WIXLIB

Group T3B – Radio WavesGroup T3A – Radio SignalsElectromagnetic Waves The two components of a radio wave are the electric andmagnetic fields The orientation of the electric field of a radio wave is usedto describe its polarizationPropagation Electromagnetic waves carry radio signals betweentransmitting and receiving stations Inside buildings, UHF signals are often more effectivethan VHF signals because the shorter wavelength of UHFsignals allows them to more easily penetrate thestructure of buildings When using a directional antenna, and if buildings orobstructions are blocking the direct line of sight path,your station may be able to access a distant repeater ifyou try to find a path that reflects signals to the repeaterSpeed of Light (and Radio Waves) A radio wave travels through free space at the speed oflight The approximate velocity of a radio wave as it travelsthrough free space is 300,000,000 meters per secondRadio Frequency Spectrum Designations The frequency range of the high frequency spectrum (HF)is 3 to 30 MHz (Wavelength is 100 m to 10 m) The frequency range of the very high frequency spectrum(VHF) is 30 to 300 MHz (Wavelength is 10 m to 1 m) The frequency range of the ultra-high frequency spectrum(UHF) is 300 to 3000 MHz (Wavelength is 1 m to 10 cm)Wavelength Wavelength is the distance a radio wave travels duringone complete cycle The formula for converting frequency to approximatewavelength is wavelength in meters equals 300 dividedby frequency in megahertz, that is, 300 fMHzwhere λ (lambda) is wavelength in meters andfMHz is frequency in megahertz. The wavelength gets shorter as the frequency increases The approximate wavelength of radio waves is often usedto identify the different frequency bands8Multi-Path Distortion If another operator reports that your station’s 2 metersignals were strong just a moment ago, but now they areweak or distorted, the you should try moving a few feet orchanging the direction of your antenna if possible, asreflections may be causing multi-path distortion The term picket fencing is commonly used to describe therapid fluttering sound sometimes heard from mobilestations that are moving while transmitting The part of the atmosphere that enables the propagationof radio signals around the world is the ionosphere A likely cause of irregular fading of signals that are beingreceived by ionospheric reflection is the randomcombining of signals arriving via different paths If data signals propagate over multiple paths, error ratesare likely to increaseAntenna Polarization If the antennas at opposite ends of a VHF or UHF line ofsight radio link are not using the same polarization, thatis, both either horizontal or vertical, the signals could besignificantly weaker Horizontal antenna polarization is normally used for longdistance weak-signal CW and SSB contacts using the VHFand UHF bands Because skip signals refracted from the ionosphere areelliptically polarized, either vertically or horizontallypolarized antennas may be used for transmission orreceptionBy-the-Group Technician Class Amateur Radio License Study Guide

Group T3C –Propagation and EnvironmentGroup T9A – AntennasDirect Mode (Line-of-Sight) The radio horizon is the distance over which two stationscan communicate by direct path VHF and UHF radio signals usually travel somewhatfarther than the visual line of sight distance between twostations because the earth seems less curved to radiowaves than to light The reason that direct UHF signals are rarely heard fromstations outside your local coverage area is because UHFsignals are usually not reflected by the ionospherePolarization A simple dipole mounted so the conductor is parallel tothe Earth's surface is a horizontally polarized antenna For vertical antennas, the electric field is perpendicularto the EarthIonospheric Modes The ten and six meters bands may provide long distancecommunications during the peak of the sunspot cycle The best time generally for long-distance 10 meter bandpropagation via the F layer is from dawn to shortly aftersunset during periods of high sunspot activity A 6 meter 1/2-wavelength wire dipole antenna has anapproximate length of 112 inches0.95 2 0.95 6 2 39.37 in 112 in To make a dipole antenna resonant on a higherfrequency, you would shorten it “Loading” an antenna refers to inserting an inductor inthe radiating portion of the antenna to make it electricallylongerMeteor Scattering The 6 meters band is best suited for communicating viameteor scatterAuroral Backscatter A characteristic of VHF signals received via auroralreflection is that the signals exhibit rapid fluctuations ofstrength and often sound distortedSporadic E Propagation Often when VHF signals are being received from longdistances, it is because the signals are being refractedfrom a sporadic E layer Sporadic E is most common cause of occasional strongover-the-horizon signals on the 10, 6, and 2 meter bandsTropospheric Ducting Tropospheric ducting is caused by temperatureinversions in the atmosphere Tropospheric scatter is responsible for allowing over-thehorizon VHF and UHF communications to ranges of about300 miles on a regular basisKnife-Edge Diffraction Knife-edge diffraction might cause radio signals to beheard despite obstructions between the transmitting andreceiving stations For a 3-meeting course, this point ends meeting 1.By-the-Group Technician Class Amateur Radio License Study GuideElectrical Length A quarter-wavelength vertical antenna for 146 MHz hasan approximate length of 19 inches0.95 4 0.95 300 146 4 39.37 in 19 inRubber Duck Antennas A disadvantage of the “rubber duck” antenna suppliedwith most handheld radio transceivers is that it does nottransmit or receive as effectively as a full-sized antenna A good reason not to use a “rubber duck” antenna insideyour car is that signals can be significantly weaker thanwhen it is outside of the vehicleRadiation Pattern The direction in which the radiation is strongest from ahalf-wave dipole antenna in free space is broadside tothe antenna The gain of an antenna is the increase in signal strengthin a specified direction when compared to a referenceantenna A beam antenna is an antenna that concentrates signalsin one direction The quad, Yagi, and dish antennas are directionalantennas A reason to use a properly mounted 5/8 wavelengthantenna for VHF or UHF mobile service is that it offers alower angle of radiation and more gain than a 1/4wavelength antenna and usually provides improvedcoverage VHF or UHF mobile antennas are often mounted in thecenter of the vehicle roof because a roof mountedantenna normally provides the most uniform radiationpattern9

Group T9B – Coaxial CableGroup T7C – Antenna Systems MeasurementsCoaxial cables The reason that coaxial cable is used more often than anyother feed line for amateur radio antenna systems is thatit is easy to use and requires few special installationconsiderations As the frequency of a signal passing through coaxial cableis increased, the loss increases Air-insulated hard line has the lowest loss at VHF and UHFfrequencies In typical amateur radio installations, the impedance ofthe most commonly used coaxial cable is 50 ohms The electrical difference between the smaller RG-58 andlarger RG-8 coaxial cables is that the RG-8 cable has lessloss at a given frequencyCoaxial cable A common use of coaxial cable is carrying RF signalsbetween a radio and antenna The power lost in a feed line is converted into heat The most common cause for failure of coaxial cables ismoisture contamination The outer jacket of coaxial cable should be resistant toultraviolet light because ultraviolet light can damage thejacket and allow water to enter the cable When compared to foam or solid dielectric types, adisadvantage of air core coaxial cable is that it requiresspecial techniques to prevent water absorptionConnectors PL-259 type coax connectors are commonly used at HFfrequencies A Type N connector is the more suitable connector forfrequencies above 400 MHz Coax connectors that are exposed to the weather shouldbe sealed against water intrusion to prevent an increasein feed line lossMaintaining Low SWR (Standing Wave Ratio) In an antenna system that uses coaxial cable feed line, Itis important to have a low SWR in order to allow theefficient transfer of power and reduce losses An antenna tuner matches the antenna systemimpedance to the transceiver's output impedance Erratic changes in SWR readings could be caused by aloose connection in an antenna or a feed line10Antenna Analyzer An antenna analyzer can be used to determine if anantenna is resonant at the desired operating frequencyStanding Wave Ratio The standing wave ratio (SWR) is a measure of how wella load is matched to a transmission line A reading of 1 to 1 on an SWR meter indicates a perfectimpedance match between the antenna and the feed line An approximate SWR value of 2 to 1 and above causesthe protection circuits in most solid-state transmitters tobegin to reduce transmitter power An SWR reading of 4:1 indicates an impedance mismatch Instead of an SWR meter you could use a directionalwattmeter to determine if a feed line and antenna areproperly matchedDummy Load The primary purpose of a dummy load is to prevent theradiation of signals when making tests A dummy load consist of a non-inductive resistor and aheat sinkBy-the-Group Technician Class Amateur Radio License Study Guide

Group T8A – Radio Wave ModulationGroup T8D – Digital CommunicationsContinuous Wave (CW) CW has the narrowest bandwidth The approximate maximum bandwidth required totransmit a CW signal is 150 HzCW CW is sent using International Morse code All of the following can be used to transmit CW in theamateur bandso Straight Keyo Electronic Keyero Computer KeyboardSingle Sideband (SSB) Single sideband is a form of amplitude modulation The approximate bandwidth of a single sideband voicesignal is 3 kHz As a voice mode, SSB is most often used for long-distance(weak signal) contacts on the VHF and UHF bands For voice transmissions, the primary advantage of singlesideband over FM is that SSB signals have narrowerbandwidth Upper sideband is normally used for 10 meter HF, VHF,and UHF single-sideband communicationsFrequency Modulation (FM) The approximate bandwidth of a VHF repeater FM phonesignal is between 10 and 15 kHz FM is most commonly used for VHF and UHF voicerepeaters FM is most commonly used for VHF packet radiotransmissionsTelevision (TV)The typical bandwidth of analog fast-scan TVtransmissions on the 70 cm band is about 6 MHzDigital Digital communications methods include all of thefollowing exampleso Packeto PSK31o MFSK All the following may be included in packet transmissionso A check sum which permits error detectiono A header which contains the call sign of the station towhich the information is being sento Automatic repeat request in case of error PSK means Phase Shift Keying PSK31 is a low-rate data transmission mode An ARQ transmission system is a digital scheme wherebythe receiving station detects errors and sends a requestto the sending station to retransmit the informationAutomatic Packet Reporting System (APRS) “APRS” means Automatic Packet Reporting System An example of an application of APRS (Automatic PacketReporting System) is providing real time tactical digitalcommunications in conjunction with a map showing thelocations of stations A Global Positioning System receiver provides data to thetransmitter when sending automatic position reportsfrom a mobile amateur radio stationTV The term NTSC refers to an analog fast scan color TVsignalBy-the-Group Technician Class Amateur Radio License Study Guide11

Group T0A – Electrical SafetyGroup T0B – Antenna and Tower SafetyElectrical Shock Current flowing through the body causes all of thefollowing health hazardso By heating tissueo It disrupts the electrical functions of cellso It causes involuntary muscle contractions All of the following are good ways to guard againstelectrical shock at your stationo Use three-wire cords and plugs for all AC poweredequipmento Connect all AC powered station equipment to acommon safety groundo Use a circuit protected by a ground-fault interrupter The green wire in a three-wire electrical AC plug isconnected to the safety ground A hazard that might exist in a power supply when it isturned off and disconnected is that you might receive anelectric shock from the charged stored in large capacitorsAntenna Location Establish a minimum safe distance from a power linewhen installing an antenna so that if the antenna fallsunexpectedly, no part of it can come closer than 10 feetto the power wires Avoid attaching an antenna to a utility pole because theantenna could contact high-voltage power wiresFire Safety The purpose of a fuse in an electrical circuit is to interruptpower in case of overload It is unwise to install a 20-ampere fuse in the place of a5-ampere fuse because excessive current could cause afire Home-built equipment that is powered from 120V ACpower circuits should always include a fuse or circuitbreaker in series with the AC hot conductorBattery safety A hazard that is presented by a conventional 12-voltstorage battery is that explosive gas can collect if notproperly vented If a lead-acid storage battery is charged or discharged tooquickly the battery could overheat and give off flammablegas or explode A safety hazard of a 12-volt storage battery is thatshorting the terminals can cause burns, fire, or anexplosionWork Crew Safety An important safety precaution to observe when puttingup an antenna tower is to look for and stay clear of anyoverhead electrical wires A crank-up tower must never be climbed unless it is in thefully retracted position It is never safe to climb a tower without a helper orobserver Before climbing an antenna tower, put on a climbingharness and safety glasses Members of a tower work team should wear hard hatsand safety glasses at all times when any work is beingdone on the tower The purpose of a gin pole is to lift tower sections orantennasTower Grounding Local electrical codes establish grounding requirementsfor an amateur radio tower or antenna Proper grounding for a tower includes having separateeight-foot long ground rods for each tower leg, bonded tothe tower and each other When installing ground wires on a tower for lightningprotection, ensure that connections are short and direct Sharp bends must be avoided for the groundingconductors used for lightning protectionLightning Protection A precaution that should be taken when installing devicesfor lightning protection in a coaxial cable feed line is toground all of the protectors to a common plate which isin turn connected to an external ground 12For a 4-meeting course, this point ends meeting 2.For a 2-meeting course, this point ends meeting 1.By-the-Group Technician Class Amateur Radio License Study Guide

Group T0C – RF SafetyGroup T4A – Station SetupHealth Risk RF radiation differs from ionizing radiation because RFradiation does not have sufficient energy to causegenetic damage VHF and UHF radio signals are non-ionizing radiation The exposure limits vary with frequency because thehuman body absorbs more RF energy at somefrequencies than at others If a person accidentally touches your antenna while youare transmitting, they might receive a painful RF burnGrounding and Power A flat strap is the best conductor to use for RF grounding For communications equipment, use a regulated powersupply because it prevents voltage fluctuations fromreaching sensitive circuitsEvaluating Risk 50 watts PEP at the antenna is the maximum power levelthat an amateur radio station may use at VHFfrequencies before an RF exposure evaluation is required All of the following are acceptable methods to determinethat your station complies with FCC RF exposureregulationso By calculation based on FCC OET Bulletin 65o By calculation based on computer modelingo By measurement of field strength using calibratedequipment All of the following factors affect the RF exposure ofpeople near an amateur station antenna:o Frequency and power level of the RF fieldo Distance from the antenna to a persono Radiation pattern of the antenna 50 MHz has the lowest value for Maximum PermissibleExposure limit Duty cycle is one of the factors used to determine safe RFradiation exposure levels because it affects the averageexposure of people to radiation In calculating the average time of RF exposure, the dutycycle is the percentage of time that a transmitter istransmittingManaging Risk You can make sure your station stays in compliance withRF safety regulations by re-evaluating the stationwhenever an item of equipment is changed One way amateur operators can prevent exposure to RFradiation that exceed FCC-supplied limits is to relocateantennas If the averaging time for exposure is 6 minutes, 2 timesas much power density is permitted if the signal ispresent for 3 minutes and absent for 3 minutes ratherthan being present for the entire 6 minutesBy-the-Group Technician Class Amateur Radio License Study GuideMicrophones Microphone connectors on amateur transceivers differfrom each other because some connectors include pushto-talk and voltages for powering the microphone To cure distorted audio caused by RF current flowing onthe shield of a microphone cable, install a ferrite chokeon the cableComputers The ways that a computer could be used in an amateurradio station include all of the following:o For logging contacts and contact informationo For sending and/or receiving CWo For generating and decoding digital signals When using a computer in digital communications, thecomputer’s sound card provides audio to the microphoneinput and converts received audio to digital form In packet radio stations, a terminal node controller (TNC)connects the computer to the transceiverBetween Transmitter and Antenna To monitor the standing wave ratio of the station antennasystem, an in-line SWR meter should be installed in serieswith the feed line, between the transmitter and antenna A filter installed between the transmitter and the antennacan reduce any harmonic emission from your stationMobile Installations The negative return connector of a mobile transceiver'spower cable should be connected at the battery or engineblock ground strap If a mobile transceiver’s received audio has a highpitched whine that varies with engine speed, then thesource is the alternator if another operator reports a variable high-pitched whineon the audio from your mobile transmitter, then prob

So you want to get your Amateur Radio License. Good! This study guide is intended to help you prepare for the Technician Class license exam. This study guide is without detailed explanation. Your class instructors, other study guides, and on-line websites can provide explanation of and insight to the ma