of the United States and Canada. During spring and summer (year-round in the tropics), lightning from distant storms creates significantly higher background noise levels, often becoming an insurmountable obstacle to maintaining normal communications. Nearby convective weather activity during the summer months can make the band completely unusable, even for local communications. In the winter months during the peak years of the sunspot cycle, auroral effects can also render the band useless for hours at a time. Frequency allocation The International Telecommunication Union allocated the whole 500 kHz from 3.5 to 4 MHz to amateurs in the Americas, and 3.5 to 3.8 or 3.9 MHz to amateurs in other parts of the world. However, amateurs outside the Americas must share this useful piece of spectrum with other users, usually on a joint primary basis. As a result, authorities in the affected parts of the world restrict amateur allocations between 3.7 MHz and the top of the band. Some allocations are as follows (in MHz): Argentina 3.500–3.750, 3.790–3.800 Australia 3.500–3.700, 3.776–3.800 (Latter is a DX window for advanced licensees only) Canada 3.500–4.000 Europe 3.500–3.800 India 3.500–3.700, 3.890–3.900 Korea 3.500–3.550, 3.790–3.800, (Digital: 3.520 ~ 3.525 MHz) Japan 3.500–3.575, 3.599–3.612, 3.680–3.687, 3.702–3.716, 3.745–3.770, 3.791–3.805, New Zealand 3.500–3.900 Russia 3.500–3.800 United States 3.500–4.000 Lower band edge The lower edge of 80 meters is predominated by CW emissions, with the lower 10 kHz (3.5–3.51 MHz) primarily used for long-distance communications. It is common for illegal marine operations, generally using USB voice, to occupy frequencies on the low end of 80 meters. Most operations of this type are from fishing vessels. Most come from SE Asia and South American ports, although some illegal use occurs with vessels from USA and Canadian ports. Upper band edge For Canadian and U.S. Amateurs with perfect transmitters, the highest usable frequency in the 80 m band for lower side band phone is 3.999 MHz. Depending on quality and condition of radio, audio characteristics, and proper adjustments the bulk of emissions on lower sideband will typically occupy 3.9970–3.9997 MHz. All SSB transceivers have third- and fifth-order products of significant level, typically only 30–35 dB below PEP for third order intermodulation. This means any operation above 3.998 MHz LSB comes with some risk of illegal emissions, even with good equipment. It is a common misconception that using this carrier frequency is not legal as emissions extend beyond the 4 MHz band edge. High