160 metres, often known as Top Band, is technically a Medium Frequency (MF) band, the only one licensed to amateurs. It is slightly higher in frequency than the AM broadcast band (540 kHz - 1600 kHz), and behaves similarly. 160 meters is in many countries the lowest-frequency band on which amateurs are licensed to operate.
As one wavelength is one tenth of a mile, antennas tend to be large and require a large amount of land space, leaving fewer stations able to efficiently transmit on this band compared to the more popular HF frequencies. This smaller number of users has resulted in 160 metres being given the nickname of the "gentleman's band".
Radio communication on 160 metres is prone to extreme D-layer absorption during the day. This typically limits communication to 75 miles. At night, however, the D-layer weakens and contacts can be mode over thousands of kilometres. Like the HF bands, 160 metres usually supports such long-distance communication through refraction of signals via the F2 layer.
Natural noise levels (QRN) are high on this band and signals are more vulnerable to impulse noise at low frequencies, rendering operation somewhat more difficult than on higher-frequency bands. The band had also long been subject to interference from marine navigation systems such as LORAN, although the replacement of these systems by GPS has largely eliminated this issue.
Access : Advanced licencees only
1.800 - 1.810MHz Digital modes
1.810 - 1.840MHz CW only
1.840 - 1.875MHz SSB/AM
|HF and MF||160 metres * 80 metres* 60 metres * 40 metres * 30 metres * 20 metres * 17 metres * 15 metres * 12 metres * 10 metres|
|VHF||6 metres * 4 metres * 2 metres * 1.25 metres|
|UHF||70 centimetres * 33 centimetres * 23 centimetres * 13 centimetres|
|Microwave||9 centimetres * 6 centimetres * 3 centimetres * 1.25 centimetres * Bands above 24GHz|
|See also||US bandplan|