How Ham Radio Works
by Gary Brown
A teen in Florida makes friends over the
airwaves with a ham in Germany.
An aircraft engineer in Washington participates in an annual
contest and exchanges call signs with hams in 100 countries during a
single weekend. In North Carolina, volunteers pass health and welfare
messages in the aftermath of a hurricane.
Norm Lauterette, WA4HYJ, is on the radio reporting a
new flare up during the wildfires that broke out in several counties in
Florida during June and July of 1998.
|
At the scene of a traffic
accident on a rural highway, a ham calls for help by using a
pocket-sized hand-held radio, outside the range of any
cell phone
tower. An Ohio teenager uses her computer to send a
chess
move to an
orbiting space satellite, where it's retrieved by a fellow chess enthusiast in
Japan.
This mix of fun, public service, friendship, and convenience is the main feature of
Amateur Radio. The "ham" part of ham radio is really a shortcut way of saying only the first syllable of
amateur radio. Hams start out in amateur radio for many reasons, but they all
have in common a basic knowledge of radio technology, regulations and operating principles.
They get this knowledge by studying for licensing exams -- Hams have licenses (after passing an exam) from the Federal Communications
Commission (FCC) and use frequency bands assigned by the FCC.
In September 1895, Guglielmo Marconi, a self-taught 21-year-old from Bologna,
Italy performed simple experiments that showed it was possible to send signals
by using electromagnetic waves to connect a transmitting and a receiving antenna.
By 1901, he sent a wireless signal across the Atlantic. For the next seven years,
many Americans experimented with wireless. The first radio clubs appeared in 1909,
and the Titanic disaster of 1912 pointed out the need for regulation of wireless.
Today, ham radio operators younger than Guglielmo Marconi regularly make radio
contacts around the world, often using very inexpensive (and sometimes home-made)
equipment!
Today, ham radio can be very portable and affordable. In
this edition of How Stuff Works we will look at ham radio
and show you how to get started in this wireless world!
Why Would I Get Into Ham Radio?
Ham radio is for anyone who likes to communicate with others via wireless
technology. It is also for anyone who enjoys experimentation.
Licensed amateur radio operators communicate with each other in nearby places,
across the country, around the world or even with astronauts in outer space!
Young operator enjoys
making friends over the radio during Kid's Day. Kid's Day is an annual event
that encourages young people to get on the
air, perhaps with a family member or a neighbor who is a licensed Amateur
Radio operator.
|
Amateur radio is a worldwide group of people who communicate with
each other over a wide
frequency spectrum
using many different types of wireless transmitting modes.
Often, younger hams get a chance to meet other hams of various ages and
professions. The frequent networking often helps a teen when they are making
career or education choices and wish to get some advice (from professionals
in many technical fields) that maybe mom, dad, or the guidance counselor may not have.
How Many Licensed Ham Radio Operators Are There?
Today, there are approximately 675,000 Amateur Radio operators in the
United States and more than 2.5 million around the world. To find out how
to get started and who to contact in your area, call or write the non-profit organization:
American Radio Relay League
225 Main Street, Newington, Conn., 06111. Telephone:
1-800-32NEW HAM.
What Frequencies and Transmitting Modes Do Hams Use?
Hams use a
variety of frequencies
for communications.
Non-hams can "listen in" via their own receivers or radio scanners.
Hams are able to use many frequency bands across the radio spectrum -- these frequencies are allocated by the FCC for amateur use.
Hams may operate from just above the AM broadcast band to
the microwave region, in the gigahertz range. Many ham bands are
found in the frequency range that goes from above the AM radio band (1.6 MHz)
to just above the Citizen's Band (27 MHz). During daylight, 15-27 MHz is a
good band for long-distance communications. At night, the 1.6-15 MHz band is good
for long distance communications. These bands are often referred to historically as short-wave bands (as in "short-wave radio").
Unlike frequencies used by FM radio stations and TV stations,
which are line-of-sight and therefore limited to 40 or 50 miles, short-waves "bounce" off the ionosphere
from the transmitter to the receiver's antenna. The higher the frequency is,
the "shorter" the wavelength is.
Some ham radio operators use the very reliable
Morse code,
while others use voice. Morse code signals (beeps) often get through when voice transmissions
cannot.
There are also very many digital modes as well,
and hams use radio modems to communicate in various networks.
What Are the Varieties of Ham Radio Activities?
Computer-Assisted Radioteletype
|
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.
Instead, hams conduct two-way conversations often with another ham,
or a group of hams in an informal "roundtable." The roundtable of hams may be in the
same town, county, state, country or continent or 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,
with computer screens replacing the noisy teletype
machines of the past.
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.
|
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 an uplink (receiver) at 145.975 MHz and simultaneously rebroadcasts (downlink) at
435.070 MHz for one station at a time, as a repeater.
Ham Radio Station in Automobile
|
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.
In each of the recent 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 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.
What are the License Requirements?
You need an easy-to-earn license to transmit on an amateur radio frequency.
License tests cover electronics theory and amateur radio rules and regulations.
Study guides are readily available. There is no age restriction. Each country has
its own licensing arrangements. Many countries share many of the same frequency
bands with hams in the U.S. Each license class allows operation in certain bands, using
certain modes. The higher the class of license, the more allowable frequency bands that
are available for use.
Recently the FCC relaxed the Morse Code requirements portion of the rules to make
it easier to get an amateur radio operator's license. The FCC's new licensing plan
means you will be able to become a ham by passing a single 35-question written
examination. License study guides are readily available for the written test.
The American Radio Relay League (ARRL)
helps many get into amateur radio. The ARRL was organized in 1914 by H.P.
Maxim to help relay radio messages. Most radio messages had a 25-mile range
at that time and were transmitted around 1.5 MHz, at the high end of the
AM broadcast band. The ARRL has many useful publications. Local volunteers
around the country administer Amateur Radio tests. These volunteers are usually
members of an amateur radio
club.
What Are the Amateur Radio Operator Exams Like?
Under the recent new licensing scheme, there are four examination elements:
- Element 1 -- 5 words per minute (WPM) Morse code exam
- Element 2 -- 35-question written test to obtain a Technician license
- Element 3 -- 35-question written test to obtain a General license
- Element 4 -- 50-question written test for the Amateur Extra license
The written tests consist of multiple choice exams. Online study guides
are on the Internet or you can buy them. Each type of license has
specific operating privileges on each
ham band.
What Kind of Equipment Would I Typically Start With?
Vintage Tube-Type Short-Wave Receiver
|
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. 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.
What Is the Power Output of an Amateur Radio?
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, set 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")
What Kind of Antenna Does An Amateur Radio Need?
Short-Wave Antenna
|
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 lid of a car.
The common 146 MHz (2-meter) antenna is a 19-inch quarter-wave whip.
A wavelength at 146 MHz is approximately two (300 divided by 146) meters, and a
quarter wave of two 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?
LCD on modern transceiver, with spectrum displayed of nearby stations.
The band-scope at the bottom helps ham operators find signals.
|
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 being in a sought-after county, state, or
country. 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.
What is a Hamfest?
There are frequent hamfests, or ham radio fleamarkets
in many areas. Hamfests are the best place to meet hams, buy equipment,
and take your license test. It's a great way to find some terrific deals
on used equipment. You will also find computer parts at hamfests.
Hamfests often offer license tests, too. It is relatively inexpensive to
get into amateur radio if you learn how to shop for used equipment with
the aid of someone at a local radio club. Think of a hamfest as a real-time,
in-person ham radio display usually found at
EBay
without having to bid against others!
Look for a transceiver with a built-in general coverage receiver.
That way you get the versatility of two hobbies: ham radio and short-wave listening.
Each May, the
world's largest ham radio convention-hamfest
is held in Dayton, Ohio.
How Do I Get Started in Amateur Radio?
- Listen in on the
Amateur Radio Frequency Bands (U.S.)
via a
radio scanner,
or a short-wave receiver.
Be sure any short-wave receiver you buy is cable of receiving single
sideband (SSB) used for voice communications on the short-wave bands.
On any scanner, you will hear local ham operators using repeaters in the
frequency range of 144 to 148 MHz.
- Read the information in the various links at the end of this article.
- Most important: find a ham and talk to one. We love to talk about
fun and experiences in amateur radio and are known for being an
"Elmer"
(teacher) for those new to
amateur radio. When you hear a ham's call sign on your receiver or scanner,
look up,
the ham's
call sign to find a way to contact that ham!
Who knows, maybe someday your next ham radio contact may be
music entertainers such as Ronnie Milsap, Patty Loveless, or Joe Walsh -- they are
all FCC-licensed amateur radio operators!
Links
American Radio Relay League Resources For New Hams
Getting Started
What Hams Do
Getting Your License
Frequencies Hams Use
Where Hams Shop
More Links
Photographs and assistance
provided by the American Radio Relay League, Reed-AB4W, Bob-K4HA, and Gary-KN4AQ.
About the Author
Gary Brown-K4GPB is an
editor and writer for HowStuffWorks.com. He has been licensed since
1961, and operates primarily 40 meter single sideband (SSB) when he's not
radio scanning.
