74.706—Digital TV (DTV) station protection.
(a)
For purposes of this section, the DTV station protected service area is the geographic-area in which the field strength of the station's signal exceeds the noise-limited service levels specified in § 73.622(e) of this chapter. The extremity of this area (noise-limited perimeter) is calculated from the authorized maximum radiated power (without depression angle correction), the horizontal radiation pattern, and height above average terrain in the pertinent direction, using the signal propagation method specified in § 73.625(b) of this chapter.
(b)
(1)
An application to construct a new low power TV or TV translator station or change the facilities of an existing station will not be accepted if it specifies a site which is located within the noise-limited service perimeter of a co-channel DTV station.
(2)
Due to the frequency spacing which exists between TV channels 4 and 5, between Channels 6 and 7, and between Channels 13 and 14, adjacent channel protection standards shall not be applicable to these pairs of channels.
(c)
The low power TV, TV translator or TV booster station field strength is calculated from the proposed effective radiated power (ERP) and the antenna height above average terrain (HAAT) in pertinent directions.
(1)
For co-channel protection, the field strength is calculated using Figure 9a, 10a, or 10c of § 73.699 (F(50,10) charts) of part 73 of this chapter.
(2)
For adjacent channel protection, the field strength is calculated using Figure 9, 10, or 10b of § 73.699 (F(50,50) charts) of part 73 of this chapter.
(d)
A low power TV, TV translator or TV booster station application will not be accepted if the ratio in dB of its field strength to that of the DTV station (L/D ratio) fails to meet the following:
(1)
−2 dB or less for co-channel operations. This maximum L/D ratio for co-channel interference to DTV service is only valid at locations where the signal-to-noise (S/N) ratio is 25 dB or greater. At the edge of the noise-limited service area, where the S/N ratio is 16 dB, the maximum L/D ratio for co-channel interference from analog low power TV, TV translator or TV booster service into DTV service is −21 dB. At locations where the S/N ratio is greater than 16 dB but less than 25 dB, the maximum L/D field strength ratios are found from the following Table (for values between measured values, linear interpolation can be used):
| Signal-to-noise ratio(dB) | DTV-to-low power ratio (dB) |
|---|---|
| 16.00 | 21.00 |
| 16.35 | 19.94 |
| 17.35 | 17.69 |
| 18.35 | 16.44 |
| 19.35 | 7.19 |
| 20.35 | 4.69 |
| 21.35 | 3.69 |
| 22.35 | 2.94 |
| 23.35 | 2.44 |
| 25.00 | 2.00 |
(i)
The DTV noise-limited perimeter if a low power TV, TV translator or TV booster station is located outside that perimeter.
(ii)
At all points within the DTV noise-limited area if a low power TV or TV translator is located within the DTV noise-limited perimeter, as demonstrated by the applicant.
[62 FR 26721, May 14, 1997, as amended at 63 FR 13563, Mar. 20, 1998; 64 FR 4327, Jan. 28, 1999]