................................ 0.050 0.950
1580........................................ 0.033 0.967
------------------------------------------------------------------------
[28 FR 13574, Dec. 14, 1963, as amended at 49 FR 43962, Nov. 1, 1984; 56
FR 64868, Dec. 12, 1991]