Section 73.509 - Prohibited overlap(a) An application for a new or modified NCE-FM station other than a Class D (secondary) station will not be accepted if the proposed operation would involve overlap of signal strength contours with any other station licensed by the Commission and operating in the reserved band (Channels 200-220, inclusive) as set forth in Table 1 to this paragraph (a): Table 1 to Paragraph (a)
| Frequency separation | Contour of proposed station | Contour of other station |
| Co-channel | 0.1mV/m (40 dBu)
1 mV/m (60 dBu) | 1 mV/m (60 dBu)
0.1 mV/m (40 dBu) |
| 200 kHz | 0.5 mV/m (54 dBu)
1 mV/m (60 dBu)1 | 1 mV/m (60 dBu)
0.5 mV/m (54 dBu) |
| 400 kHz/600 kHz | 100 mV/m (100 dBu)
1 mV/m (60 dBu) | 1 mV/m (60 dBu)
100 mV/m (100 dBu) |
(b) An application by a Class D (secondary) station, other than an application to change class, will not be accepted if the proposed operation would involve overlap of signal strength contours with any other station as set forth in Table 2 to this paragraph (b): Table 2 to Paragraph (b)
| Frequency separation | Contour of
proposed station | Contour of
any other station |
| Co-channel | 0.1 mV/m (40 dBu) | 1 mV/m (60 dBu) |
| 200 kHz | 0.5 mV/m (54 dBu) | 1 mV/m (60 dBu) |
| 400/600 kHz | 100 mV/m (100 dBu) | 1 mV/m (60 dBu) |
(c) The following standards must be used to compute the distances to the pertinent contours: (1) The distance of the 60 dBu (1 mV/m) contours are to be computed using Figure 1 of § 73.333 [F(50,50) curves] of this part.(2) The distance to the other contours are to be computed using Figure 1a of § 73.333 [F(50,10) curves]. In the event that the distance to the contour is below 16 kilometers (approximately 10 miles), and therefore not covered by Figure 1a, curves in Figure 1 must be used.(3) The effective radiated power (ERP) that is the maximum ERP for any elevation plane on any bearing will be used.(d) An application for a change (other than a change in channel) in the facilities of a NCE-FM broadcast station will be accepted even though overlap of signal strength contours, as specified in paragraphs (a) and (b) of this section, would occur with another station in an area where such overlap does not already exists, if: (1) The total area of overlap with that station would not be increased;(2) The area of overlap with any other station would not increase;(3) The area of overlap does not move significantly closer to the station receiving the overlap; and,(4) No area of overlap would be created with any station with which the overlap does not now exist.(e) The provisions of this section concerning prohibited overlap will not apply where the area of such overlap lies entirely over water.50 FR 27962, July 9, 1985, as amended at 52 FR 43765, Nov. 16, 1987; 65 FR 79778 , Dec. 20, 2000; 87 FR 15343 , Mar. 18, 2022