Just above the mediumwave broadcast band, 160 meters is the lowest radio frequency band allocation available to amateur radio operators in most countries. Seasoned operators often refer to 160 meters as the Top Band. It is also sometimes referred to as the "Gentleman's Band" in contrast to the often-freewheeling 80 and 20 meter band activity.
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The 160 meter band is the oldest amateur band and was the staple of reliable communication in the earliest days of amateur radio, when almost all communications were over relatively short distances. The band was allocated on a worldwide basis by the International Radiotelegraph Conference in Washington, D.C., on October 4, 1927. The allocation was 1715–2000 kHz. The 1947 International Radio Conference of Atlantic City reduced the allocation to 1800-2000 kc under the provision that amateurs must not interfere with Loran operation.
As the high frequency bands were developed in mid 1920s — along with their smaller, more convenient antennas — 160 meters fell in to a period of relative nonuse. Although there has always been activity on the band, fewer and fewer hams are willing to put up the antennas necessary to take advantage of the band's unique properties. For most amateurs, the HF bands are much easier to use and HF antennas need a lot less real estate.
After World War II, the 160 meter band was apparently not coming back. A large part of the U.S. 160 meter band was allocated on a primary basis to the LORAN radio-navigation system that began operating in and around the 160 meter band in 1942. Amateurs were relegated to secondary, non-interfering status, with severe regional power limitations and restricted day/night operations on just a few narrow segments of the band.
Many older hams recall, with no great fondness, the ear-shattering buzz-saw racket of high power LORAN stations that began in 1942 until LORAN-A was phased out in North America on December 31, 1980 and most of the world by 1985. LORAN-A was still operating in China and Japan in 1995.
Great ingenuity was used to eliminate the pulse noise of the powerful LORAN-A transmitters through such famous circuitry as the "Select-O-Ject" of the late 1950s. The technology was adapted to modern noise blanking circuits used in current amateur receivers and transceivers.
Despite many obstacles and threats from commercial and military spectrum users, the efforts of a small number of determined 160 meter operators enabled the band to survive. The band experienced a rebirth with the demise of LORAN-A in the United States in December, 1980 and the removal of power restrictions below 1900 kHz soon thereafter. Power restrictions above 1900 kHz were removed in March 1984. 160 meters was then no longer regarded as the "orphan" band as it had been for more than half a century.
Effective 160 meter operation can be particularly challenging, as full sized antennas (on the order of a quarter-wavelength or more), are difficult to erect for many amateurs with limited space. Nevertheless, many radio amateurs successfully communicate over very long distances with relatively small antennas. 160 meters is populated by many highly dedicated experimenters, as it is a proving ground for ingenuity in antenna design and operating technique.
Much about ionospheric and propagation on 160 meters is still not completely understood. Phenomena such as "chordal hop" propagation are frequently observed, as well as other unexplained long-distance propagation mechanisms. Inexplicable radio blackouts — sometimes encountered on the AM broadcast band — also occur on 160 meters. Many of these phenomena have been investigated in the scientific community, while 160 meter operators continue to be in a unique position to further investigate such fascinating mysteries. The original "magic of radio" is very much alive and well on 160 meters.
The International Telecommunications Union allocated the frequencies from 1810 - 2000 KHz to amateur radio operations in ITU Region 1 (Europe, Greenland, Africa, the Middle East west of the Persian Gulf and including Iraq, the former Soviet Union and Mongolia) and 1800 - 2000 kHz in the rest of the world.
| Range | Band | ITU Region 1 | ITU Region 2 | ITU Region 3 |
|---|---|---|---|---|
| LF | 2200 m | 135.7 kHz - 137.8 kHz | ||
| MF | 160 m | 1.810 MHz - 1.850 MHz | 1.800 MHz - 2.000 MHz | 1.800 MHz - 2.000 MHz |
| HF | 80 / 75 m | 3.500 MHz - 3.800 MHz | 3.500 MHz - 4.000 MHz | 3.500 MHz - 3.900 MHz |
| 60 m1 | 5.250 MHz - 5.450 MHz | |||
| 40 m | 7.000 MHz - 7.200 MHz | 7.000 MHz - 7.300 MHz | 7.000 MHz - 7.200 MHz | |
| 30 m2 | 10.100 MHz - 10.150 MHz | |||
| 20 m | 14.000 MHz - 14.350 MHz | |||
| 17 m2 | 18.068 MHz - 18.168 MHz | |||
| 15 m | 21.000 MHz - 21.450 MHz | |||
| 12 m2 | 24.890 MHz - 24.990 MHz | |||
| 10 m | 28.000 MHz - 29.700 MHz | |||
| VHF | 6 m | 50.000 MHz - 52.000 MHz1 | 50.000 MHz - 54.000 MHz | 50.000 MHz - 54.000 MHz |
| 4 m1 | 70.000 MHz - 70.500 MHz | |||
| 2 m | 144.000 MHz - 146.000 MHz | 144.000 MHz - 148.000 MHz | 144.000 MHz - 148.000 MHz | |
| 1.25 m | 220.000 MHz - 225.000 MHz | |||
| UHF | 70 cm | 430.000 MHz - 440.000 MHz | 420.000 MHz - 450.000 MHz3 | 420.000 MHz - 450.000 MHz3 |
| 33 cm | 902.000 MHz - 928.000 MHz | |||
| 23 cm | 1.240 GHz - 1.300 GHz | |||
| 13 cm | 2.300 GHz - 2.450 GHz | |||
| SHF | 9 cm | 3.400 GHz - 3.475 GHz3 | 3.300 GHz - 3.500 GHz | 3.300 GHz - 3.500 GHz |
| 5 cm | 5.650 GHz - 5.850 GHz | 5.650 GHz - 5.925 GHz | 5.650 GHz - 5.850 GHz | |
| 3 cm | 10.000 GHz - 10.500 GHz | |||
| 1.2 cm | 24.000 GHz - 24.250 GHz | |||
| EHF | 6 mm | 47.000 GHz - 47.200 GHz | ||
| 4 mm3 | 75.500 GHz1 - 81.500 GHz | 76.000 GHz - 81.500 GHz | 76.000 GHz - 81.500 GHz | |
| 2.5 mm | 122.250 GHz - 123.000 GHz | |||
| 2 mm | 134.000 GHz - 141.000 GHz | |||
| 1 mm | 241.000 GHz - 250.000 GHz | |||
| THF | Sub-mm | Some administrations have authorized spectrum for amateur use in this region. | ||
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1 This is not mentioned in the ITU's Table of Frequency Allocations, but it is a de facto international amateur radio allocation. |
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| See also: Radio spectrum · Electromagnetic spectrum | ||||