Technician License Class

1. Technician License Class Chapter 9 Safety

2. Electrical Safety • An electrical current flowing through the human body can cause injuries in the following ways: • Heating of body tissue. • Interference with electrical function of cells. • Involuntary muscle contractions. • Heart fibrillation. • Loss of muscle control. • Can’t let go!

3. Electrical Safety • Even small currents can cause problems. • Voltages over about 30V are considered potentially dangerous.

4. Electrical Safety • Even small currents cause problems. • Voltages over about 30V are considered dangerous.

5. Electrical Safety • Avoiding contact is the most effective way of practicing electrical safety. • Most modern radio equipment uses voltages that are not as dangerous as older equipment but precautions still must be taken.

6. Electrical Safety • Turn off power when working inside equipment. • If power is required: • Remove jewelry. • Avoid unintentional touching of circuitry. • Keep one hand in pocket when working around high voltage circuits! • Make sure equipment is properly grounded and circuit protected. • Never bypass safety interlocks!

7. Electrical Safety • REMEMBER: Capacitors hold a charge even when power is off. • REMEMBER: Storage batteries are dangerous when shorted. • ALWAYS have a safety observer present when working on high-voltage equipment!

8. Responding to Electrical Injury • REMOVE POWER! • Have ON/OFF switches and circuit breakers clearly marked. • Call for help. • Learn CPR and first aid.

9. Electrical Grounding & Circuit Protection • Make sure your home is “up to code.” • Most ham equipment does not require special wiring or circuits. • Use 3-wire power cords. • Use circuit breakers, circuit breaker outlets, or Ground Fault Circuit Interrupter (GFCI) circuit breakers or outlets • Use proper fuse or circuit breaker size. • Don’t overload single outlets.

10. 120VAC Outlet Wiring • Connect black wire to brass terminal. • Hot. • Connect white wire to silver terminal. • Neutral. • Connect green or bare wire to green terminal. • Safety Ground.

11. Lightning Safety • Antennas are not struck any more frequently than trees or tall structures. • Ground all antennas & towers. • Short, direct connections. • No sharp turns. • Use lightning arrestors.

12. Lightning Safety • Disconnect antenna cables and power cords during storms. • Disconnect telephone lines from computer modems.

13. T0A01 - What is a commonly accepted value for the lowest voltage that can cause a dangerous electric shock? A. 12 volts B. 30 volts C. 120 volts D. 300 volts

14. T0A02 - How does current flowing through the body cause a health hazard? A. By heating tissue B. It disrupts the electrical functions of cells C. It causes involuntary muscle contractions D. All of these choices are correct

15. T0A03 - What is connected to the green wire in a three-wire electrical AC plug? A. Neutral B. Hot C. Safety ground D. The white wire

16. T0A06 - What is a good way to guard against electrical shock at your station? A. Use three-wire cords and plugs for all AC powered equipment B. Connect all AC powered station equipment to a common safety ground C. Use a circuit protected by a ground-fault interrupter D. All of these choices are correct

17. T0A07 - Which of these precautions should be taken when installing devices for lightning protection in a coaxial cable feedline? A. Include a parallel bypass switch for each protector so that it can be switched out of the circuit when running high power B. Include a series switch in the ground line of each protector to prevent RF overload from inadvertently damaging the protector C. Keep the ground wires from each protector separate and connected to station ground D. Ground all of the protectors to a common plate which is in turn connected to an external ground

18. T0A11 - Which of the following is good practice when installing ground wires on a tower for lightning protection? A. Put a loop in the ground connection to prevent water damage to the ground system B. Make sure that all bends in the ground wires are clean, right angle bends C. Ensure that connections are short and direct D. All of these choices are correct

19. T0A12 - What kind of hazard might exist in a power supply when it is turned off and disconnected? A. Static electricity could damage the grounding system B. Circulating currents inside the transformer might cause damage C. The fuse might blow if you remove the cover D. You might receive an electric shock from stored charge in large capacitors

20. T0A13 - What safety equipment should always be included in home-built equipment that is powered by 120V AC power circuits? A. A fuse or circuit breaker in series with the AC “hot” conductor B. An AC voltmeter across the incoming power source C. An inductor in series with the AC power source D. A capacitor across the AC power source

21. T0B10 - Which of the following is true concerning grounding conductors used for lightning protection? A. Only non-insulated wire must be used B. Wires must be carefully routed with precise right-angle bends C. Sharp bends must be avoided D. Common grounds must be avoided

22. T0B11 - Which of the following establishes grounding requirements for an amateur radio tower or antenna? A. FCC Part 97 Rules B. Local electrical codes C. FAA tower lighting regulations D. Underwriters Laboratories’ recommended practices

23. RF Exposure • Electromagnetic energy can be absorbed by physical objects and cause changes. • Type of change depends on intensity and frequency of the energy. • At best, change in temperature. • At worst, change in molecular structure.

24. RF Exposure • Non-ionizing radiation. • Only effect is heating. • Radio frequencies. • Ionizing radiation. • Strips electrons from atoms. • Ultra-violet light. • X-rays. • Gamma rays.

25. RF Exposure

26. RF Exposure • Exposure to high levels of RF can cause problems. • If precautions are taken, RF exposure is minimal and not dangerous. • Problem is RF energy can heat body tissues. • Amount of heating depends on the RF intensity and frequency.

27. RF Intensity • Power Density • Actual transmitter power. • Higher power, higher risk. • Antenna gain and proximity. • Directional antennas focus available energy. • Being physically close or standing in the beam direction increases risk.

28. RF Intensity • Power Density • Duty cycle. • The more time the power output is at high level, the higher the risk. • Mode duty cycle. • CW = ~40%. • SSB = 25% to 40%. • FM = 100%. • Digital = 100%. • Transmit time vs. receive time.

29. Antenna Proximity • Controlled Environment. • You know where people are standing in relation to your antenna and you can do something about it. • People in the controlled environment are aware of the RF exposure and are knowledgeable about the risks involved. • More power is allowed because you can make adjustments if needed.

30. Antenna Proximity • Uncontrolled Environment. • You have no idea, or have no control of people near your antenna. • People in the uncontrolled environment are not aware of the RF exposure and do not know anything about the risks involved. • Less power is allowed because you have to assume the worse case scenario.

31. RF Exposure and Frequency • When body parts act like antennas, those parts absorb RF energy at certain frequencies (wavelengths) more efficiently and increase risk. • More caution is required at some frequencies than at other frequencies.

32. RF Exposure and Frequency

33. Mode Duty Cycle • The more time the transmitter is at full power, the greater the duty cycle, and the greater the exposure.

34. RF Exposure Evaluation • All fixed stations must perform an exposure evaluation. • Several methods are available to do this. • At lower power levels, no evaluation is required. • Varies with frequency. • Example: below 50 W at VHF.

35. RF Exposure Evaluation Methods • Use tables and/or formulas found in FCC OET Bulletin 65. • Use computer modeling software. • Use calibrated equipment to directly measure the field strength. • Equipment is extremely expensive.

36. RF Exposure Reduction • Relocating antennas is one way to reduce RF exposure • Regardless of the exposure evaluation results, make sure that people cannot come into contact with your antennas. • RF burns are painful!

37. T0C01 - What type of radiation are VHF and UHF signals? A. Gamma radiation B. Ionizing radiation C. Alpha radiation D. Non-ionizing radiation

38. T0C02 - Which of the following frequencies has the lowest Maximum Permissible Exposure limit? A. 3.5 MHz B. 50 MHz C. 440 MHz D. 1296 MHz

39. T0C03 - What is the maximum power level that an amateur radio station may use at VHF frequencies before an RF exposure evaluation is required? A. 1500 watts PEP transmitter output B. 1 watt forward power C. 50 watts PEP at the antenna D. 50 watts PEP reflected power

40. T0C04 - What factors affect the RF exposure of people near an amateur radio antenna? A. Frequency and power level of the RF field B. Distance from the antenna to the person C. Radiation pattern of the antenna D. All of these choices are correct

41. T0C05 - Why do exposure limits vary with frequency? A. Lower frequency RF fields have more energy than higher frequency fields B. Lower frequency RF fields do not penetrate the human body C. Higher frequency RF fields are transient in nature D. The human body absorbs more RF energy at some frequencies than at others

42. T0C06 - Which of the following is an acceptable method to determine that your station complies with FCC RF exposure regulations? A. By calculation based on FCC OET Bulletin 65 B. By calculation based on computer modeling C. By measurement of field strength using calibrated equipment D. All of these choices are correct

43. T0C07 - What could happen if a person accidently touched your antenna while you were transmitting? A. Touching the antenna could cause television interference B. They might receive a painful RF burn C. They might develop radiation poisoning D. All of these choices are correct

44. T0C08 - Which of the following actions might amateur operators take to prevent exposure to RF radiation in excess of FCC-supplied limits? A. Relocate antennas B. Relocate the transmitter C. Increase the duty cycle D. All of these choices are correct

45. T0C09 - How can you make sure your station stays in compliance with RF safety regulations? A. By informing the FCC of any changes made in your station B. By re-evaluating the station whenever an item of equipment is changed C. By making sure your antennas have low SWR D. All of these choices are correct

46. T0C10 - Why is duty cycle one of the factors used to determine safe RF radiation exposure levels? A. It affects the average exposure of people to radiation B. It affects the peak exposure of people to radiation C. It takes into account the antenna feedline loss D. It takes into account the thermal effects of the final amplifier

47. T0C11 - What is meant by “duty cycle” when referring to RF exposure? A. The difference between lowest usable output and maximum rated output power of a transmitter B. The difference between PEP and average power of an SSB signal C. The ratio of on-air time to total operating time of a transmitted signal D. The amount of time the operator spends transmitting

48. Physical Safety • Mobile Installations. • Secure all equipment. • Place equipment where you can operate it safely while driving.

49. Physical Safety • Antenna installation. • Clear of trees and power lines. • If it falls it won’t hit anyone or cross power lines. • Minimum of 10 feet from power lines. • Towers should use proper grounding techniques.

50. Physical Safety