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Amateur Extra License Class. Chapter 11 Safety. Hazardous Materials. Polychlorinated Biphenyls (PCB’s) Additive to oils used as insulator in older electrical components. Large transformers. High-voltage capacitors. Known carcinogen. Hazardous Materials. Polychlorinated Biphenyls (PCB’s)

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Amateur Extra License Class

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Amateur Extra License Class

Chapter 11

Safety


Hazardous Materials

  • Polychlorinated Biphenyls (PCB’s)

    • Additive to oils used as insulator in older electrical components.

      • Large transformers.

      • High-voltage capacitors.

    • Known carcinogen.


Hazardous Materials

  • Polychlorinated Biphenyls (PCB’s)

    • Avoid skin contact.

      • Wear rubber gloves

      • Wipe down case with paper towel.

    • Properly dispose of component & materials used to handle it.


Hazardous Materials

  • Beryllium and Beryllium Oxide

    • Beryllium (Be) alloyed with copper to stiffen it & improve conductivity.

      • Spring contacts.

    • Beryllium Oxide (BeO) is a ceramic used as insulator inside vacuum tubes & semiconductors.

      • Not dangerous in solid form.

      • Known carcinogen if crushed & dust is inhaled.


Hazardous Materials

  • Lead and Soldering

    • Common solder is alloy of lead and tin.

    • Dangers from lead are:

      • Inhaling lead vapors.

        • Temperatures involved in soldering not high enough to create lead vapor. Fumes/vapors created during soldering caused by burning flux.

      • Ingestion.

        • Wash hands thoroughly before handling food.


Hazardous Materials

  • Carbon Monoxide (CO)

    • Colorless, odorless, tasteless gas.

      • Generated by incomplete combustion of fuels.

    • Can ONLY be detected by a carbon monoxide detector.

      • Ordinary smoke detectors will NOT detect CO gas.


Hazardous Materials

  • Carbon Monoxide (CO)

    • Generators & fossil fuel heaters must only be used in open, well-ventilated areas.

    • Fuel must not be stored by the generator or heater.

    • Install carbon monoxide detectors in any area occupied by people where CO gas may accumulate.


E0A07 -- How may dangerous levels of carbon monoxide from an emergency generator be detected?

By the odor

Only with a carbon monoxide detector

Any ordinary smoke detector can be used

By the yellowish appearance of the gas


E0A09 -- Which insulating material commonly used as a thermal conductor for some types of electronic devices is extremely toxic if broken or crushed and the particles are accidentally inhaled?

Mica

Zinc oxide

Beryllium Oxide

Uranium Hexaflouride


E0A10 -- What material found in some electronic components such as high-voltage capacitors and transformers is considered toxic?

Polychlorinated biphenyls

Polyethylene

Polytetrafluroethylene

Polymorphic silicon


RF Exposure

  • Ionizing and Non-Ionizing Radiation.

    • Ionizing Radiation.

      • Energy high enough to strip electrons off of atoms or break atoms apart.

        • Radioactive sources.

        • Ultra-violet light.

        • X-rays.

    • Non-ionizing radiation.

      • Insufficient energy to strip electrons off of atoms or break atoms apart.

        • Radio frequency energy.


RF Exposure

  • Ionizing and Non-Ionizing Radiation.


RF Exposure

  • Ionizing and Non-Ionizing Radiation.

    • RF at low levels is not dangerous.

      • Only dangerous when level high enough to cause heating of body tissue.

  • Power Density.

    • Heating is caused by body absorbing RF energy.

    • Intensity of RF energy is called power density.

      • Measured in mW/cm2.


RF Exposure

  • Power Density.

    • Intensity of electric (E) field & magnetic (H) field can be measured separately.

      • E field measured in V/m.

      • H field measured in A/m.

      • E field & H field can peak at different locations.

      • Field impedance varies due to ground reflections, scattering, & antenna proximity.

        • Z = E / H.


RF Exposure

  • Absorption and Limits.

    • Specific absorption rate (SAR).

      • Rate at which the body absorbs RF energy.

      • Varies with frequency & size of body part.

        • Range of highest SAR is 30 MHz to 1.3 GHz.

        • Torso & limbs -- SAR highest at VHF (30 MHz to 300 MHz).

        • Head – SAR highest at UHF (300 MHz to 3 GHz).

        • Eyes – SAR highest at microwave frequencies < 1 GHz.


RF Exposure

  • Absorption and Limits.

    • Maximum permissible exposure (MPE).

      • Highest level of exposure allowed by the regulations.


RF Exposure

  • Averaging and Duty Cycle.

    • Exposure to RF is averaged over specified time periods.

      • Body responds differently to long duration and short duration exposure.

      • Different “environments” are averaged over different time periods.

        • Controlled environment.

        • Uncontrolled environment.


RF Exposure

  • Averaging and Duty Cycle.

    • Controlled environment.

      • Areas where occupants are aware of and knowledgeable about RF exposure.

      • Exposure averaged over 6-minute period.

      • Higher MPE limits.

    • Uncontrolled environment.

      • Areas accessible to persons unaware of RF exposure.

      • Exposure averaged over 30-minute period.

      • Lower MPE limits.


RF Exposure

  • Absorption and Limits.


RF Exposure

  • Averaging and Duty Cycle.

    • Duty cycle.

      • Ratio of transmitter on time to total time during the exposure.

      • Varies with mode.

        • Transmitter is not at full output power all of the time depending on mode.

        • Typical duty cycles:

          • SSB (unprocessed) = 20% to 25%.

          • SSB (processed) = 40%.

          • FM = 100%.

          • CW = 40%.


E0A01 -- What, if any, are the differences between the radiation produced by radioactive materials and the electromagnetic energy radiated by an antenna?

There is no significant difference between the two types of radiation

Only radiation produced by radioactivity can injure human beings

Radioactive materials emit ionizing radiation, while RF signals have less energy and can only cause heating

Radiation from an antenna will damage unexposed photographic film but ordinary radioactive materials do not cause this problem


E0A02 -- When evaluating RF exposure levels from your station at a neighbor’s home, what must you do?

Make sure signals from your station are less than the controlled MPE limits

Make sure signals from your station are less than the uncontrolled MPE limits

You need only evaluate exposure levels on your own property

Advise your neighbors of the results of your tests


E0A06 -- Why are there separate electric (E) and magnetic (H) field MPE limits?

The body reacts to electromagnetic radiation from both the E and H fields

Ground reflections and scattering make the field impedance vary with location

E field and H field radiation intensity peaks can occur at different locations

All of these choices are correct


E0A08 -- What does SAR measure?

Synthetic Aperture Ratio of the human body

Signal Amplification Rating

The rate at which RF energy is absorbed by the body

The rate of RF energy reflected from stationary terrain


E0A11 -- Which of the following injuries can result from using high-power UHF or microwave transmitters?

Hearing loss caused by high voltage corona discharge

Blood clotting from the intense magnetic field

Localized heating of the body from RF exposure in excess of the MPE limits

Ingestion of ozone gas from the cooling system


RF Exposure

  • Antenna System.

    • Must take into account antenna gain if in far field.

      • Far field -- antenna pattern does not change with distance.

        • Approximately 10λ.


RF Exposure

  • Estimating Exposure and Station Evaluation.

    • All fixed amateur stations must evaluate RF exposure potential.

      • Mobile & portable stations exempt.

      • Exempt if transmitter output power is below specified limits.

        • Limits vary by frequency.

        • Only have to evaluate transmitters that exceed the specified power output limits.


RF Exposure

  • Estimating Exposure and Station Evaluation.

    • Power thresholds for RF Exposure Evaluation.


RF Exposure

  • Estimating Exposure and Station Evaluation.

    • Methods of Evaluating RF Exposure.

      • Calibrated field strength meter and antenna.

        • VERY expensive.

          • ≈ $15,000.


RF Exposure

  • Estimating Exposure and Station Evaluation.

    • Methods of Evaluating RF Exposure.

      • Calculate using formulas.

        • Use charts based on formulas.

        • Use software based on formulas.

        • Need to know:

          • Transmitter output power.

          • Feedline loss.

          • Antenna gain.

          • Antenna height above ground.

          • Frequency.


RF Exposure

  • Estimating Exposure and Station Evaluation.

    • Multi-transmitter environment.

      • All transmitter operators are jointly responsible for seeing that MPE’s are not exceeded.

      • A transmitter must be included in the site evaluation if it produces more than 5% of the MPE for that frequency.


RF Exposure

  • Exposure Safety Measures.

    • Locate antennas where people cannot get near them.

    • Don’t point antennas at occupied locations.

    • Carefully evaluate exposure from “stealth” antennas.


RF Exposure

  • Exposure Safety Measures.

    • Locate VHF/UHF mobile antennas on roof of vehicle or on trunk lid.

    • Use extra care with high-gain antennas used for VHF/UHF/microwave frequencies.


E0A03 -- Which of the following would be a practical way to estimate whether the RF fields produced by an amateur radio station are within permissible MPE limits?

Use a calibrated antenna analyzer

Use a hand calculator plus Smith-chart equations to calculate the fields

Use an antenna modeling program to calculate field strength at accessible locations

All of the choices are correct


E0A04 -- When evaluating a site with multiple transmitters operating at the same time, the operators and licensees of which transmitters are responsible for mitigating over-exposure situations?

Only the most powerful transmitter

Only commercial transmitters

Each transmitter that produces 5% or more of its MPE exposure limit at accessible locations

Each transmitter operating with a duty-cycle greater than 50%


E0A05 -- What is one of the potential hazards of using microwaves in the amateur radio bands?

Microwaves are ionizing radiation

The high gain antennas commonly used can result in high exposure levels

Microwaves often travel long distances by ionospheric reflection

The extremely high frequency energy can damage the joints of antenna structures


Questions?


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