The International Telecommunication Union's 2007 World Radiocommunication Conference (WRC-07) in Geneva agreed a secondary allocation of 135.7–137.8 kHz to the Amateur Service on Friday 9 November 2007.
In countries where it is allowed, maximum radiated power is usually limited to 1 watt (0 dBW or 30 dBm), but even this can be extremely difficult to achieve from practical equipment and antennas.
[4] On 15 September 2017 the Federal Communications Commission announced[5] that all of the part 97 Amateur Radio Service rules adopted in WRC-12 / FCC 17–33 would now be in effect.
This notification process will ensure that amateur stations seeking to operate in the above noted bands are located beyond a minimum separation distance from PLC transmission lines, which will help ensure the compatibility and coexistence of amateur and PLC operations, and promote shared use of the bands.Previously, in 1998, the FCC rejected an ARRL petition for LF allocations at 135.7–137.8 kHz and 160–190 kHz.
[citation needed] On 19 November 2012, the FCC issued a Notice of Proposed Rulemaking[7] demonstrating intent to authorize the amateur service as a secondary user of the LF band between 135.7–137.8 kHz with a maximum EIRP of 1 watt.
The notice seeks further comment and empirical evidence regarding interference to PLC systems based on data collected by experimental licenses granted in the United States and by other stations around the world.
On 27 April 2015 the Federal Communications Commission announced a preliminary decision to permit amateur operation on a secondary basis from 135.7–137.8 kHz, at a maximum output of 1 watt EIRP.