FORMhSWRTHYPHASCISPELPRGHDOC h PICP69LINP6Z BOXP6Z dOVLP6Z dSWCL@BlackWhiteRedGreenBlueCyanYellowMagentafSalmonwPeachUBrownellowLight GreenwwwGrey DarkOrangeݙVanillalowGrey LightIDXHIDXDSoftSansdTitleepz,IDXDSoftSansdBlank LinefIDXDSoftSansdLetter HeadergIDXDSoftSans dIndex EntryhTOCH TOCDSoftSansdTitlenz%TOCDSoftSans dBlank LineoTOCDSoftSansdZLevel 1pTOCDSoftSans dZLevel 2qTOCDSoftSerif dLevel 3rTOCDSoftSerif dhLevel 4sTOCDSoftSerif dvLevel 5tTOCDSoftSerif d*Level 6uTOCDSoftSerif dLevel 7vTOCDSoftSerif d8Level 8wIDXPSEC1 PTPAG3pA PRN3KBVtils:APPLICATIONS/FinalWriter/FWFonts/SWOLFonts/Serif/WŬWW~WW { dELX.FormulaText{WPASDSoftSansdDocument TitlePASDSoftSansdSection Namepz??PASDSoftSansdTopic Nameq{??PASDSoftSansdSub Topic 1r|??PASDSoftSansdSub Topic 2s}??PASDSoftSans dBodyPASDSoftSans dIndented BodyTOCP!rOUTPBIBPTOIPENDPDSP2PHHFDASoftSans dSoftSans dPNDASoftSans dSHPP6Z dGRMRStrictly.For Business Writing.For Casual Writing.Custom 1.Custom 2.Custom 3.IDXLConductorsTDINFFCOP3`W9fW/pPFDTASoftSans_Bold{WŬWΆWvtUtils:APPLICATIONS/FinalWriter/FWFonts/SWOLFonts/hW62W6W6JoW6:W6W6RW6oW6jW6W6W6 oW6 W6 &W7cW7;DoW7;W7<\W6W6roW6W7DW7W7\oW7W7tW7W7oW7W7W70W7CELLRULEATTR dCHRSRadio frequencyCLLECELLRULE ATTR dCHRS FrequencyCLLECELLRULE ATTR dCHRS WavelengthCLLECELLRULE ATTR dCHRS Band WidthCLLECELLRULEATTR dCHRS VLF - Very Low frequencyCLLECELLRULE,ATTR dCHRS ATTR dCHRS 10kHz - 30kHzCLLECELLRULE ATTR dCHRS 30km - 10kmCLLECELLRULEATTR dCHRS 20 KHzCLLECELLRULEATTR dCHRS LF - Low FrequencyCLLECELLRULE,ATTR dCHRS ATTR dCHRS30kHz - 300kHzCLLECELLRULE ATTR dCHRS 10km - 1kmCLLECELLRULEATTR dCHRS 270 KHzCLLECELLRULEATTR dCHRS MF - Medium FrequencyCLLECELLRULEATTR dCHRS 300kHz - 3000kHzCLLECELLRULE ,ATTR dCHRS ATTR dCHRS 1km - 100mCLLECELLRULE ATTR dCHRS 2700 KHzCLLECELLRULEATTR dCHRS HF - High FrequencyCLLECELLRULE ,ATTR dCHRS ATTR dCHRS 3MHz - 30MHzCLLECELLRULE ,ATTR dCHRS ATTR dCHRS 100m - 10mCLLECELLRULEATTR dCHRS 27 MHzCLLECELLRULEATTR dCHRSVHF - Very High FrequencyCLLECELLRULE,ATTR dCHRS ATTR dCHRS30MHz - 300MHzCLLECELLRULE ,ATTR dCHRS ATTR dCHRS10m - 1mCLLECELLRULEATTR dCHRS270 MHzCLLECELLRULEATTR dCHRSUHF - Ultra High FrequencyCLLECELLRULE,ATTR dCHRS ATTR dCHRS300MHz - 3000MHzCLLECELLRULE ,ATTR dCHRS ATTR dCHRS 1m - 10cmCLLECELLRULE ATTR dCHRS 2700 MHzCLLECELLRULEATTR dCHRSSHF - Super High FrequencyCLLECELLRULE ,ATTR dCHRS ATTR dCHRS 3GHz - 30GHzCLLECELLRULE ,ATTR dCHRS ATTR dCHRS 10cm - 1cmCLLECELLRULE,ATTR dCHRS ATTR dCHRS27 GHzCLLECELLRULEATTR dCHRSEHF - Extremely High Freqncy.CLLECELLRULE,ATTR dCHRS ATTR dCHRS30GHz - 300GHzCLLECELLRULE ,ATTR dCHRS ATTR dCHRS 1cm - 1mmCLLECELLRULE ,ATTR dCHRS ATTR dCHRS 270 GHzCLLECELLRULEATTR dCHRSCLLECELLRULEATTR dCHRSCLLECELLRULEATTR dCHRSCLLECELLRULEATTR dCHRSCLLEGINFUtils:GRAPHICS/PPaint/Brushes/FWriter5/Line2.bshMXRMXRM=@n9BlackFORMTILBMBMHD& D,CMAP0f"@@CAMGBODY<U߻TU߻TU߻Twww<GINF SHD1PW69W66W62^PTMainTBDYRULEHATTR dCHRSElectronic Servicing yr.1 pt.1ATTR dCHRS ATTR hdCHRS ATTR hdCHRS ATTR dCHRSLecture: 018.TATTR xdCHRS ATTR hdCHRS ATTR hdCHRS ATTR hdCHRSThu - 16 - Jan ATTR hdCHRS- 1997RULEATTR dCHRSRULEATTR xCHRSCommunication principlesRULEATTR dCHRSRULEATTR dCHRSRULE  ATTR dCHRS ObjectivesRULEEATTRE dCHRSE1: Understands the basic requirements for intelligent communication.RULE[ATTR[ dCHRS[2: States the nature of sound waves and the relationship between wavelength and frequency.RULEbATTRb dCHRSb3: Considers use of sound waves, ultrasonic waves and coded electrical signals in communications.RULEHATTRH dCHRSH4: States advantages in using electromagnetic waves for communications.RULEZATTRZ dCHRSZ5: Determines the relationship between frequency and wavelength of electromagnetic waves.RULE/ATTR/ dCHRS/6: States applications for data communicationsRULEATTR dCHRSRULE ATTRdCHRSCommunication by SoundRULEATTR dCHRSIntelligent communication is only possible by two partners that know the same code or language. Sound is the main communication in nature and the first in mankind. RULEATTR dCHRSRULEATTR dCHRSSound is vibrations in air (or other media). In fact sound do not travel in a vacuum, so it can only travel through a solid, liquid or gaseous medium. The denser the medium, the faster the sound travels. Eg:RULEUATTRU dCHRSUAIR=340m/s (Mach 1), WATER=1400m/s, WOOD=3000-4000m/s, BRASS=3500m/s, IRON=5130m/sRULEATTR dCHRSRULE.XATTRhdCHRS ATTRhdCHRS ATTRhdCHRS ATTR+dCHRS+Speed of sound = Frequency x Wavelength RULEDATTR dCHRS ATTR  dCHRS ATTR hdCHRS ATTR hdCHRS ATTR hdCHRS ATTR hdCHRS ATTR; dCHRS;m/s) (Hertz) (metres) RULEATTR dCHRSRULEnATTR dCHRSThe human ear can hear a maximum from 20Hz to 20kHz and this is known the audio frequency range (a/f range). Frequencies which are below 20Hz are known as ATTR dCHRS InfraSonicATTR, dCHRS,, and frequencies above 20kHz are known as ATTR dCHRS UltraSonicATTR dCHRS RULEATTR dCHRSRULE3nATTR dCHRSIn a sound wave, the amplitude determines the loudness, whereas the frequency determines the pitch. The overall waveshape determines the quality on timbre of sound (if the sound is piano, trumpet, violin etc.). High pitched / freq notes are known as ATTR dCHRSTrebleATTR. dCHRS., while low pitched / freq notes are known as ATTR dCHRSBassATTR dCHRS.RULECATTRC dCHRSCThe audio range of speech and telephone is between 300Hz - 3400Hz. RULEATTR dCHRSRULEYATTRY dCHRSYA sound wave is air pressure variation against time. If the pressure variation is an increase, the part of wave is compressed (compression), and if the pressure variation is a decrease, the part of wave is decompressed (decompression or rarefaction). Compressions ore the +ve part of the wave, while Decompressions are the -ve part of the wave.RULEATTR dCHRSRULE (ATTR(dCHRS(Communications by ElectroMagnetic waves.RULEATTR dCHRSSound waves do not travel through a vacuum and the distance they cover is very small. To communicate over long distance, sound is first changed into electricity then sent over wires which carry the signal. This is done in telephony and cable radio. To communicate over distances where wires are not possible. A wire less equipment is used. Here the wires are replaced by radio waves. Radio waves, light waves, heat waves are electro magnetic waves. (see book pg.19 fig. 2.9)RULEATTR dCHRSRULE6ATTR$ dCHRS$ElectroMagnetic Waves travel at 3x10ATTR dCHRS8ATTR dCHRS m/s = 300,000,000 m/s. There is nothing faster from speed of Electro magnetic wave, which unlike sound waves ElectroMagnetic waves travel through a vacuum, but do not travel through liquid or solid. ATTR; dCHRS;For example the loss of radio reception when vehicle is undATTR dCHRSer a tATTR dCHRSunnelATTR dCHRS. RULE:nATTR& dCHRS&Electro Magnetic Field has two fields ATTR dCHRS ATTR dCHRS 1 - ATTR dCHRSelectATTR dCHRS ric fieldRULEATTR hdCHRS ATTR hdCHRS ATTR hdCHRS ATTR hdCHRS ATTR hdCHRS ATTR hdCHRS ATTR hdCHRS2 - ATTR hdCHRSmagnetATTR hdCHRSic fieldRULEATTR hdCHRSRULEBATTR hdCHRSElectric fieldATTR) hdCHRS) depends on its Voltage for its strength.ATTRi hdCHRSi Voltage is proportional to electric field. A capacitor stores electricity in the form of electric field.RULE^,ATTR2 hdCHRS2Magnetic field depend on current for its strength.ATTR, hdCHRS, Current is proportional to magnetic field. RULEATTR hdCHRSRULEATTR hdCHRSRULE ATTRhdCHRSClassification of radio waves:RULEATTR hdCHRSRULEATTR hdCHRSRULEATTR dCHRS RULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRULE ATTRdCHRSFrequency and Band Width.RULEMATTRM dCHRSMBand Width is a range of adjacent frequencies. It is also measured in Hertz. RULECATTRC dCHRSCBand Width = Upper frequency - Lower frequency. See examples above.RULEATTR dCHRSRULEATTR dCHRSVLF is not used for TV and sound, but used in radio beacons. A beacon is a radio signalling station which serves as an aid for navigation (ship / airplane). VLF to HF use amplitude modulation AM. Modulation means to print information on the radio carrier. The radio wave is the carrier of the information and they replace the old wires. We can compare it with the letter sheet of paper. There are 3 types of modulation which can be used:RULEATTR dCHRSRULEATTR dCHRS1) Amplitude Modulation (AM)RULEATTR dCHRS2) Frequency Modulation (FM)RULE8ATTR8 dCHRS83) Pulse Modulation (used for remote control systems) RULE ATTRdCHRSRULE ATTRdCHRSNotes:RULEMATTRM dCHRSM - The size of aerial is inversely proportional to the transmitted frequency.RULEFATTRF dCHRSF - Aerial size for transmitting is equal to aerial size for receiving.RULEATTR dCHRSRULEATTR dCHRSRULEATTR dCHRSRMSTRULEATTR dCHRSLMSTRULEATTR dCHRS