Audio Introduction
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The 160 metre amateur radio band, commonly known as Top Band, is one of the oldest and most historically important bands in amateur radio. Operating around 1.8 MHz, just above the medium-wave broadcast band, it has been used by radio amateurs for more than a century. In Britain, it became particularly popular for local contacts, mobile communications, Morse code, and later single-sideband speech.
Unlike the higher-frequency amateur bands, 160 metres has some remarkable characteristics. During daylight it is principally a local communications band, but after dark signals can travel hundreds or even thousands of miles. Although usually included with the HF amateur bands, 160 metres technically falls within the medium-frequency (MF) spectrum, which extends from 300 kHz to 3 MHz.
The history of Top Band
The 160 metre band has its origins in the earliest period of amateur radio. During the 1910s and 1920s, radio amateurs frequently operated on wavelengths around 200 metres and below. These relatively low frequencies were suitable for the valve transmitters and receivers of the period.
At the 1927 International Radiotelegraph Conference in Washington, amateur frequencies between 1.715 and 2 MHz were internationally allocated. As amateurs discovered the advantages of shorter wavelengths, particularly 20 and 40 metres for long-distance communications, the popularity of Top Band declined. However, it remained particularly important in Britain.
Top Band in Britain during the 1950s and 1960s
British radio amateurs made considerable use of 160 metres during the post-war period. It was well suited to relatively short-distance communication between towns and counties, particularly for operators who enjoyed regular conversations rather than chasing distant stations.
Typical equipment included home-built valve transmitters, communications receivers, and later commercial amateur transmitters. Amplitude modulation (AM) was popular, followed by the increasing use of single sideband (SSB). Top Band also became well known for mobile operation, long before the widespread availability of VHF FM repeaters.
Propagation
The behaviour of 160 metres changes dramatically between daylight and darkness.
Daytime operation
Signals normally travel by ground wave over relatively short distances, often tens of miles, although good antennas and favourable ground conditions can extend the range. Ionospheric absorption limits long-distance reception.
Night-time operation
With reduced absorption in the ionosphere’s D region, sky-wave propagation becomes possible. Stations throughout Britain and Europe can be heard, and transatlantic contacts are possible under favourable conditions.
The best conditions often occur during the winter months when nights are longer and atmospheric noise from thunderstorms is generally lower. An especially interesting phenomenon is grey-line propagation, when stations near the sunrise or sunset boundary experience enhanced long-distance signals.
Top band, the greatest band ever! Or, I should say, it was the greatest band ever until a load of cheap switch mode power supplies, phone chargers and other junk entered the country and wiped the band out. But, there is still hope. If you use a separate aerial for receive, such as a loop or active MiniWhip antenna, you might be able to hear stations without the horrendous noise picked up by a conventional wire antenna. An end-fed antenna for top band will work well on transmit and receive, depending on your local noise level.
Aerials for 160 metres:
I use a Kenwood TS-570D for transmitting with an end-fed 100 foot wire. For receiving, I use my Lowe HF-150 with a MiniWhip antenna. I’m about to construct a relay box to mute the HF-150 by shorting the aerial input to the receiver and disconnecting the MiniWhip on transmit. I’ll show details of the relay box once constructed. Another receiver I like using on top band is my trusty old Marconi CR100.
More coming soon...