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NCATT Radio Communication Systems EndorsementStudy online at https://quizlet.com/_8kgaeb1.Very Low Frequen-cy (VLF)3 KHZ - 30 KHz2.Low Frequency (LF)30 KHZ - 300 KHz3.Medium Frequency (MF)300 KHZ - 3 MHz4.High Frequency (HF)3-30 MHz5.Very High Frequen-cy (VHF)30-300 MHz6.Ultra High Frequen-cy (UHF)300 MHz - 3 GHz7.Super High Fre-quency (SHF)3-30 GHz8.Extremely High Fre-quency (EHF)30 GHz - 300 GHz9.FrequencyThe number of electronic .eld oscillations that take place in one second (in the case of radio transmissions)10.Carrier WaveThe high frequency alternating current that can be modulated to carry intelli-gence by propagation as a radio wave11.ModulationThe process of changing an electromagnetic wave's ability to transmit infor-mation by varying it's amplitude, phase, or frequency.12.AM (amplitude modulation)The amplitude of the carrier wave varies with the change in amplitude and frequency of the information signal1 / 16
NCATT Radio Communication Systems EndorsementStudy online at https://quizlet.com/_8kgaeb13.FM (frequency modulation)The carrier amplitude stays constant while the carrier frequency is changed by the modulating or information signal14.Ground WavesBelow HF band (3MHz). They follow the curvature of the earth.15.Sky WavesOperate in HF Band (3-30MHz). They travel in straight lines. They bounce or refract o8 the ionosphere, which is made up of layers of ionized particles from about 60-200 miles high. This characteristic can be used to achieve long-range transmission or radio signals.16.Space WavesWaves transmitted at frequencies above the HF Band. Travel in straight lines. Do not bounce o8 ionosphere. Used to communicate with satellites, signals are above 30 MHz.17.Transmitter2 / 16
NCATT Radio Communication Systems EndorsementStudy online at https://quizlet.com/_8kgaebElectronic unit that accepts information and converts it into a radio frequency signal capable of being transmitted over long distances18.Functions of a Transmitter1.) it must generate a signal of the correct frequency at a desired point in the EM spectrum2.) it must provide some form of modulation that causes the information signal to modify the carrier signal3.) it must provide su=cient power ampli.cation to ensure that the signal level is high enough so that it will carry over the desired distance19.OscillatorGenerates the carrier signal at the desired frequency20.Common Oscilla-tors used in Avion-ics1.) VFO - Variable Frequency Oscillator 2.) Crystal Oscillator 3.) PLL - Phase Locked Loop Oscillator21.Simple OscillatorLC circuit made up of a capacitor and inductor connected in parallel. The LC circuit has a resonant frequency that matches the desired frequency. Must have energy fed back into circuit to maintain oscillations22.ueM2lrzcComponent that increases the strength of a signal and is found in both transmitters and receivers. Increases signal strength sent to antenna so that EM waves will travel a useful distance. Receivers use ampli.ers to ensure signal can be heard.23.Basic Types of Am-M2lrzcqyaqznylhyTransmitters1.) Linear2.) Class C 3.) Switching Ampli.ers24._lhzocyueM2lrzcqClassi.ed as A, AB, or B, provide an output directly proportional to their input but at a higher power level. All audio ampli.ers are linear.25.Use of Linear Am-M2lrzcq3 / 16
NCATT Radio Communication Systems EndorsementStudy online at https://quizlet.com/_8kgaebClass A and B ampli.ers are used to increase the power level of changing amplitude radio frequencies such as AM radio signals. FM signals use more stable non-linear ampli.ers such as Class C or switching ampli.ers.26.ModulatorPortion of a transmitter circuit that modulates carrier wave. Superimposes audio frequency signal onto the carrier wave signal before it is sent to the antenna.27.DemodulatorRemoves RF component of the modulated RF signal and produces an audio frequency output.28.Average Modula-tion Rate90-95% modulation. Over 100% can cause distortion. Modulation rate is ratio of AF (audio frequency-intelligence) to the RF (radio frequency-carrier)29.FilterRemoves unwanted frequencies. Usually made up of an arrangement or in-ductors and capacitors.30.Low-Pass FilterRemoves all frequencies above a certain value and passes the low frequencies.31.High-Pass FilterRemoves all frequencies below a certain value and passes the high frequen-cies.32.Band-Pass FilterPasses energy in a particular range of frequencies between Fl and Fu.33.Band-Reject Filterholds back a band of frequencies-allows both higher and lower frequencies through34.AntennaAn electrical conductor that radiates or receives radio waves. May be Rx, Tx or both. Installation by airframe technician.35.Hertz Dipole Anten-naHalf-wave antenna. Because the overall length is equal to one half of the wavelength of the EM wave it is designed to send out or pick up. It is divided into two quarter-length sections with the transmission line connected at the center.4 / 16
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