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Technician License Course Chapter 5 Amateur Radio Equipment

Technician License Course Chapter 5 Amateur Radio Equipment. Lesson Plan Module 12: Power Supplies and Batteries & RF Interference (RFI). Power Supplies. Most modern radio equipment runs from 12 volts DC. Household current is 120 volts AC.

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Technician License Course Chapter 5 Amateur Radio Equipment

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  1. Technician License CourseChapter 5Amateur Radio Equipment Lesson Plan Module 12: Power Supplies and Batteries & RF Interference (RFI)

  2. Power Supplies • Most modern radio equipment runs from 12 volts DC. • Household current is 120 volts AC. • Power supplies convert 120 volts AC to 12 volts DC. • 13.8 volts DC is the common voltage you will see. • This is the charging voltage for motorized vehicles.

  3. Types of Power Supplies Linear: Switching: Electronics instead of transformers Light weight and small Not as robust Less expensive • Transformers • Heavy (physically) • Heavy duty current • Expensive

  4. Power Supply RatingsVoltage and Current • Continuous duty – how much current can be supplied over the long term. • Intermittent duty – how much surge current can be supplied over the short term. • Regulation – how well the power supply can handle rapid current changes, and keep the voltage constant.

  5. Mobile Power Wiring Safety • Special requirements for safe car wiring: • Fuse both positive and negative leads. • Connect radio’s negative lead to where the battery ground connection is made. • Use grommets or protective sleeves to prevent wire chafing. • Don’t assume all metal in the car is grounded; modern cars are as much plastic as metal. • Car batteries hold lots of energy – shorting a battery could cause a fire.

  6. Mobile Power Wiring • Use wiring of sufficient gauge. • Too small wire can lead to excessive voltage drop. • Mobile Noise • Alternator whine – high pitched noise that varies with engine speed. • Ignition noise – raspy or popping noise that also varies with engine speed. • There are filters that can help.

  7. Batteries • Create current through a chemical reaction. • Made up of individual cells (approximately 1.5 volts per cell) connected in series or parallel. • Battery types. • Disposable. • Rechargeable. • Storage. • Power capabilities rated in Ampere-hours. • Amps X time.

  8. Common Battery Types • Carbon Zinc 1.5V per cell Non rechargeable • Alkaline 1.5V per cell Non rechargeable • Lithium Coin 3.0 – 3.3 V Non rechargeable • Nickel Cadmium 1.2V per cell Rechargeable • NiMH 1.2v per cell Rechargeable • Lithium Ion 3.3 - 3.6V Rechargeable • Lead Acid 2 V per cell Rechargeable

  9. Battery Charging • Some batteries can be recharged, some cannot. • Use the proper charger for the battery being charged. • NiCad, NiMH, L-ion. • Batteries will wear out over time. • Best if batteries are maintained fully charged. • Over-charging will cause heating and could damage the battery.

  10. Storage Batteries • Some batteries (lead-acid) will release toxic fumes during charging so require ventilation. • Hydrogen gas is explosive • Contain sulfuric acid • Car batteries hold lots of energy – shorting a battery could cause a fire or explosion.

  11. Handheld Transceivers • Battery packs – packages of several individual rechargeable batteries connected together. • NiCad (nickel-cadmium) • NiMH (nickel-metal hydride) • Li-ion (lithium-ion) • For emergencies, have a battery pack that can use disposable batteries (AA size)

  12. Which is a good reason to use a regulated power supply for communications equipment? (T4A03) • A. It prevents voltage fluctuations from reaching sensitive circuits • B. A regulated power supply has FCC approval • C. A fuse or circuit breaker regulates the power • D. Power consumption is independent of load

  13. Which is a good reason to use a regulated power supply for communications equipment? (T4A03) • A. It prevents voltage fluctuations from reaching sensitive circuits • B. A regulated power supply has FCC approval • C. A fuse or circuit breaker regulates the power • D. Power consumption is independent of load

  14. What is the source of a high-pitched whine that varies with engine speed in a mobile transceiver’s receive audio? (T4A10) • A. The ignition system • B. The alternator • C. The electric fuel pump • D Anti-lock braking system controllers

  15. What is the source of a high-pitched whine that varies with engine speed in a mobile transceiver’s receive audio? (T4A10) • A. The ignition system • B. The alternator • C. The electric fuel pump • D Anti-lock braking system controllers

  16. Where should a mobile transceiver’s power negative connection be made? (T4A11) • A. At the battery or engine block ground strap • B. At the antenna mount • C. To any metal part of the vehicle • D. Through the transceiver’s mounting bracket

  17. Where should a mobile transceiver’s power negative connection be made? (T4A11) • A. At the battery or engine block ground strap • B. At the antenna mount • C. To any metal part of the vehicle • D. Through the transceiver’s mounting bracket

  18. How much voltage does a mobile transceiver usually require? (T5A06) • A. About 12 volts • B. About 30 volts • C. About 120 volts • D. About 240 volts

  19. How much voltage does a mobile transceiver usually require? (T5A06) • A. About 12 volts • B. About 30 volts • C. About 120 volts • D. About 240 volts

  20. What is the nominal voltage of a fully charged nickel-cadmium cell? (T6A10) • A. 1.0 volts • B. 1.2 volts • C. 1.5 volts • D. 2.2 volts

  21. What is the nominal voltage of a fully charged nickel-cadmium cell? (T6A10) • A. 1.0 volts • B. 1.2 volts • C. 1.5 volts • D. 2.2 volts

  22. Which battery type is not rechargeable? (T6A11) • A. Nickel-cadmium • B. Carbon-zinc • C. Lead-acid • D. Lithium-ion

  23. Which battery type is not rechargeable? (T6A11) • A. Nickel-cadmium • B. Carbon-zinc • C. Lead-acid • D. Lithium-ion

  24. What type of circuit controls the amount of voltage from a power supply? (T6D05) • A. Regulator • B. Oscillator • C. Filter • D. Phase inverter

  25. What type of circuit controls the amount of voltage from a power supply? (T6D05) • A. Regulator • B. Oscillator • C. Filter • D. Phase inverter

  26. What could be happening if another operator reports a variable high-pitched whine on the audio from your mobile transmitter? (T7B09) • A. Your microphone is picking up noise from an open window • B. You have the volume on your receiver set too high • C. You need to adjust your squelch control • D. Noise on the vehicle’s electrical system is being transmitted along with your speech audio

  27. What could be happening if another operator reports a variable high-pitched whine on the audio from your mobile transmitter? (T7B09) • A. Your microphone is picking up noise from an open window • B. You have the volume on your receiver set too high • C. You need to adjust your squelch control • D. Noise on the vehicle’s electrical system is being transmitted along with your speech audio

  28. What is one way to recharge a 12-volt lead-acid station battery if the commercial power is out? (T0A08) • A. Cool the battery in ice for several hours • B. Add acid to the battery • C. Connect the battery to a car’s battery and run the engine • D. All of these choices are correct

  29. What is one way to recharge a 12-volt lead-acid station battery if the commercial power is out? (T0A08) • A. Cool the battery in ice for several hours • B. Add acid to the battery • C. Connect the battery to a car’s battery and run the engine • D. All of these choices are correct

  30. What kind of hazard is presented by a conventional 12-volt storage battery? (T0A09) • A. It emits ozone which can be harmful to the atmosphere • B. Shock hazard due to high voltage • C. Explosive gas can collect if not properly vented • D. All of these choices are correct

  31. What kind of hazard is presented by a conventional 12-volt storage battery? (T0A09) • A. It emits ozone which can be harmful to the atmosphere • B. Shock hazard due to high voltage • C. Explosive gas can collect if not properly vented • D. All of these choices are correct

  32. What can happen if a lead-acid storage battery is charged or discharged too quickly? (T0A10) • A. The battery could overheat and give off flammable gas or explode • B. The voltage can become reversed • C. The “memory effect” will reduce the capacity of the battery • D. All of these choices are correct

  33. What can happen if a lead-acid storage battery is charged or discharged too quickly? (T0A10) • A. The battery could overheat and give off flammable gas or explode • B. The voltage can become reversed • C. The “memory effect” will reduce the capacity of the battery • D. All of these choices are correct

  34. Radio Frequency Interference (RFI) • Unwanted, unintentional signals from some electronic device that interferes with radio wave reception. • You can help prevent creating RFI by operating your transmitting equipment properly.

  35. RFI Mitigation • Filters • Filters attenuate (reduce) interfering signals – but do not totally eliminate them. • High-pass – generally on the receive side. • Passes higher frequencies, reduces lower frequencies. • Low-pass – generally on the transmit side. • Passes lower frequencies, reduces higher frequencies.

  36. RFI Mitigation • Filters • Band-pass – used within most radio equipment. • Passes a specific range of frequencies, and rejects all others. • Band-reject – notches out a range of frequencies, and passes others. • Ferrite chokes can block unwanted RF.

  37. Types of RFI • Direct Detection – offending signals get into the electronics circuits to cause interference. • Fundamental Overload – a strong signal that overwhelms the weaker, wanted signal. • Harmonics – even number multiples of the wanted signal that cause interference. • Spurious Emissions – unwanted emissions from a radio or electronic equipment.

  38. Cable TV Interference • Usually the result of broken shielding somewhere in the cable. • Loose connections. • Broken connections. • Corroded connections. • Usually solved by proper cable maintenance by cable supplier. • If the subscriber is a legitimate subscriber.

  39. Noise Sources • Electrical arcs (motors, thermostats, electric fences, neon signs). • Power lines. • Motor vehicle ignitions or alternators. • Switching power supplies. • Computers, networks, and TV sets.

  40. Dealing with RFI • Make sure you operate your equipment properly. • Eliminate interference in your own home first.

  41. Dealing with RFI • Take interference complaints seriously. • Make sure that you’re really not the cause (demonstrate that you don’t interfere within your own home). • Offer to help eliminate the RFI, even if you are not at fault. • Consult ARRL RFI Resources for help and assistance.

  42. What the Rules Say • RFI from and to unlicensed devices is the responsibility of the users of such devices • Bottom line – If your station is operating properly, you are protected against interference complaints • BUT – Be a good neighbor because they may (probably) not be familiar with Part 15 rules and regulations

  43. Where must a filter be installed to reduce harmonic emissions? (T4A04) • A. Between the transmitter and the antenna • B. Between the receiver and the transmitter • C. At the station power supply • D. At the microphone

  44. Where must a filter be installed to reduce harmonic emissions? (T4A04) • A. Between the transmitter and the antenna • B. Between the receiver and the transmitter • C. At the station power supply • D. At the microphone

  45. What type of filter should be connected to a TV receiver as the first step in trying to prevent RF overload from a nearby 2 meter transmitter? (T4A05) • A. Low-pass filter • B. High-pass filter • C. Band-pass filter • D. Band-reject filter

  46. What type of filter should be connected to a TV receiver as the first step in trying to prevent RF overload from a nearby 2 meter transmitter? (T4A05) • A. Low-pass filter • B. High-pass filter • C. Band-pass filter • D. Band-reject filter

  47. Which would you use to reduce RF current flowing on the shield of an audio cable? (T4A09) • A. Band-pass filter • B. Low-pass filter • C. Preamplifier • D. Ferrite choke

  48. Which would you use to reduce RF current flowing on the shield of an audio cable? (T4A09) • A. Band-pass filter • B. Low-pass filter • C. Preamplifier • D. Ferrite choke

  49. What is meant by fundamental overload in reference to a receiver? (T7B02) • A. To much voltage from the power supply • B. Too much current from the power supply • C. Interference caused by very strong signals • D. Interference caused by turning the volume up too high

  50. What is meant by fundamental overload in reference to a receiver? (T7B02) • A. To much voltage from the power supply • B. Too much current from the power supply • C. Interference caused by very strong signals • D. Interference caused by turning the volume up too high

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