Saturday, May 31, 2014

Historical Events in Amateur Radio

Guglielmo Marconi
1894-1899-- Marconi conducts his wireless experiments in Europe and sends a message across the English Channel.

1901-Marconi sends a wireless signal across the Atlantic.

1900-1908--Thousands experiment with wireless. Few at this time are interested in it as a hobby only.

1904-J.A. Fleming develops the 2 element (Diode) vacuum tube.

1906-Lee deforest develops the 3 element (Triode) vacuum tube. R.A. Fessenden uses the Alexanderson Alternator to make the first voice & music transmissions.

1908-A possible beginning of amateur radio. Prior to this time, interest in wireless had primarily been either as an experimenter or as an entrepreneur. By 1908, definite hobby interests exist among users.

1909-The first radio clubs are formed. Spark and the long-waves (300-6000 meters)

1912-The Titanic disaster points out the need for Wireless Regulation. The Radio Act of 1912 is passed, which limits amateur radio stations to 200 meters.

1913-Edwin Armstrong develops the regenerative receiver and also discovers that the "Audion" (Triode) can oscillate. CW is born.

1914-The ARRL is organized by H.P. Maxim to help relay messages, given the limited range on 200 meters at that time. (25 miles).

1914-1917--The number of amateur radio stations increases. The ARRL starts a little magazine, called "QST".

1918-Major Armstrong develops the superheterodyne receiver while serving in France. C.W. is used by the military during the war.

1919-Secretary of the Navy Josephus Daniels tries to get the Navy a total monopoly on all wireless communications.

1920-"Amateur Police Radio" becomes popular. Amateurs operated as an intersystem police communications service to relay broadcasts of crimes and stolen vehicles.

1921-1922--The National Amateur Wireless Association becomes active. It's main success is the broadcast of the Dempsey-Carpenter fight. Many amateurs helped in this broadcast, from acting as relay stations to setting up receivers and loudspeakers in public places.

1923-The amateur radio census is at 12,000. Shortwave development continues.The MacMillan Arctic Expedition is the first to carry two way radio; an amateur 200 meter station.

1924-Amateur radio get new bands at 80, 40, 20, and 5 meters. Spark prohibited on the new bands.

1925-The International Amateur Radio Union (IARU) formed 1925.

1926-Radio Act of 1912 to be unenforceable in regards to broadcasting & the Shortwave radio.

1927-The Radio Act of 1927 creates the Federal Radio Commission.

1929-1936--Despite the Depression, Amateur Radio, low cost components make it possible to build a quality station . VHF phone operation becomes popular with the superregenerative receiver (developed by Armstrong) and the modulated oscillator. Phone operation begins to appear on some HF bands. But C.W. & crystal control are still number one.

1933-1934--The Communications Act of 1934 creates the Federal Communications Commission. Amateur radio Licenses are reorganized into Class A, Class B, and Class C. Major Edwin Armstrong develops wide-band FM.

1936-H.P. Maxim, founder of the ARRL & it's first President, dies.

1938-The Cairo Conference. Amateur radio lose the exclusive use of 40 meters, now shared with Broadcasters. The FCC gives us 2 new "UHF" bands, 2 1/2 meters (112 Mc) and 1 1/4 meters.

1939-1940--We are joined in the "UHF" range by two new users--the first FM Broadcast Band .

1942-1945--Except for the War Emergency Radio Service on 2 1/2 meters, no amateur radio operations take place. New "UHF" tubes and circuits are developed as a result of the war.

1945-A major battle develops over postwar frequency allocations. Major Armstrong (FM Broadcasting), and Brigadier General David Sarnoff (RCA/NBC Television), all fight over the low end of the VHF spectrum between 44-108. At one point, the FCC submits 3 Alternatives--one gives us a 7 meter band , two our 5 meter band , and three a 6 meter band . 6 meter band  wins and  is located between TV Ch 1  and Ch 2 .The FCC moves our 2 1/2 meter band to 144-148 MHz.

On November 15, 1945, amateurs are allowed back on the air--but just on 10 & 2 meters only. 1945-CQ magazine is first published.

1946-The military leaves our HF bands in stages, amateur radio operators gradually get their frequencies back, all except for 160 meters, which will be used for the LORAN Radio navigation system. The FCC creates the Tenth Call District (using the numeral -0-), and realigns the District boundaries. War surplus equipment finds its way into the ham radio market.

1947-The Atlantic City Conference--Amateurs lose the top 300 kc of 10 meters , and will lose 14.35--14.4  on 20 meters. But they will gain a new band at 15 meters  in the future. To compensate ham radio for their loss, the FCC allows them to use the 11 meter band on a shared basis with Industrial, Scientific & Medical devices. TVI is starting to become a problem--the ARRL determines that Ch 2 is very vulnerable to TVI & recommends it be eliminated, but the FCC removes Ch 1 instead. The Transistor is developed by Bell Labs.

1948-Single Sideband is fully described in the amateur radio publications.

1951-The FCC completely reorganizes the amateur license system. The Class A, B, & C Licenses are replaced by the Advanced, General, & Conditional Class respectively. Three new license classes are created--the Amateur Extra, Novice & Technician. The Technician Class is created for experimentation, not communication, and has privileges only above 220 MHz Novices are given limited HF CW sub-bands, 75 watts, crystal control only. They may also use phone on 145--147 MHz It is a one year, non renewable license.

1952-The FCC allows phone operation on 40 meters, which had been CW only. The 15 meter band is opened. The Advanced Class is withdrawn from new applicants, although present holders can continue to renew, and the "exclusive" 75 & 20 meter phone bands are opened to Generals & Conditionals. Everyone, Conditional & above, has the same privileges.

1953-The FCC starts issuing "K" calls to amateur radio operators in the 48 States due to the increased ham radio population.

1954-Depressed and broke from his patent fights with RCA over FM, Major Edwin Armstrong commits suicide. His wife continues the fight, winning the last battle in 1967, when the Supreme Court rules that Armstrong did indeed invent FM.

1955-Technicians are given 6 meter privileges to help populate the band & encourage experimentation. The ARRL & most ham radio operators oppose 2 meters for Technicians. Wayne Greene becomes editor of CQ magazine.

1956-1960--A gradual technical revolution on 2 fronts: Transistors find their way into the ham radio shack, first in power supplies, then audio sections, then receivers and finally QRP transmitters. But most equipment was still 100% tubes. Also, SSB is catching up on AM in terms of popularity. By the 1960's, SSB pulls ahead of AM.

Sputnik artificial satellite
1957-Sputnik, the first artificial satellite, is launched by the USSR. Amateurs copy it's beacon on 20 & 40 Mc.

1958-Explorer is launched by the US. Amateurs copy it's signal on 108 Mc. The ham radio population is 160,000--3 times the 1946 total. The FCC has to issue "WA" calls in the 2nd & 6th call areas, as the "W" & "K" 1x3 prefixes have run out. Slow Scan TV is first described in QST. In September, amateurs lose their shared use of 11 meters, as Class D CB is born.

1959-The Geneva Conference held, no major amateur changes. Technicians get the middle part of 2 meters (145-147 Mc), but not without some controversy over the purpose of the license. The FCC restates their "experimental, not communication" policy.

1960-Wayne Greene fired as CQ editor, forms 73 magazine.

1961-OSCAR I, the first amateur radio satellite, is launched. Thousands of Amateurs copy it's 50 mw beacon on 144 Mc.

1962-CONELRAD is replaced by the Emergency Broadcast System. Amateurs no longer have to monitor 640 or 1240 kc while operating their stations.

1963-The ARRL, responding to some complaints about Generals being allowed on 75 & 20 phone, proposes an "incentive licensing" system. Under the ARRL proposal, Generals & Conditionals would lose 75, 40, 20 & 15 meter phone privileges over a 2 year period. The Building Fund, to construct the ARRL Headquarters at 225 Main St., Newington, is in full swing. The amateur radio population is over 200,000, but CB licenses now outnumber hams.

President Herbert Hoover
1964-Herbert Hoover dies at the age of 90. As Secretary of Commerce in the 1920's, and President of the United States from 1929-1933, his strong support of amateur radio was invaluable. He lived long enough to see his son (Herbert Hoover, Jr, W6ZH) elected President of the ARRL.

1965-The FCC comes out with it's own incentive licensing proposal.

1969 -The FCC removes the ability for a Technician to hold a Novice license at the same time. The ARRL announces a new policy, they now consider Technicians to be communicators and petition the FCC to give them full VHF privileges, a 10 meter segment from 29.5-29.7 Mc, and Novice CW sub bands.

1970-The amateur radio population is 250,000 but stagnant.2 meter FM is starting to boom. New equipment designed for the amateur radio market joins the surplus wide band commercial radios which were converted for use on 146.94. "Mhz" & "khz" replace "Mc" & "kc".

1972-A national 2 meter FM band plan was announced,146.52 MHz was chosen as the national simplex frequency.

1974-The Electronics Industry Association proposed a new "Class E CB" using 2 MHz of our 220 band.

1975-1976--A new repeater sub band is established at 144.5-145.5 MHz.Technicians now have 144.5-148 MHz on 2 meters, and finally have Novice privileges. Novices are given a power increase to 250 watts. The "mail order" Technician license is eliminated--applicants must appear at a FCC examination site.

1977-The FCC expands CB radio from 23 to 40 channels. Hundreds of hams purchase "obsolete" 23 channel CB sets at fire sale prices and convert them to 10 meters.

1978-Technicians finally get all privileges above 50 MHz, and can obtain a RACES Station authorization. The amateur radio population stands at 350,000. "Packet" radio first appears on the ham bands, on an experimental basis.

1979-The World Administrative Radio Conference, or WARC-79, takes place in Geneva. The ARRL, IARU & other groups have been preparing for years.

1980-Spread Spectrum appears on an experimental basis, and the FCC authorizes ASCII on the ham radio bands.

1983- Owen Garriott, W5LFL, becomes the first amateur radio operator to be on board a Space Shuttle. He makes hundreds of QSO's on 2 meters.

1984-The FCC stopped giving examinations, turning the duty over to the new Volunteer Examiner Program. . The amateur radio population is up to 410,000.

1987-Novices & Technicians get 10 meter SSB privileges from 28.3-28.5 MHz Novices also get phone operation on portions of 220 & 1296 MHz The Element 3 written exam is broken into 2 segments--3A (Technician) and 3B (General). Technicians who passed their exam prior to March 1987 get permanent credit towards the General written exam.

1990-1991--MARS (military affiliate radio network) operations increased as amateurs became involved in Operation Desert Shield/Storm. Tens of thousands of Americans discover Shortwave Radio, to get the latest news.

1991-Amateur Radio gets it's first code free license--the "No Code Technician". "Regular" Technicians are renamed "Technician Plus". The first all amateur Shuttle, the "Atlantis", goes into space.

1991-1998--Amateur Radio grows from 500,000 to over 710,000.

Copyright 2011 by The Ham Radio Files.
All rights reserved. ツ

Listening on Amateur Radio Bands

Amateur Radio Bands Most of the traditional shortwave bands between 1.8 and 30 MHz are broadly
organized into two segments. Digital transmissions such as CW (Continuous
Wave, meaning, Morse code), radio teletype
(or RTTY), and data occupy the
lower segment. Voice signals occupy the higher segment. Within each of these
segments, the lower frequencies are where you tend to find the long-distance
(or DX) contacts, special-event stations, and contest operating. Casual conversations,
known as ragchews, and scheduled on-the-air meetings (nets) generally take place on the higher frequencies within each band.

Depending on which activity holds your interest, start at one edge of the listed frequency ranges and start tuning. While tuning, use the
widest filters your radio has for the mode (CW, SSB, or FM) that you select.

If every voice you hear seems scrambled, your rig is probably set to receive
the wrong sideband. Change sidebands and try tuning again.
Because the ionosphere strongly affects the signals on the HF bands as they
go from point A to point B, the time of day makes a big difference. On the lower
bands, the lower layers of the ionosphere absorb signals through the day, but
disappear at night, allowing signals to reflect off the higher layers and reflect
over long distances. Conversely, the higher bands require the sun’s illumination
for the layers to reflect HF signals back to Earth, supporting long-distance
hops or skips.

Single-Sideband (SSB)

Single-sideband (SSB) is the most popular mode of voice transmission on the
HF bands. (FM is mainly used above 50 MHz) The mode got its name because
of a key difference from the older mode, AM, which is used by AM broadcast
stations and was the original voice mode hams used. Whereas an AM transmitter
outputs two identical copies of the voice information, called sidebands,
a SSB signal only outputs one. This signal is much more efficient and saves
precious radio spectrum space.

Most voice signals on HF are SSB, so you have to choose between USB (Upper
Sideband) and LSB (Lower Sideband). The actual SSB signals extend in a narrow
band above (USB) or below (LSB) the carrier frequency displayed on the radio
(see Figure 8-2). How do you choose? By long tradition stemming from the
design of the early sideband rigs, on the HF bands above 9 MHz, voice operation
is always on USB. Below 9 MHz, you find everyone on LSB.

Because hams must keep all signals within the allocated bands, you need
to remember where your signal is actually transmitted. Most voice signals
occupy about 3 kHz of bandwidth. If the radio is set to USB, that means your
signal appears on the air from the displayed frequency up to 3 kHz higher.
Similarly on LSB, the signal appears up to 3 kHz below the displayed frequency.
When operating close to the band edges, make sure your signal stays in the
allocated band. For example, on 20-meters, the highest frequency allowed for
hams is 14.350 MHz You can tune a radio operating on USB no higher than
14.350 MHz -3 kHz = 14.347 MHz to stay legal.


Ham Radio License Plates

You can also acquire a license plate with your call sign. The process is easy and many states even have a special type of vanity plate just for hams. Contact your local Department of Motor Vehicles and ask! For additional information see

The Amateur Radio Service

By international treaty, the Amateur Service in every country is a  licensed service. That is, a government agency has to approve the application of every ham to transmit. It allows amateurs to communicate internationally and directly, without using any kind of intermediate system that regulates their activities. Because of the power and scope of Amateur Radio, hams need a minimum amount of technical and regulatory background so they can coexist with other radio services, such as broadcasting.

By maintaining the quality of licensees, licensing helps ensure that the
Amateur Service makes the best use of its unique citizen access to the airwaves.
Amateur Service sets ham radio apart from the unlicensed services
and is recognized in the FCC rules as the Basis and Purpose of the Amateur
Radio Service, rule 97.1:

Recognition of ham radio’s exceptional capability to provide emergency
communications (rule 97.1(a))

Promote the amateur’s proven ability to advance the state of the radio
art (rule 97.1(b))

Encourage amateurs to improve their technical and communications
skills (rule 97.1(c))

Expand the number of trained operators, technicians, and electronics
experts (rule 97.1(d))

Promote the amateur’s unique ability to enhance international goodwill
(rule 97.1(e))

You can find all the rules for Amateur Radio at

Feedline and Measurements


Most radios and antenna tuners have the ability to evaluate the electrical conditions inside the feed line, measured as the standing wave ratio (SWR).

SWR is a ratio of voltages and tells you how much of the power supplied by the transmitter is getting radiated by the antenna. Most radios have a built-in meter that shows feed line SWR. Having a stand-alone SWR sensor, called an SWR meter or an SWR bridge, to measure SWR is very handy when working on antennas or operating in a portable situation. You can also measure feed line conditions by using a power meter, which measures the actual power flowing back and forth. SWR meters are inexpensive, while power meters are more accurate. These devices are typically used right at the transmitter output.

Feed lines
Two common types of electrical feed lines connect the antennas to the station
and carry RF energy between pieces of equipment. The most common is coaxial
cable, or just coax, so named because it is constructed of a hollow tube surrounding central wire concentrically. The outer conductor is called the shield and also braid, if made from fine woven wire. The wire in the middle is called the center conductor and is surrounded by insulation that holds it right in the center of the cable.The outer conductor is covered by a plastic coating called the jacket. The other kind of feed line is open-wire, also called twin-lead or ladder line, which is made from two parallel wires. The wires may be exposed, only held together with insulating spacers, or plastic insulation may cover them.

The Basic Ham Radio Station and accessories

The Radio Spectrum

The different users of the radio spectrum are called services, such as the broadcasting service or Amateur Radio Service. Each service gets a certain amount of spectrum to use, called a frequency allocation. Amateur Radio, or ham radio, has quite a number of allocations sprinkled throughout the radio spectrum.

Radio waves at different frequencies act differently in the way they travel and require different techniques to transmit and receive. Because waves of similar frequencies tend to have similar properties, the radio spectrum is divided
into four segments:

Shortwave or High-Frequency (HF): Frequencies below 30 MHz
Includes AM broadcasting, ten different ham radio bands, ship-to-shore
and ship-to-ship, military, and Citizens Band.

Very High Frequency (VHF): Frequencies from 30 to 300 MHz Includes
TV channels 2 through 13, FM broadcasting, three ham bands, public
safety and commercial mobile radio, and military.

Ultra High Frequency (UHF): Frequencies from 300 MHz to 1 GHz.
Includes TV channels 14 and higher, two ham bands, cellular phones,
public safety and commercial mobile radio, and military.

Microwave: Frequencies above 1 GHz. Includes GPS, digital wireless telephones,Wi-Fi wireless networking, microwave ovens, eight ham bands, satellite TV, and numerous public, private, and military users.

Frequency and Wavelength

If you know a radio wave’s frequency, you can figure out the wavelength because the speed of light 300,000,000 ( kilometers per second), is always the same. Here’s how:

Wavelength = Speed of light / Frequency of the wave Wavelength in meters = 300,000,000 / Frequency in hertz

Frequency in hertz = 300,000,000 / Wavelength in meters
Frequency is abbreviated as f, the speed of light as c, and wavelength as the Greek letter lambda, λ, leading to the following simple equations:

f = c / λ and λ = c / f

Examples:   300,000,000 (c) /1800 kHz (f) =166 Meters
                    300,000,000 (c) /148,000 MHz (f) =2 Meters
                    300,000,000 (c) /50.000 MHz (f) =6 Meters

Radio waves oscillate at frequencies between a few hundred kilohertz, or kHz
(kilo is the metric abbreviation meaning 1,000), up to 1,000 gigahertz, or GHz
(giga is the metric abbreviation meaning 1 billion). They have corresponding
wavelengths from hundreds of meters at the low frequencies to a fraction of a
millimeter (mm) at the high frequencies. The most convenient two units to use in thinking of radio wave frequency (RF) and wavelength are megahertz (MHz; mega means 1 million) and meters (m).

f = 300 / λ in m and λ = 300 / f in MHz

Fundamentals of Radio Waves

Radio waves are just another form of light and travel at the same speed: 186,000 miles per second. Radio waves can get to the moon and back in 21⁄2 seconds or circle the Earth in 1⁄7 of a second.
An electric field and a magnetic field carry the energy of a radio wave.

These fields affect charged particles, such as the electrons in a wire, and make them move. Electrons move in specific ways: They move parallel to electric fields and in circular motions in response to magnetic fields. These moving electrons (that is, current) also create moving electric and magnetic fields.

Transmitters cause electrons to move so that they, in turn, create the moving
fields of radio waves. Antennas are just structures for electrons to move in to
create radio waves. The electrons in an antenna also move in response to
radio waves launched by other antennas. Receivers then detect the electron
motion caused by the incoming radio waves. The energy is just transferred
from electrons to radio waves and back to electrons at the other station.

Building a Ham Radio Shack

The term radio shack, is simply the place
you keep your radio and ham equipment.
For some hams, the entire shack consists of a hand-held radio or two. Other hams operate on the go in a vehicle. Cars make perfectly good shacks, but most hams have a spot somewhere at home they claim for a ham radio.

Here’s what you can find in a ham shack:

The rig: The modern radio or rig combines both in a single, compact package about the size of a large DVD player. Like its ancestors, a large tuning knob controls the frequency. Unlike them, state-of-the-art digital displays replace the
dials and meters.

Computer: A majority of hams today have at least one computer in the
shack. Computers now control many radio functions (including keeping
records). Using digital data communications simply wouldn’t be possible
without one. Some hams use more than one computer at a time.

Mobile/base rig: For operating on the local repeater stations, hams may
use a hand-held radio, but in the shack a more capable radio is used.
These units are about the size of a good-sized hardcover book and you
can use them as either a mobile or base rig.

Microphones, keys, and headphones: Depending on the shack owner’s
preferences, you see a couple (or more!) of these important gadgets, the
radio’s true user interface. Mikes and keys range from imposing and
chrome-plated to miniaturized and hidden. The old Bakelite headphones
or cans are also a distant memory , replaced with lightweight and comfortable, hi-fi quality designs.

Antennas: In the shack, you find switches and controllers for antennas
that live outside the shack. Outside, a ham shack tends to sprout antennas
ranging from vertical whips the size of a pencil to wire antennas
stretched through the trees and on up to super-sized directional beams
held high in the air on steel towers.

Cables and feed lines: Look behind, around, or under any piece of shack
equipment and you find wires. Lots of them. The radio signals pipe
through fat, black round cables called coaxial (coax).

Friday, May 30, 2014

Ham Radio DX-ing, contests, and awards

DX stands for distance and the lure of making contacts ever-farther from home has always been a part of ham radio. Hams compete to contact faraway stations and to log contacts with every country. They enjoy contacting islands and making personal friends in a foreign country.

Ham radio contests are events in which the point is to make as many contacts as possible, sometimes thousands, during the contest time period, by sending and receiving short messages. These exchanges are related to the purpose of the contest — to contact a specific area, use a certain band, find a special station, or just contact everybody.

Along with contests, thousands of special-event stations and awards are
available for various operating accomplishments, such as contacting different
countries or states.

Making Contacts in Ham Radio

If you were to tune a radio across the ham bands, what would you hear ham radio operators doing?


By far the most common type of activity for ham radio operators is just engaging in conversation, which is called chewing the rag; such contacts are called ragchews. Ragchews take place between continents or across town. You don’t have to know another ham to have a great ragchew.

Nets: are organized on-the-air meetings scheduled
for hams with a similar interest or purpose. Some of the nets you can
find are

Traffic nets: These are part of the North American system that moves
text messages or traffic via ham radio. Operators meet to exchange or
relay messages, sometimes handling dozens in a day. Messages range
from the mundane to emergency health-and-welfare.

Emergency service nets: Most of the time, these nets just meet for training
and practice. When disasters or other emergencies strike, ham radio operators organize around these nets and provide crucial communications.

Technical Service: These nets are like radio call-in programs in which
ham radio stations call with specific questions or problems. The net control station may help, but more frequently, one of the listening stations contributes
the answer.

ALE Mailboxes and Bulletin Boards: Instead of transmitting 1s and 0s as voltages on wires, hams use tones.ALE stands for Automatic Link Establishment and means that a computer system is monitoring a frequency all the time so that others can connect to it and send or retrieve messages. Sailors and other travelers use ham radio where the Internet isn’t available.

Swap Nets: In between the in-person ham fests and flea markets, in many
areas a weekly swap net allows hams to list items for sale or things they
need. A net control station moderates the process and business is generally
conducted over the phone once the parties have been put in contact
with each other.

Ham Radio using Electronics and Technology

Ham radio operators also develop their own software and use the Internet along with radios to create novel hybrid systems. Hams developed packet radio by adapting data transmission protocols used over computer networks to amateur radio links. Packet radio is now widely used in many commercial applications. By combining GPS radiolocation technology with the Web and amateur mobile radios, the Automatic Position Reporting System (APRS) was developed and is now widely used.

Voice and Morse code communications are still the most popular technologies
by which amateur radio operators talk to each other, but computer-based digital operation is gaining fast. The most common home station configuration today is a hybrid of the computer and radio. Some of the newer radios are exploring software defined radio (SDR) technology that allows reconfiguration of the circuitry that processes radio signals under software control.

Along with the equipment and computers, hams are students of antennas and
propagation, which is the means by which radio signals bounce around from
place to place. Amateur radio operators take an interest in solar cycles, sunspots, and how they affect the Earth’s ionosphere. For hams, weather takes on a whole new importance, generating static or fronts along which radio signals can sometimes travel long distances. Antennas, with which signals are launched to take advantage of all this propagation, provide a fertile universe for the station builder and experimenter.

Antenna experimentation is a hotbed of activity for ham radio operators. New designs are created every day and hams have contributed many advances and refinements to the antenna designer’s art. Antenna systems range from small patches of printed circuit board material to multiple towers festooned with large rotating arrays. All you need is some wire, a feed line, and a soldering iron.

Amateur radio operators  also use radio technology in support of hobbies such as radio control (R/C), model rocketry, and meteorology. Amateur radio operators  have special frequencies for R/C operation in the 6-meter band, away from the crowded unlicensed R/C frequencies. Miniature ham radio video transmitters are frequently flown in model aircraft, rockets, and balloons, beaming back pictures from heights of hundreds and thousands of feet. Ham radio data links are also used in support of astronomy, aviation, auto racing and rallies, and many other pastimes.

Amateur Radio Communications Theory

Sky-wave propagation- A type of radio-wave propagation in which
radio waves traveling upward are bent or refracted by the ionosphere back to the earth. This is one of the major means of amateur radio communication in the high-frequency spectrum. Otherwise, these radio waves would be propagated into outer space and lost. Sky-wave propagation provides a capability for long-range or DX communications using one or more “hops” in which the radio waves are reflected back to the earth.

Ground-wave propagation- Another form of propagation in which
the ground or surface wave travels along the surface of the ground or
water. This mode of propagation is important at the low and medium
frequencies. Most commercial AM broadcast stations use ground-wave
propagation during daylight hours for local urban and suburban coverage.
However, beginning at about 3 MHz, ground-wave propagation at distances greater than 100 miles (or about 160 kilometers) becomes impractical.

Refraction of radio waves- Radio waves, like light waves, are
refracted or bent when they pass from one medium to another medium
with a different density. Since radio waves traveling upward experience
less atmospheric density, they may be curved or bent. This is related to sky-wave propagation.

Sunspot cycle- The sun exhibits a periodic 11-year cycle of increasing and decreasing sunspots which affect radio communications on earth. Scientists have recorded the number of sunspots appearing on the surface of the sun for the past 300 years and have determined that the number of sunspots reaches a maximum about every 11 years. Also, the number of sunspots will vary during each maximum and minimum cycle. The maximums may range from about 60 to over 200 while minimums may drop to almost zero.

During maximum sunspot activity, excellent amateur communications
in the bands up to and including the 10-meter band are possible.
However, during minimum sunspot activity, long-range communication
is almost nil in the 15- and 10-meter bands. Also, 20-meter operation
is restricted primarily to daylight operation.

Skip distance- The skip distance is associated with sky-wave propagation
for the most part. It is defined as the distance between the transmitter
location and the point that the skywave returns to earth after striking the ionosphere. Except for the limited area subject to ground wave reception, the skip distance or zone does not allow for communications because no radio waves are reflected or bent into this zone.

Wavelength- The wavelength of a radio-frequency signal is defined
as the length in meters of that signal. More specifically, it is the length
of one complete cycle of the radio wave. Thus, a 10-meter signal or
wave is approximately 10 meters in length (or about 32.8 feet). For
example, a quarter-wave vertical antenna for 10 meters would be
approximately 2.5 meters (or about 8.2 feet) of vertical distance.

Frequency is defined as the number of complete cycles per second that a radio signal exhibits in passing from a value of maximum intensity, through zero intensity, and back to the original
value of intensity.

Frequency is measured in hertz (or simply Hz), which is directly equivalent to cycles per second; that is, 1 Hz equals 1 cycle per second.
Frequency is related to wavelength and may be used interchangeably to describe the wave motion of a radio wave. Frequency can be converted to wavelength in meters by dividing the frequency in hertz into 300,000,000. For example, 7150 kHz (which is 7,150,000 Hz) corresponds to a wavelength of 41.96 meters.

The ionosphere consists of layers of ionized air at heights above the surface of the earth ranging from about 7 to 250 miles (or about 11 to 402 kilometers). This ionization of the rarefied air particles is caused by the ultraviolet radiation from the sun. The heights of these layers vary from daylight to darkness, depending on the position of the sun with respect to the surface of the earth.

Daytime and Nighttime DX-ing

Daytime DX-ing

You must account for the fluctuations in the ionosphere when you’re DX-ing. Depending on the hour, the ionosphere either absorbs a signal or reflects it over the horizon. In the daytime, the 20, 17, 15, 12, and 10-meter bands, called the High Bands, tend to be “open” (support propagation) to DX stations.
Before daylight, signals begin to appear from the east, beginning with 20-meters and progressing to the higher bands over a few hours. After sunset, the signals linger from the south and west for several hours with the highest frequency bands closing first in reverse order. Daytime DXers tend to follow the Maximum Useable Frequency (MUF), the highest signal the ionosphere reflects. These reflections are at a very low angle and so can travel the longest distance for a single reflection (one reflection is called a hop) and have the highest signal strengths.
Nighttime DX-ing

From 30-meters down in frequency are the nighttime bands of 30, 40, 60, 80, and 160-meters, known as the Low Bands. These bands are throttled during the daytime hours by absorption in the lower layers of the ionosphere. After the sun begins to set, these bands start to come alive. First, 30, 40, and 60-meters may open in late afternoon and stay open somewhat after sunrise. 80 and 160meters, however, make fairly rapid transitions around dawn and dusk. Signals between stations operating on 80 and 160-meters often exhibit a short (15 to 30 minute) peak in signal strength when the easternmost stations are close to sunrise. This is known as the dawn enhancement. This time is good for stations with modest equipment to be on the air and take advantage of the stronger signals on these more difficult DX bands. 160-meters is known as Top Band because it has the longest wavelength of any current amateur band. This long wavelength requires larger antennas. Add in more atmospheric noise than at higher frequencies and you have a challenging situation. That’s why some of the most experienced DXers love Top Band DX-ing. Imagine trying to receive a 1 kilowatt broadcast station halfway around the world. That’s what the Top Band DXer is after! As difficult as this task sounds, many of the top DXers have managed it.

How to Build Amateur Radio Antennas

View RSS feed

Operating via Ham Radio Satellites

Non-ham radio operators are usually pretty surprised when you tell them about ham radio satellites. The first amateur radio satellite, OSCAR-1 (which stood for Orbiting Satellite Carrying Amateur Radio), was built by American hams and went into orbit in 1961, just a couple of years after the Russians launched the Sputnik satellite, igniting the space race. Today, hams have quite a number of satellites with missions ranging from digital mailboxes to repeaters to scientific experiments.

Satellite basics

Most amateur radio satellites are located in near-circular Low Earth Orbit, or LEO, circling the earth a number of times each day. A few have non-circular “Molniya” orbits that take them high above the earth where they are visible for hours at a time. (Molniya is “lightning” in Russian and is the name given to their fleet of communications satellites that travel in elliptical orbits.) For practical and regulatory reasons, satellite transmissions are restricted to the bands on 10-meters; on the 2-meter, 70-cm; and microwave bands at 1296 MHz and higher. The ionosphere usually does not pass signals at lower frequencies and satellite antennas need to be small, requiring shorter wavelength.

The input frequencies are called the uplink and the output frequencies are
called the downlink. The numbers that describe a satellite’s orbit (and allow
software to determine where it is) are called the orbital or Keplerian elements.
These pieces of information allow you to operate using a satellite!
You find three common types of satellites.

Transponder: These satellites listen on a range of frequencies on one
band, translate those signals to a different band, and then retransmit
them in real time.

Repeater: These satellites act just like terrestrial repeaters, listening and
receiving on a specific pair of channels. Satellite repeaters are crossband,
meaning their input and output frequencies are on different bands.

Digital: Digital satellites can act as bulletin boards (BBS) or as store-and forwardsystems. You can access both types of digital satellites using regular packet radio protocols and equipment. The International Space Station (ISS) and Space Shuttle (STS)  both have digital BBS systems available to hams on the ground. The ISS also has an APRS digipeater onboard! Store-and-forward satellites act as message gateways, accepting messages and downloading them to a few control stations around the world. The control stations also pass messages back up to the satellites that are downloaded by ground-based
users. Digital satellites are very useful to hams at sea or in remote locations.

Accessing the satellites

The best place to go to find out which satellites are active and in what mode
is the AMSAT home page ( Click the Satellite Frequencies
and Status link to get the complete set of information on what each satellite
does and its current operational status.

Thursday, May 29, 2014

Amateur Radio News

View RSS feed

HF Antennas

At HF, antennas can be fairly large. An effective antenna is usually at least 1⁄4-wavelength in some dimension. On 40-meters, for example, a 1⁄4-wavelength vertical antenna is a metal tube or wire 33 feet high. At the higher HF frequencies, antenna sizes drop to 8–16 feet, but are still larger than even a big TV antenna. Your physical circumstances have a great effect on what antenna you can put up. Rest assured that a large variety of designs are available to get you on the air.

Wires, verticals, and beams are the three basic HF antennas used by ham radio operators all over the world. You can build all these antennas with common tools or purchase them from the many ham radio equipment vendors.

Wire antennas

The simplest wire antenna is a dipole, which is a piece of wire cut in the
middle and attached to a feed line,  The dipole gives much better performance than you may expect from such a simple antenna. To construct a dipole, use 10- to 18-gauge copper wire. It can be stranded or solid, bare or insulated. When completed, its length should be:

Length in feet = 468 / frequency of use in MHz

This formula accounts for a slight shortening effect that makes a
1⁄2-wavelength of wire slightly shorter than a 1⁄2-wavelength in air. For example, a dipole for 21.1 MHz is 468 / 21.1 = 22.2 feet long. Allow an extra 18 inches on each end for attaching to the end insulators and tuning and another foot (6 inches × 2) for attaching to the center insulator. The total length of wire you need is 22.2' + 18" + 18" + 12" = 26.2'.

click to enlarge
To assemble a dipole, follow these steps:

1. Cut the wire exactly in the middle and attach one piece to each end
insulator, just twisting it back on itself for the initial check.
2. Attach the other end to the center insulator in the same way.
3. Attach the feed line at the center insulator and solder each connection.
4. Attach some ropes and hoist it up in the air.
5. Check the dipole.
6. If the SWR is low enough at too high a frequency or is lowest at the
high end of the band, loosen the connections at the end insulators and
lengthen the antenna by a few inches on each end.
7. When you adjust the antenna length so that the SWR is satisfactory,
make a secure wrap of the wire at the end insulators and trim the

If the frequency of lower SWR is too low, shorten the antenna by the
same amount.

Make some short, low power transmissions to measure the SWR
(standing wave ratio) as explained in your radio’s operating manual.
The SWR should be somewhere less than 1.5 to 1 on the frequencies
you wish to use.

Thursday, May 8, 2014

antenna theory

An antenna is a device for transmitting electromagnetic energy from the supply line to free space and vice versa. Antenna dares active element - the vibrator , an antenna may also contain passive components (one or more). To the active element of the antenna connected power line . When the alternating voltage supply line around the active element ( vibrator ) , a magnetic field. Passive antenna elements are needed for the formation of the magnetic field of a certain field of the structure and formation of the directional properties , impedance matching system " space - antenna power line .
The antennas can be categorized into three groups : linear antenna aperture antennas, surface-wave .
Linear antenna - is a regular cable or wiring system . Radiation is determined by the spread of linear antenna currents on its wires and their mutual orientation. This group includes the rhombic antenna vibrator . These antennas are often used in the square -wave range .
The next type of antennas is aperture antenna ( reflector antennas , parabolic ), these antennas are characterized by the presence of surface ( aperture ) , which is a transformation of energy propagating in the supply line to the radiation energy . Typically, the size of the aperture is significantly larger than the wavelength . Radiation of this antenna is determined by the structure of the electromagnetic field on the aperture .
And another group is a surface wave antenna . The emission of these antennas plays the role of a surface wave . It extends along the antenna part in the process of radiation. Antenna radiation is determined by the way of connecting to the power supply line and the condition of wave propagation along the antenna . Representative of this group is the antenna Uda - Yagi .
The antenna system is simply a collection of separate antennas. Application of the antenna system increases the possibility of the formation of the desired patterns . The antenna system provides a higher gain compared with a single antenna for enhancement (in level signal).