136 kHz
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The 136 kHz band is the lowest frequency band in which amateur radio operators are allowed to transmit. It is only available for use in some countries but there is a proposal at the WRC-07 World Radiocommunication Conference to make it a world wide amateur allocation.
The 136 kHz band is in the low frequency (LF) frequency band, just below the longwave broadcasting band. Before its introduction in the UK in 1998, operation on the even lower frequency of 73 kHz had been allowed from 1996 until 2003.
[edit] Technical issues
Such low frequency transmissions require specialist, and therefore usually home made, equipment. In countries where it is allowed, maximum transmission radiated power is usually limited to 1 watt (0 dBW), but even this can be extremely difficult to achieve from practical home made equipment and antennae. Reception also poses problems due to considerable natural and man-made noise and interference (QRN and QRM).
Many users and experimenters have settled on extremely slow, computer-generated and displayed morse code as the most common transmission mode. This mode is known as QRSS, where the doubling of the S emphasises the extreme slowness. The international Q code QRS already stood for slow morse, or "Please send more slowly" in radio jargon.
[edit] Band plan
The 2005 IARU Region 1 Conference defined the band as follows[1]:
- 135.7 - 136.0 kHz
- Station Tests and transatlantic reception window
- 136.0 - 137.4 kHz
- Telegraphy
- 137.4 - 137.6 kHz
- Non-Telegraphy digital modes
- 137.6 - 137.8 kHz
- Very slow telegraphy centred on 137.7 kHz
[edit] United States
There is no 136 kHz amateur allocation in the United States. In 2002, indications from the Federal Communications Commission had been that 136 kHz privileges would be authorized soon. On May 14, 2003, however, the FCC declined to grant these privileges citing concerns over potential interference with power line communications used by electrical utilities to control the power grid.
The FCC added that amateurs wishing to experiment with 136 kHz communications may apply for experimental licenses or operate within existing Part 15 regulations for this part of the electromagnetic spectrum. In the case of Part 15, the field strength measured 300 meters from the antenna may not exceed 2400 microvolts per meter divided by the frequency in kilohertz, or approximately 17 microvolts per meter.
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