One of the oldest specializations in amateur radio is called DX-ing. DX is a ham term for distant station. Some hams become involved in amateur radio so that they can contact far-away stations, and they challenge themselves to continue pushing the limits further and further. It is this quest for making contacts in remote areas of the world that often pushes advancements in radio technology. While it is relatively easy to contact people around the globe through the technology of the Internet, making contact over amateur radio requires the right equipment and knowledge of how the sun and seasons affect radio waves. It's a proud accomplishment to log contacts from far away!
There are two ways to DX over ham radio: using shortwave (HF) bands, and using very high frequency (VHF) or ultra high frequency (UHF) bands. The techniques used for each are quite different.
It's important to note that most amateur radio equipment can get involved in DX-ing. While more sophisticated equipment makes it easier, skill and practice can make DX-ing possible on almost any radio and antenna.
The best way to start DX-ing on HF bands is to listen intently. A ham should start listening to near the bottom of the band that the ham's license allows. A ham can stop at each signal and listen to what's happening. Voice accents as well as unusual signal sounds (perhaps hollow sounding) may indicate that the transmission comes from a great distance. That particular signal sound is something that hams get accustomed to hearing as an indicator of a signal traveling great distances. What happens with a shortwave signal as it travels across the globe is that it bounces between the ionosphere and the earth's surface as it travels. Each bounce, or hop, slightly affects the quality of the signal but creates an unmistakable sound. Listening carefully can be the best experience in getting started DX-ing as it helps teach where and when other hams are on these bands and how certain seasons and the sun affect transmission quality.
In general, the "high bands" work well in the daylight, and the "low bands" do better at night. This is because the low bands are absorbed rather than reflected by the ionosphere during the day.
It might be beneficial to have a few extra resources handy for DX-ing. One is a prefix list for call signs. Remember that the prefix of a call sign is unique to a specific country. That can help a ham determine where another ham is located. Another resource is an az-eq map, which is a special flat globe map that puts a ham's location in the center and can help determine how radio waves come from any point on the earth to the ham's antenna.
When DX-ing, most hams keep their messages shorter than they would when speaking to local hams. Additionally, it's good to repeat a call sign several times as both parties need to get each other's call signs correct to confirm contact. Because of the hops of the signal, it's a good idea to speak slowly and crisply, but shouting is of no help. Hams can also send QSL cards to each other after DX contacts as a way to collect proof of places where they've made contact (similar to postcards).
Sometimes, particularly with rare stations, pileups occur, which means that there are a lot of hams trying to make contact with the station at the same time. Usually hams who have noted the station's patterns make the most successful contacts. Some stations also "work split," which means that a station is listening on one frequency and responding on another. The giveaway that a split is occurring is if a ham hears the station but no other hams responding or vice versa.
Hams can win all sorts of awards for successful DX-ing. Some start with making contact with an entity on each continent. Others are making contact with all 50 U.S. states. More challenging awards call for 100 entities, 300 prefixes, and more.
VHF/UHF DX-ing occurs at bands over 30 MHz. What separates these from HF bands is that radio waves do not generally reflect off of the ionosphere, so there is a different way to send and receive signals. Hams may need to have their radios scan the lower end of a band and use a small beam antenna to find success.
Several methods exist for successful DX-ing on VHF/UHF bands. One is using sporadic-E, which involves a lower ionospheric layer. Sometimes, particularly in early summer and winter, the sun lights up the E-layer in a way that makes a highly-ionized region that is excellent for reflecting these bands for a few minutes. Another method uses the aurora to reflect these bands. The aurora has been known to add a distinctive and beautiful sound to the radio transmission. Hams can also use the troposphere, the layer of the atmosphere closest to the earth, to reflect radio waves. This is usually possible only when there are disturbances in the troposphere, such as strong weather fronts. Meteors entering the earth's atmosphere also successfully reflect radio waves. Even though there are thousands of meteors daily, they burn up so quickly that hams can only connect for a few seconds. Finally, some hams actually take their equipment to a higher elevation, called mountaintopping, to try to improve horizon lines to make VHF/UHF DX-ing possible.
Low-power operating, called QRP or flea power in ham radio terms, attracts a significant subset of ham radio operators. Making the intentional choice to use low power and weak radio signals is a challenge that requires great skill. QRP is defined as 5 watts or below of transmitter power for Morse code and up to 10 watts of power for voice transmissions. Some QRP operators try to operate below one watt, called milliwatting.
QRP-ing is usually over HF bands and involves finding a clear frequency and calling CQ, which simply means calling for responses from anyone who may be listening, while the ham's radio is set to QRP levels. Many QRP-ers enjoy building and using their own radio equipment, whether from kits or completely homemade, to try to keep everything as small and light as possible.
As computer technology quickly transforms and develops, new possibilities emerge. In recent history, a fast-growing segment of amateur radio is transmitting digitally, which sends messages via data rather than voice or Morse code. Hams use regular Internet (TCP/IP) protocols for sending data and have also developed their own for ham use. The ionosphere isn't friendly to data flow, so hams have developed protocols that work well by sending data in short bursts.
To use digital ham radio, a ham needs equipment, at least a sound card, to act between the radio and a computer to decode the data. Digital ham radio operates at bands near where Morse code operates, in the upper end of HF bands.
Interestingly enough, one of the earliest digital modes for ham radio came about in the 1930s and is called radioteletype, or RTTY. RTTY uses a 5-bit code called Baudot to send text characters as a series of alternating mark and space patterns on different frequencies. These frequencies operate on normal voice frequencies, so no special transceiver is needed for sending or receiving RTTY. Translating the marks and spaces can be done by a computer with a special sound card or even on antique teleprinters, which some hams still use to this day. Of course, RTTY has its own set of radio clubs, contests, and awards.
AMTOR is a TOR system (teleprinting over radio) and was developed in the 1980s. AMTOR, like RTTY, uses alternating patterns to send text characters. The methods for using AMTOR allow for error correction because sending characters over HF bands with alternating patterns can result in some distortion. (RTTY, on the other hand, does not include error correction.) However, AMTOR is a slow method of transmission because of the error correction features, even though it is a highly reliable technique.
PACTOR is another TOR system that moves faster than AMTOR and is even more reliable. PACTOR is proprietary, however, meaning that a ham that wishes to get involved in PACTOR needs special equipment from the manufacturer.
Packets are yet a different way of sending data over amateur radio. This sends data in a specialized data transfer protocol, complete with error correction, over VHF bands. Data is sent using audio tones, and specialized equipment is used between the radio and a computer. While it is still in use today, packet radio is giving way to WLAN technology on amateur radio bands.
A relatively new way of transmitting data is using PSK31, which was developed by ham Peter Martinex. PSK31 uses a new coding system for text characters, similar to Morse code, but instead of tones going on and off, PSK31 uses one continuous tone, and slight variances in the tone, almost imperceptible to the human ear, signify characters. Because of this continuous tone, receivers can pick up and decode these messages easily, even with noise and other distortions.
WLAN technologies, most often used for wireless computer networks, can also be used by amateur radio operators. High Speed Multimedia Radio (HSMM) is intended to use WLAN technologies to transmit messages over long distances even though computers only use WLAN for short distances.
The first ham satellite, OSCAR-1, was launched in 1961. Additional satellites have been launched by hams all over the world through the years. Some satellites are part of scientific experiments while others are repeaters or digital mailboxes for hams.
Many amateur radio satellites orbit the earth in Low Earth Orbit (LEO) several times a day. Hams can use these satellites in their transmissions using 10-meter, 2-meter, 70-cm, and some microwave bands. Hams send information, called uplink, to the satellite, and the downlink retrieves information from the satellite. To use a satellite, a ham needs to know the location of the satellite using orbital numbers.
One kind of ham radio satellite is the transponder, which takes signals from one band and retransmits them on another band. Repeater satellites perform the same service as their earthly counterparts, simply receiving and repeating signals. Furthermore, digital satellites act as bulletin boards or "store-and-forwarders," which take signals that can be downloaded elsewhere later.
The AMSAT website maintains a list of amateur radio satellites and their modes. To use these satellites, hams need to have satellite tracking software on their computers to find a satellite's orbital numbers. Special radios and omnidirectional antennas are also recommended for optimal performance.
Amateur radio can also be used to send visual images. Similar to fax technology, data can be sent over slow-scan television (SSTV) using converters or a computer. Fast-scan television, or amateur television (ATV), functions more like regular television. Hams can send videos using this technology just as broadcast television would work.
There are many contests for hams to participate in and enjoy. In addition to the thrill of being part of a large gathering of online hams all trying to snatch top honors, it's a great way for hams to push their equipment to the limit to see what it's capable of.
Contests exist for just about any kind of interest and band. Some are very narrow and low-key, and others are large with a short time limit, filling radio waves with lots of frenetic activity. Many contests repeat annually during the same time frame each year. It's simple to find contests using an Internet search or checking out the ARRL website.
Connecting to other hams to solicit contacts is calling CQ. During contests, hams are typically just calling CQs to establish contacts, and this typically takes no more than ten seconds. Hams simply need to exchange call signs and locations. Each contact is then valid for QSO points, which are assigned based on contest rules.
Many hams will scan frequencies listening for other hams who are calling CQ. These hams then respond to the caller, and then wait to be acknowledged so that they can exchange information. Other hams find a good frequency and call CQ, waiting for other hams to respond to the call.
Following a contest, hams complete the appropriate logs with the information requested by contest officials and send their logs in electronically, by mail, or by disk to meet a deadline. Contest officials tally results and cross-check log entries and then publish the winners.
Most ham radio awards differ from contests in that they are ongoing without time limits, or their limits are quite extended. Awards can be similar to the DX-ing types, where a certain number of contacts from various areas are sought. Some are for specific areas only, and others are more for making contact with a particular occasion.