Broadcast & Shortwave
Broadcast & Shortwave
Contents
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B'cast/Shortwave
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Scanning
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Outback/Marine
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CB
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Amateur
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Projects
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Shortwave Listening
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Shortwave listening is a popular activity whose participants specialise in receiving
radio signals from around the world. Signals may include international broadcasters (eg BBC, Voice of America, Radio Japan, Radio Australia), maritime and aircraft communications, pirate broadcasters, military operations and amateur and CB radio activity. Unlike the normal medium wave (AM) or VHF (FM) signals from local radio stations, shortwave signals can travel worldwide. However to hear them, a special receiver, capable of tuning frequencies between 2 and 30 MHz is required. Details of suitable equipment are provided later.
What can be heard on shortwave?The following are a few of the uses for shortwave (or HF) radio. International broadcast stations The shortwave bands are filled with broadcast stations different from those transmitting on the AM and FM bands. Most countries have an international broadcasting service. Religious groups and private organisations also operate shortwave stations. There are many reasons for people listening to shortwave. People may wish to hear news from different points of view, gain greater international understanding or hear transmissions in a particular language. Listening can also be an exciting challenge, especially if tuning into low-powered or infrequent transmissions, such as occur from clandestine, pirate and military stations. Also the programs of shortwave broadcasters can make a pleasant change for those bored with offerings from the local stations. Amateur and CB radio Amateur radio is a non-commercial activity for people interested in radio technology and communication. Communication is worldwide via voice, morse, image and data modes. More information on amateur radio appears on the amateur radio page. CB radio is ideal for the individual wanting low-cost local communication. Details of CB activity and frequencies appear on the CB page. Marine and outback communication HF marine communications include low-power 27 MHz (for the inshore recreational user) and high-power HF for ocean-going vessels. The latter mostly uses frequencies between 2 and 16 MHz and can be heard thousands of kilometres away. HF marine listening is particularly interesting during events such as the Sydney-Hobart Yacht Race, during which frequencies can be very active. Outback communications includes School of the Air, the Royal Flying Doctor Service, and the Australian National 4WD Radio Network. RFDS frequencies are within the 'Fixed and mobile' allocations on the frequency list below. Further details appear on the Outback/Marine communications page.
Military and 'Utility' stations Utility stations can include two-way communication, 'numbers stations', beacons and more. Reception can be hard as signals are often weak and do not come on at known times (unlike broadcasters). A regular column dealing with this aspect of listening appears in Radio & Communications.
HF FrequenciesThe following is a (very incomplete) list of HF frequency allocations in Australia.
1.8 – 1.875 MHz 160 metre amateur
2.182 MHz Marine distress
2.0 – 2.4 MHz Fixed and mobile
2.3 – 2.5 MHz 120 metre broadcast
2.500 MHz WWV/WWVH time signals
2.628 MHz AXM Weatherfax
3.2 - 3.5 MHz 90 metre broadcast
3.5 – 3.8 MHz 80 metre amateur
3.8 - 4.0 MHz 75 metre broadcast
4.0 – 4.1 MHz Fixed and mobile
4.8 – 5.1 MHz 60 metre broadcast
5.000 MHz WWV/WWVH time signals
5.1 – 5.7 MHz Fixed and mobile
5.100 MHz AXM Weatherfax
5.410 MHz Alice Springs RFDS
5.455 MHz Australian National 4WD Network
5.7 – 6.2 MHz 49 metre broadcast
6.8 – 7.0 MHz Fixed and Mobile
7.0 – 7.3 MHz 40 metre amateur
7.1 – 7.5 MHz 41 metre broadcast
7.535 MHz AXI Weatherfax
9.4 – 9.9 MHz 31 metre broadcast
10.000 MHz WWV/WWVH time signals
10.1 – 10.15 MHz 30 metre amateur
11.030 MHz AXM Weatherfax
11.6 – 12 MHz 25 metre broadcast
13.6 – 13.9 MHz 21 metre broadcast
13.920 MHz AXM Weatherfax
14.0 – 14.35 MHz 20 metre amateur
15.000 MHz WWV/WWVH time signals
15.1 – 15.5 MHz 19 metre broadcast
15.615 MHz AXI Weatherfax
17.6 – 17.9 MHz 16 metre broadcast
18.068–18.168MHz 17 metre amateur
20.000 MHz WWV/WWVH time signals
20.469 MHz AXM Weatherfax
21.0 – 21.45 MHz 15 metre amateur
21.45 – 21.8 MHz 13 metre broadcast
24.89 – 24.99 MHz 12 metre amateur
25.6 – 26.1 MHz 11 metre broadcast
26.965-27.405MHz 27 MHz CB
27.62 – 27.98 MHz 27 MHz marine
27.880 MHz Marine distress
28.0 – 29.7 MHz 10 metre amateur
EquipmentShortwave receivers vary in price from less than $100 to $1000 or more. The cheaper sets are only suitable for receiving shortwave broadcasts. This is because they may miss non-broadcast frequencies and do not have a beat-frequency oscillator (BFO) that is required for single sideband, morse and data communication. Cheaper receivers also often have poor frequency stability, dial resolution and can be hard to tune. The main things to look for in a budget receiver are frequency coverage (at least 6-18 MHz desirable), number of bands (one or two make tuning difficult), availability of bandspread (the cheaper receivers achieve this by having seven or eight bands covering just the broadcast frequencies) sensitivity and audio quality. Sets with digital tuning do not drift in frequency, have easier tuning and include 'memories' for storing often used frequencies. To receive other than shortwave broadcasters a better receiver is needed. This can either be one of the better portables or (preferably) a tabletop communications receiver. All of these receivers have a tuning knob, receive SSB and cover the entire HF spectrum. When selecting a receiver for this purpose, choose one with a rotary tuning knob (not up/down switches) and one where the set does not go silent while you are adjusting the tuning. The cheapest portables are available from two dollar shops and have either analogue or (increasingly) digital readouts. They are really only suitable for broadcast listening as do not receive SSB. In the middle of the range are portable sets made by companies such as Sangean, Sony and Grundig. These have superior frequency stability and may recieve SSB transmissions. At the top of the range are the communications receivers, from manufacturers such as Yaesu and Icom. These sets provide continuous HF coverage, good quality AM and SSB reception and are used by more serious listeners. They are stocked by the specialist amateur radio shops. Alternatively, a strong second-hand market exists, with sets often coming up for sale at hamfests and online. AntennasThe telescopic whip antennas on the more sensitive portable receivers will receive a range of broadcast signals, but most receiver will benefit from adding an outside wire antenna. If reception of a single frequency is desired, an antenna called a half-wave dipole fed with coaxial cable will work well. Multiband reception is possible on a simple wire antenna brought straight to the receiver via an antenna tuning unit. In its simplest form, such an antenna can be a length of wire approximately 10-30 metres long mounted as high as possible. Shortwave antenna kits with wire, insulators and rope are available from major electronic retailers. Trees, fences, chimneys and TV antenna masts are all good mounting points for a shortwave antenna. Keep wire antennas clear of power lines to reduce interference and safety risks. Constructional information on simple antennas and tuning units appear on Peter Parker's Projects Page.
PropagationShortwave signals bounce off the ionosphere one or more times between the transmitter site and your receiver. The ability of the ionosphere to reflect radio signals depends on sunspot activity and the time of day. Generally frequencies between 2 and 12 MHz provide best results at night. In contrast, frequencies between 12 and 30 MHz provide daytime long distance reception. In Australia, the shortwave bands are most active in the early morning and around sunset. At these times strong signals may be heard across both of the above frequency ranges. The worst time for shortwave reception is around noon, when signals are usually quite weak. Higher frequencies are generally better than lower frequencies for long-distance communications, but tend to be less reliable, owing to the influence of the 11-year sunspot cycle. Frequencies between 2 and 4 MHz are best for distances up to about 1000 kilometres at night, while 4 to 6 MHz supports communication up to about 3000 kilometres. Frequencies above 6 MHz are good for intercontinental communication. The main exceptions to this are shortwave broadcast stations, which use more power and better antennas than most amateur, fixed and mobile stations. Compared to reception of the local AM and FM stations, which can be heard on the same frequency 24 hours a day, shortwave reception is more hit and miss. The stations you'll be able to hear vary with the time of day, depending on signal propagation, frequency used, transmitting schedules, interference and other factors. Thus you cannot expect quite the same sound quality on shortwave as obtainable from the local AM and FM stations and may need to change frequency as propagation conditions change during the day. Also, not all countries have a shortwave broadcasting service, so if your interested in broadcasts from a specific country or language, it would be well to establish that such transmissions exist and the times and frequencies used are suitable for reception in Australia before lashing out on an expensive receiver. Operating a shortwave receiverA shortwave receiver has a few more controls than a standard AM/FM radio. As with scanners, learn the basics of being able to enter a frequency, tune across a band and set the receiver's mode (if adjustable). Connect an antenna and try tuning some of the above frequency allocations for activity.
Long-distance broadcast listeningBroadcast listeners concentrate their listening on the AM and FM radio bands. Others are also interested in long-distance TV reception. Though AM and FM broadcasters aim for a local audience, extended range propagation and/or special antennas can allow long-distance reception. More serious listeners go on expeditions in an effort to report reception of normally rare or weak stations. The following are some frequency allocations used in Australia: AM broadcast 531 kHz … 1602 kHz in 9 kHz steps
AM narrowcast 1611, 1620, 1629, 1638 up to 1701 kHz approx
FM narrowcast 87.5 – 87.9 MHz approx
FM broadcast 88.1 … 107.7 MHz in 200 kHz steps
Apart from a few modern receivers designed specifically for quality AM reception, older transistor radios often perform better than newer models for long-distance AM reception. However performance of all receivers can be improved by constructing a directional loop antenna. One is described on Peter Parker's Projects Page.
Those interested in long-distance FM can improve reception by building or buying a directional beam antenna. This should be connected to the receiver's antenna terminals. Because FM transmissions take place in the VHF band, a hilltop location will bring in the distant signals, with the main challenge in densely populated areas being able to separate two stations on the one frequency.
Low frequency listeningLower in frequency than the AM broadcast band is the low frequency (or long wave) band. The main use for this part of the spectrum in Australia is aircraft navigation beacons (NDBs), which transmit in the 200 – 480 kHz range. These beacons transmit their callsign (which is a two or three letter abbreviation of their location) in slow morse code, with a few transmitting voice weather information in AM. Hundreds of beacons are active; during a recent evening listening test in suburban Melbourne, some eighty were heard, some as far away as Kalgoorlie and Mt Isa, with just a small ferrite rod loopstick as an antenna. A list of beacons appears on VK2ZTO's website (link below). In New Zealand and PNG, amateur radio operators have access to some frequencies below 200 kHz. Though Australian amateurs do not yet have an allocation, a small number of 'scientific licences' have been issued to Australian experimenters. The most regular transmissions come from AX2TAR in Tasmania, but I have yet to hear them here in Melbourne.
Listening LinksAustralian Broadcasting Authority's list of Australian radio and TV broadcasting stations Australian Communications Authority online RF database Electronic DX Press shortwave newsletter
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