Basic Radio: Understanding the Key Building Blocks

256 Pages·2006·32.67 MB·English

by  Joel R. Hallas

e key b i i
398780 1605
Joel Hallas, WIZR Michelle Bloom, WBlENT Sue Fagan
Jodi Morin, KAlJPA
David Pingree, NINAS
Copyright © 2005 by
The American Radio Relay League, Inc.
Copyright secured under the Pan-American
Convention
International Copyright secured
This work is Publication No.313 ofthe Radio
Amateur's Library, published bythe ARRL.
All rights reserved. No part ofthis work may
be reproduced inany form except bywritten
permission of the publisher. All rights of
translation are reserved.
Printed inthe USA
Quedan reservados todos los derechos
1st Edition
1st Printing
ISBN: 0-87259-955-8
Radio is all around us. We can't escape it. The radio spec
trum follows us wherever we go, whether we useit or not. But
wedouseit:We listen totheradioinourcar,useourcellphones
and counton the radio in Fido's collar to keep him in our yard.
Radio isoneofthemany applications ofelectronics. Others
that come to mind are computers, entertainment systems, other
telecommunications systems, control systems, security systems,
manufacturing systems, automotive systems, game players and
almost everything we touch or use in the twenty-first century.
But radio was one of the first developments of electronic prin
ciples, because of its importance to public safety.
This bookwill exploreradio-whatit does andhow it does
it. Basic Radio will take you beyond the elementary electronic
concepts presented in a book such as ARRL's Understanding
Basic Electronics or asimilarcourse of study inelectronicprin
ciples to amore completeunderstanding of how radio works its
magic.
David Sumner, KIZZ
Executive Vice President
Newington, Connecticut
September 2005
Chapter 1 Communicating Without Wires
Chapter 2 The Simplest Receiver-The Crystal Set
Chapter 3 Enhancing the Simplest Receiver
Chapter 4 Oscillators-the Beating Hearts of Modem Radios
Chapter 5 Frequency Synthesizers
Chapter 6 Mixing it Up With a Mixer
Chapter 7 Filtering Out What YouDon't Want
Chapter 8 Active and Digital Filtering
Chapter 9 Heterodyne Receivers-Putting the Pieces Together
Chapter 10 The Modem Superheterodyne
Chapter 11 Superheterodyne Receivers-Making them Sing
Chapter 12 Transmitters-the Other Side of the Equation
Chapter 13 Transmitting Voice
Chapter 14 Power Amplifiers, a Step Up
Chapter 15 Propagation-Getting YourSignal Where YouWant It
Chapter 16 Transmitting Antennas
Chapter 17 Receiving Signals, the Other Side of the Coin
Chapter 18 Using EZNEC to Model Real Antennas
Chapter 19 Line-of-Sight Communications Systems
Chapter 20 Communications Systems-Going the Extra Mile
Chapter 21 Ground-Wave And Ionospheric Communications
Chapter 22 Communications Regulation and Services
Chapter 23 Radiolocation Systems
Chapter 24 Radionavigation Systems
Chapter 25 Where is Technology TakingUs Next?
Appendix Radio Construction Projects
Glossary
Index
The national association for Am.ateur Radio
TheseedforAmateurRadiowasplanted inthe 1890s,whenGuglielmo Marconi beganhisexperiments
inwirelesstelegraphy.Soonhewasjoinedbydozens,thenhundreds,ofotherswhowereenthusiasticabout
sending andreceiving messages through the air-some with acommercialinterest, but others solely out
ofalove forthisnew communications medium. TheUnited States governmentbegan licensing Amateur
Radio operators in 1912.
By 1914, there were thousands of Amateur Radio operators-hams-in the United States. Hiram
Percy Maxim, aleadingHartford, Connecticutinventorand industrialist, saw the need for anorgani
zation to band together this fledgling group of radio experimenters. In May 1914 he founded the
American Radio Relay League (ARRL) to meet that need.
Today ARRL, with approximately 170,000members, is the largest organization of radio amateurs
in the United States. The ARRL is a not-for-profit organization that:
promotes interest in Amateur Radio communications and experimentation
1II
• represents US radio amateurs in legislative matters, and
..maintains fraternalism and ahigh standard of conduct among Amateur Radio operators.
At ARRL headquarters in the Hartford suburb of Newington, the staff helps serve the needs of
members. ARRL is also International Secretariatfor the International Amateur Radio Union, which
is made up of similar societies in 150 countries around the world.
ARRL publishes the monthlyjournal QST, as well as newsletters and many publications covering
all aspects ofAmateurRadio. Its headquarters station,WIAW, transmits bulletinsofinteresttoradio
amateurs and Morse code practice sessions. The ARRL also coordinates an extensivefield organiza
tion, which includesvolunteerswhoprovidetechnicalinformationandothersupportservicesforradio
amateurs as well as communications for public-service activities. In addition, ARRL represents US
amateurswiththeFederalCommunicationsCommissionandothergovernmentagenciesintheUSand
abroad.
MembershipinARRLmeansmuch more than receiving QSTeachmonth. Inadditiontothe services
alreadydescribed,ARRLoffers membershipservicesonapersonallevel,suchastheARRLVolunteer
Examiner Coordinator Program and a QSL bureau.
Full ARRL membership (available only to licensed radio amateurs) gives you a voice in how the
affairs of the organization are governed. ARRL policy is set by aBoardof Directors (one from each
of 15Divisions). Each year, one-third of the ARRLBoardof Directors stands for electionby thefull
members they represent. The day-to-day operation of ARRL HQ is managed by an Executive Vice
President and his staff.
Nomatterwhat aspectofAmateurRadio attractsyou, ARRL membershipisrelevantandimportant.
TherewouldbenoAmateurRadio asweknow ittoday were itnot for the ARRL. We wouldbehappy
towelcomeyou asamember! (AnAmateurRadio licenseisnot requiredfor AssociateMembership.)
For more informationaboutARRLand answers toanyquestionsyou may have aboutAmateurRadio,
write or call:
ARRL-The national association for Amateur Radio
225 Main Street
Newington CT 06111-1494
Voice: 860-594-0200
Fax: [phone]
E-mail: [email protected]
Internet: www.arrl.org/
Prospective new amateurs call (toll-free):
800-32-NEW HAM (800-326-3942)
You can also contact us via e-mail at [email protected]
or check out ARRLWeb at http://www.arrl.org/

YlJ
ommunica Without WireJ'
(Wef{
fm ·tlll)
Chuck Hutchinson, K8CH,works on the Vagiantennas on his tower.
Contents
Where Did Radio Come From? 1-2
What isThis Radio Thing All About? 1-5
So How Do the Signals GetThere? 1-7
Antennas-The Long and Short of It 1-9
Review Questions 1-10
Radio was onthe logical Fig 1-1. While semaphore communi
evolutionary path behind a number cation can be quite efficient, it suffers
of other systems designed to carry from some limitations. Itcan only be
information over distances. Before used in daylight, anyone within sight
there were electrical communica could read the mail and a signalman
tions systems, there were anumber standing up on ahigh spot sohis
of communications systems that flags could be seen atadistance was
were visually based. Anyone who aneasy target. Perhaps that's why
has ever watched an American that kind of signalman is hard to find
Western movie has likely seen these days! (A)
Native Americans communicating The mechanically driven sema
through the use of smoke signals, phore, a device with mechanical arms
only one of anumber of visual activated by levers from an office
communications systems. Parallel below, and situated on amountaintop
developments going back perhaps tower was the basis for acommunica
even longer included the use of tions network spanning much of
signal fires, as well as asophisti Europe during the Napoleonic era, a
cated system of drum-based long time before radio. These towers,
communications that could send positionedso each one could see the
messages across the African next, allowed amessage to be relayed
continent. from station to station. While the data
rate may have been slower than we're
Semaphore
used to, the messages traveled atthe
The insigniaofthe US Army speed oflight! A variant of such a
(8)
Signal Corps, with which your system, with electrically driven arms,
author once served, consists of two was used as arailroad signaling
crossed signal flags. These signal, system for many years and may still
or semaphore flags, could be used be in use in some areas.
to signal overrelatively large line
Electrical Communications
of-sight distances by the transmit
ting signalman holding the two the Telegraph
flags at particularangular positions The telegraph, perhaps the first in
around the body, each position along line of electrically operated
indicating aletter ofthe alphabetor communications systems had its
anumeral. The space around the genesis in the invention of the
body was divided into eight electromagnetin 1825.A number of
positions with the first seven letters people operated an electromagnet
corresponding to left-hand flag from aremote location to perform
down, with the right-hand flag rudimentary signaling, however,
(C)
progressing from part way up Samuel F.B. Morse is generally UBR1-0101
around the circle. The next seven credited with developing the first
with the left-hand flag part way up complete system. This struggling Fig t-t-s-Hand semaphore
on the right, etc. artist and NYU Art Professormade a positions for the letters A, Band C.
In an interestingbridge to later mid-life career change that changed
day technology, rather than having not only his life, but thelives of telegraph used a clever electrome
separate codes for numerals, the everyone who followed as well. chanical arrangement to cause a pen
code used the letters A through Ito His telegraph, first publicly to move across moving paper tape
mean the numerals 1through 9,if demonstrated in 1838, was a major when the sending key was closed.
precededby a special NUMERALS milestone and perhaps the first This is the origin of the terms mark
signal, in amanner similar to the system that could be called a tele and space, the gap between marks,
much later Baudotteletype code. communications system, although still in currentuse in data communi
The positions of the flags for the that term came into vogue many cations. Later versions used other
letters A, BandCare shown in years later. The original Morse marking mechanisms and eventually,
1-2 Chapter 1
based on their being sent on different competing companies at each end of
frequencies. Today we would call long-distance lines than of technol
this afrequency division multiplexer, ogy. The automatic (forerunner of
but atthat time itled Bell to the the dial) exchange was invented in
thought that instead of carrying 1889 by Almon B. Strowger, a
telegraph signals his apparatus might Kansas City undertaker, who was
be used to carry the different sounds upset after finding that the local
of human speech. human telephone exchange operator
Bell succeededin his experiments was steering business to a competi
and in 1875 was able to file for a tor.
Fig 1-2-Earlywire-line telegraph
key and sounder.This was well patentfor his invention, surprisingly
Next Step-Radio
used in USrailroad telegraph justhours ahead of anotherinventor.
service in the 1800s. (Thanks to Bell's early telephones were offered While the telegraph was being
Dan Henderson, NtND,for the loan as rental units, apractice that rolled out across the US frontier and
ofthis familyheirloom.)
continued until the US antitrust much ofthe rest ofthe world, a
especially in the US, operators settlementknown as the modified Scottish physicist and mathemati
learned to more efficiently decode by finaljudgmentof1984. Renters of cian' James Clerk Maxwell, was
ear, allowing a significant increase in his apparatus would independently formulating the mathematical basis
speed and thus throughput. contractto have wires installed of electromagnetic theory. In 1861 he
In 1844, a government-sponsored between the end points to provide a published his work predicting the
demonstration system was put in kind of intercom service. Within a waves that would travel from awire
place betweenWashington, DC, and few years after Bell invented his carrying a changing current, laying
Baltimore, Maryland. Following a telephone, switchboards were the groundworkfor what we call
successful demonstration to members devised to let auser communicate radio. Maxwell's equations allow the
of Congress the inventor and his with other users, and in 1878 the first prediction of allthe resulting fields
partners extendedthe line to Phila telephone exchange was established involved in the generations of such
delphia and New YorkCity and in New Haven, Connecticut. This waves.
offered commercial service. In 1851, made the telephone aviable facilita It remainedfor another scientist,
the telegraph began use as arailroad tor of commerce and communica the German HeinrichHertz in 1886,
dispatch system, a telegraph key and tions. Long-distance service started to actually demonstrate the existence
sounderfrom the late 1800s is shown quickly thereafter and for the next of radio waves. His experimentwas a
in Fig 1-2. Tenyears later the few decades, the history of the validation ofMaxwell's work, not an
Western Union Telegraph Company telephone was more a story of legal attemptto establish a new communi
built a transcontinental telegraph and regulatory battles between cations medium.
system effectively making the two
year old Pony Express
service obsolete
overnight. Interestingly,
the first transatlantic
telegraph cable was
installed some years
earlierbut burned out
after only 30 days due
to the fact that the users
didn't fully understand
the limitations of the
then-current technology.
The Telephone
the Next Step
Alexander Graham
Bell had been working
on aharmonic tele
graph, a system that
would allow multiple
telegraph channels to be
Fig 1-3-Marconishore radiotelegraph station at South Wellfleet, Cape Cod,
sent simultaneously over
Massachusetts in 1901.The towers were 200 feet tall and made of wood.They did not
a single pair of wires, survive Atlantic storms for long. (Photo courtesyofMarconi Corporation, Pt.c.)
Communicating Without Wires 1=3
Developmentofradio into a code then used by landline operators. the operators for each. Shipboard
commercial communications system, By that time, wire-line telegraph radio operators wore the uniform of
including a corporate structure that was well establishedfor communica the Marconi Company. Their
still bears his name, was left to tions on land, andby underseacable exploits at saving lives, often atrisk
Guglielmo Marconi, an Italian. across bodies of water.The missing of their own, made them heroes of
Although Nikola Telsais actually link was communication with ships the day.
credited with the invention of radio, at sea, which were atthe mercy of Since the time of Marconi's radio
Marconi clearly developed radio into the elements without any way to call operators, radio has grown in all
a significantbusiness enterprise. He for help. Marconi sought tofill that dimensions and has become a major
is said tohave sent his first signals in need through the provisioning of part of our lives incountless ways.
1895, communicated across the what today would be called a turnkey Wewill explore these developments
English Channel in 1899and across service. His company supplied the from both a technological and
the Atlantic three years later. His shore stations (see Fig 1-3), the historical perspective as we progress
system used avariant ofthe Morse shipboard stations (see Fig 1-4), and through these chapters.
Fig 1-4-Marconi shipboard radiotelegraph station from 1900. (Photo courtesy of Marconi Corporation, PLC.)
1-4 Chapter 1