Ham Radio Activities
Although a ham radio does broadcast in all directions, hams generally do not use their radios in a broadcast kind of way as a disk jockey would at a radio station. In normal AM or FM radio, one disk jockey transmits and thousands of people listen. Hams, on the other hand, conduct two-way conversations, often with another ham or with a group of hams in an informal roundtable. The roundtable of hams may be in the same town, county, state, country or continent or may consist of a mix of countries, depending on the frequency and the time of the day. Hams also participate in networks, often called nets, at predetermined times and frequencies to exchange third-party messages. In the case of disasters, hams exchange health and welfare information with other hams. Some hams use radioteletype, (RTTY) with computer screens replacing the noisy teletype machines of the past.
Computer-assisted radioteletype
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Many hams get their start on VHF FM, using battery-operated hand-held transceivers set to transmit on one frequency and receive on another frequency. They use FM repeaters, set up and supported by local radio clubs. These repeaters borrow antenna space from TV-station-tower owners on top of mountains and high buildings to receive and re-broadcast signals to extend the range.
When deadly floods struck central and southern Texas in mid-October 1998, amateur radio operators from four states volunteered their time. Susan Manor, NF0T, is shown helping with communications at the New Braunfels Red Cross office.
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The FM repeater receives one signal at a time and simultaneously rebroadcasts it on another frequency using many more watts of power than available from a small hand-held radio. This extends the range of the hand-held radio from a few miles to tens or hundreds of miles! The whole country has these repeaters! (Listen to one with a radio scanner to learn a lot about ham radio.) When a ham is traveling, he or she can find a repeater to use (great for tips on local restaurants), and carry on a nice, static-free, FM-radio-quality conversation via a radio that fits in the shirt pocket or purse. Linked repeaters allow fun wireless communications across an entire state with a hand-held radio.
Repeaters use common transmit and receive frequency pairs. The frequency pairs in use are informally assigned by groups of hams so that any frequency pair in use is far enough from another repeater so as not to cause unwanted interference.
Amateur radio satellites are a cutting-edge use of technology in amateur radio. Radio amateurs use their hand-held radios to communicate through an amateur radio satellite when the satellite is overhead. A current British satellite has a receiver (uplink) at 145.975 MHz and simultaneously rebroadcasts (downlink) at 435.070 MHz for one station at a time, as a repeater.
Natural disasters like hurricanes or tornadoes disrupt normal telephone and cell phone systems. Ham radio operators pitch in to help with emergency communications, and you will often hear about them on news reports.
On Space Shuttle missions, each member of the crew usually has an amateur radio operator's license. During breaks, astronauts hold their 1- to 5-watt VHF FM hand-held radios up to the shuttle window and chat with other hams for a few minutes, often at schools while the shuttle is in an orbit overhead! VHF transmissions have a limit to line-of-sight communications and normally do not travel over the horizon, so a conversation is limited to the time when the shuttle is overhead. The space station MIR used 145.985 MHz for similar conversations. Future ham radio efforts in space will focus on the use of amateur radio within the International Space Station (ARISS) project.
Ham Radio Equipment
A typical ham radio is a transmitter and a receiver, usually purchased as one unit, called a transceiver. Newer transceiver models often have semi-complicated controls and menu systems that may take some reading of the manual. You may be able to find an older transceiver with controls that are easier to use as a beginner, having the usual analog controls.
Vintage tube-type short-wave receiver
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Hand-held transceivers have their own antennas. Many hams choose to do most of their operating from their automobile during commute times, using a magnetic mount antenna connected to an under-dash transceiver or a hand-held radio.
Ham radio station in automobile
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Power Output
Depending on the size (hand-held or desktop), power can be from a few milliwatts to 1,500 watts. Many new hams are graduates from citizens band (CB) radio. Unlike the 5-watt limit on CB, hams can use quite a bit more power (1,500 watts).
The ham radio can fit in your shirt pocket, take up half of an attic or garage, sit on a desk next to the computer or go into a car. Right now, during the current sunspot cycle, it is possible to talk around the world during daylight hours running just a few watts of power. This particular type of radio-wave propagation is in the 28-MHz band (commonly called the 10-meter band) thanks to short-wave propagation (300 divided by the frequency in MHz is a quick way to convert to "meters").
Antennas
Little whip antennas, wire antennas in trees, and antennas atop a tower are all used, depending on the frequency in use. Lower frequencies have longer wavelengths. Longer wavelengths need larger antennas. The same antennas (used to transmit and receive) can be small, portable, put in trees or on the trunk of a car.
Short-wave antenna
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The common 146-MHz (2-meter) antenna is a 19-inch quarter-wave whip. A wavelength at 146 MHz is approximately 2 (300 divided by 146) meters, and a quarter wave of 2 meters is about 19 inches (50 cm). Hams enjoy the fun of experimenting with various types of antennas. Some antennas are made of wire strung between trees. Be sure to use lightning protection for outside antennas!
Hams, including the writer of this article, have communicated with other hams using the following types of antennas with antenna tuners:
- Metal window screens in upper floors of hotels and motels
- Aluminum extension ladders, insulated from the ground, leaning against a house (the lower the frequency, the longer the ladder)
- Soldered-together rain gutters and downspouts
- Flat copper "burglar-tape" hidden behind wallpapered walls
- Extended "Slinky" toys supported by a rope through the middle, in an attic
- Camera-tripod-supported whip antenna
- Disguised flagpoles fed with buried coaxial cable
- Fine wires cast with a fishing rod between dormitory buildings
What keeps ham operators from transmitting on the same frequency?
Many hams can be on the same frequency, but it depends on the propagation factors. VHF and UHF are line-of-sight, so many hams can be on the same frequency in one state. On short-wave bands, radios have variable frequency tuning to allow moving your transmitted signal (in very small increments) in between two other transmitting stations. Hams often do a lot more listening than transmitting. Often, they listen for another ham that identifies the station as being in a sought-after county, state, or country.
This LCD on a modern transceiver is displaying the spectrum of nearby stations. The band-scope at the bottom helps ham operators find signals.
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Hams collect confirmations of contacts using QSL cards. Hams collect the QSL cards and receive awards for contacting so many countries on certain frequency bands. VHF and UHF hand-held radios typically use channeled communications, using selectable fixed frequencies.
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