AmateurRadioTechnicianClassElement2Course…4658业余无线电技师班2元课程.pptx

1General Class Element 3 Course PresentationELEMENT 3 SUB-ELEMENTSG1 Commissions RulesG2 Operating ProceduresG3 Radio Wave PropagationG4 Amateur Radio Practices G5 Electrical PrinciplesG6 Circuit ComponentsG7 Practical CircuitsG8 Signals and EmissionsG9 AntennasG0 Electrical and RF Safety2Electrical and RF SafetyOne way that RF energy can affect human body tissue is that it heats body tissue.(G0A01)The following properties are important in estimating whether an RF signal exceeds the maximum permissible exposure(MPE)(G0A02)Its duty cycleIts frequencyIts power densityNever stand in front of a microwave feedhorn antennaOn transmit,it radiates a highly concentrated beam of RF energy All of these choices are correct.3Electrical and RF SafetyYou can determine that your station complies with FCC RF exposure regulations:(G0A03)By calculation based on FCC OET Bulletin 65By calculation based on computer modelingBy measurement of field strength using calibrated equipmentTime averaging in reference to RF radiation exposure means the total RF exposure averaged over a certain time.(G0A04)The general equation for time averaging exposure equivalence is:Sexp texp=Slimit tavgAll of these choices are correct.4Electrical and RF SafetyIf an evaluation of your station shows RF energy radiated from your station exceeds permissible limits you must take action to prevent human exposure to the excessive RF fields.(G0A05)(G0A06 Deleted by QPC)When evaluating RF exposure,a lower transmitter duty cycle permits greater short-term exposure levels.(G0A07)An amateur operator must perform a routine RF exposure evaluation to ensure compliance with RF safety regulations when transmitter power exceeds levels specified in part 97.13.(G0A08)Duty Cycle5Electrical and RF SafetyA calibrated field-strength meter with a calibrated antenna can be used to accurately measure an RF field.(G0A09)Jerrod Model 704BElectro-metrics em-7530Homebrew by KA7OEI of Utah Amateur Radio Club6Electrical and RF SafetyIf an evaluation shows that a neighbor might receive more than the allowable limit of RF exposure from the main lobe of a directional antenna,take precautions to ensure that the antenna cannot be pointed in their direction.(G0A10)If you install an indoor transmitting antenna,make sure that MPE limits are not exceeded in occupied areas.(G0A11)MPE=Maximum Permissible ExposureTurn off the transmitter and disconnect the feed line whenever you make adjustments or repairs to an antenna.(G0A12)7Electrical and RF SafetyWhen installing a ground-mounted antenna,it should be installed so no one can be exposed to RF radiation in excess of maximum permissible limits.(G0A13)Only the hot wires in a four-conductor line cord should be attached to fuses or circuit breakers in a device operated from a 240-VAC single-phase source.(G0B01)Notice wood safety fence.Keep a safe distance away from antenna during all transmissions.8Electrical and RF SafetyAccording to the code,AWG number 12 is the minimum wire size that may be safely used for a circuit that draws up to 20 amperes of continuous current.(G0B02)15 amperes is the size of fuse or circuit breaker that would be appropriate to use with a circuit that uses AWG number 14 wiring.(G0B03)9Electrical and RF SafetyDanger of carbon monoxide poisoning is a primary reason for not placing a gasoline-fueled generator inside an occupied area.(G0B04)Carbon Monoxide is serious stuff,dont take it lightly!10Electrical and RF SafetyCurrent flowing from one or more of the hot wires directly to ground will cause a Ground Fault Circuit Interrupter(GFCI)to disconnect the 120 or 240 Volt AC line power to a device.(G0B05)11RF&Electrical Safety12Electrical and RF SafetyThe metal enclosure of every item of station equipment must be grounded because it ensures that hazardous voltages cannot appear on the chassis.(G0B06)Enclosures,chassis,and all metal housings should be common grounded.13Electrical and RF SafetyOne of the practices that should be observed for safety when climbing on a tower using a safety belt or harness is to always attach the belt safety hook to the belt D-ring with the hook opening away from the tower.(G0B07)Always disconnect the feedline from the transmitter before going up a tower to work on antennaprevents accidental RF radiation exposure.Always think safety first when working on towers.14Electrical and RF SafetyAny person preparing to climb a tower that supports electrically powered devices should make sure all circuits that supply power to the tower are locked out and tagged.(G0B08)Soldered joints should not be used with the wires that connect the base of a tower to a system of ground rods because a soldered joint will likely be destroyed by the heat of a lightning strike.(G0B09)One danger from lead-tin solder is that lead can contaminate food if hands are not washed carefully after handling.(G0B10)15Electrical and RF SafetyGood engineering practice for lightning protection grounds includes bonding them together with all other grounds.(G0B11)Notice green cable as common ground under floor and connected to building column.Notice wide copper straps16Electrical and RF SafetyThe purpose of a transmitter power supply interlock is to ensure that dangerous voltages are removed if the cabinet is opened.(G0B12)When powering your house from an emergency generator,you must disconnect the incoming utility power feed.(G0B13)17Electrical and RF SafetyElectrical safety inside the ham shack is covered by the National Electrical Code.(G0B14)RF exposure limits to the human body are covered by ANSI,not by the NEC.18Electrical and RF SafetyFor an emergency generator installation,the generator should be located in a well ventilated area.(G0B15)Gasoline-powered generators may emit exhaust gases that could be hazardous.When being charged,a lead acid storage battery may give off explosive hydrogen gas.(G0B16)