5.108 The carrier frequency 2 182 kHz is an international distress and calling frequency for radiotelephony. The conditions for the use of the band 2 173.5-2 190.5 kHz are prescribed in Articles 31 and 52. (WRC 07)
5.109 The frequencies 2 187.5 kHz, 4 207.5 kHz, 6 312 kHz, 8 414.5 kHz, 12 577 kHz and 16 804.5 kHz are international distress frequencies for digital selective calling. The conditions for the use of these frequencies are prescribed in Article 31.
5.110 The frequencies 2 174.5 kHz, 4 177.5 kHz, 6 268 kHz, 8 376.5 kHz, 12 520 kHz and 16 695 kHz are international distress frequencies for narrow-band direct-printing telegraphy. The conditions for the use of these frequencies are prescribed in Article 31.
5.111 The carrier frequencies 2 182 kHz, 3 023 kHz, 5 680 kHz, 8 364 kHz and the frequencies 121.5 MHz, 156.525 MHz, 156.8 MHz and 243 MHz may also be used, in accordance with the procedures in force for terrestrial radiocommunication services, for search and rescue operations concerning manned space vehicles. The conditions for the use of the frequencies are prescribed in Article 31.
The same applies to the frequencies 10 003 kHz, 14 993 kHz and 19 993 kHz, but in each of these cases emissions must be confined in a band of ± 3 kHz about the frequency. (WRC 07)
US279 The frequency 2182 kHz may be authorized to fixed stations associated with the maritime mobile service for the sole purpose of transmitting distress calls and distress traffic, and urgency and safety signals and messages.
US340 The band 2-30 MHz is available on a non-interference basis to Federal and non-Federal maritime and aeronautical stations for the purposes of measuring the quality of reception on radio channels. See 47 CFR 87.149 for the list of protected frequencies and bands within this frequency range. Actual communications shall be limited to those frequencies specifically allocated to the maritime mobile and aeronautical mobile services.

Wiki entries

Access Broadband over Power Line (Access BPL)

Current Use 1.705–2.85 MHz Access BPL

According to the FCC's definition, Access BPL is "a carrier current system installed and operated on an electric utility service as an unintentional radiator that sends radio frequency energy on frequencies between 1.705 MHz and 80 MHz over medium voltage lines or over low voltage lines to provide broadband communications and is located on the supply side of the utility service’s points of interconnection with customer premises. Access BPL does not include power line carrier systems as defined in § 15.3(t) or In-House BPL as defined in § 15.3(gg)."

Low voltage lines are defined as lines carrying, for example, 240/120 volts from a distribution transformer to a customer's premises. Medium voltage lines carry between 1,000 and 40,000 volts from a power substation to neighborhoods, and may be overhead or underground.

Access BPL is an unlicensed service operated under Subpart G of Part 15 of the FCC's rules. Radiated emission limits from medium voltage lines in the 1.705-30 MHz range must not exceed the limits in 47 CFR 15.209, and those from 30-80 MHz must not exceed the limits in 15.109(b). Systems that operate on low voltage lines must comply with 15.109(a) limits across the entire 1.705-80 MHz range.

When Access BPL systems must use notch filters to protect licensed services, the notch must be at least 25 dB below applicable Part 15 limits in the 1.705-30 MHz band, and at least 10 dB below the limits in the 30-80 MHz band.

There are 12 sub-bands in which Access BPL systems are not allowed to operate anywhere to protect aeronautical (land) stations and aircraft receivers. Those excluded bands are listed in 15.615(f), and are excluded in the list of Access BPL bands in this entry.

Access BPL systems are not allowed to operate within the sub-band 2173.5-2190.5 kHz within 1 km of coast station facilities listed in 47 CFR 15.615(f)(2)(i), to protect the internationally-recognized standard maritime calling frequency of 2182 kHz.

No Access BPL emissions are allowed in the 73.0-74.6 MHz radio astronomy band on overhead medium voltage lines within 65 km of the Very Large Array radio telescope in New Mexico (34 04 43.5N, 107 37 03.82W), or within 47 km of the VLA on underground power lines or overhead low voltage lines.

Access BPL operators must consult at least 30 days in advance when deploying systems near various FCC field offices, aeronautical and maritime stations, radar systems, radio astronomy stations, and research areas. Details are in 47 CFR 15.615(f)(3).