CA_ADV
Advanced - Interference, EMC, and safety
Interference, EMC, and safety follows the A-007 section of the Canadian question bank.
99
Questions
6
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- Advanced
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- Interference, EMC, and safety
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Review by section order to build the topic framework first.
For regulatory and safety questions, prefer compliant and conservative actions.
For calculations, check units, multipliers, and approximations.
Topic Study Guide
This topic covers section A-007 of the Canadian Advanced question bank, focusing on antenna matching networks, transmission line characteristics, Effective Radiated Power (ERP) calculations, and wave propagation with polarization.
High-Yield Checks
- Matching Networks: Master the structures and uses of Pi-networks (1 inductor/2 capacitors or vice versa), Pi-L networks (greater harmonic suppression), Gamma matches (single rod with series capacitor), and Stub matches (perpendicular transmission line).
- Transmission Lines & Velocity Factor: Velocity factor is the reciprocal of the square root of the dielectric constant; an open quarter-wave line presents very low impedance at the source.
- ERP Calculations: Be fluent in dB math (+3dB = 2x, +10dB = 10x). Always subtract feedline and tuner losses from antenna gain before calculating the multiplier.
- Propagation & Polarization: NVIS requires a horizontal antenna < 1/4 wavelength high and a frequency below the critical frequency. Cross-polarization of linear antennas causes 20+ dB loss.
Trap Patterns
- Confusing matching networks: Mixing up Gamma and T-matches, or assuming Pi-L networks improve efficiency (they actually provide better harmonic suppression).
- Missing losses in ERP: Forgetting to subtract feedline and connector dB losses before applying the multiplier to the transmitter power.
- Misjudging center voltage/current: Incorrectly assuming the center of a half-wave dipole has high voltage; it actually has low voltage and high current.
- Misunderstanding velocity factor: Confusing velocity factor with SWR, forgetting that it is determined by the dielectric constant of the insulator.
Review Steps
- Compare and memorize the component layouts and physical connections of common matching networks (Pi, Pi-L, Gamma, Stub).
- Practice dB addition/subtraction and power multiplier conversions to quickly estimate ERP without a calculator.
- Review transmission line theory, especially quarter-wave impedance transformations and how the dielectric constant affects propagation speed.
- Understand NVIS antenna setup requirements and the severe attenuation caused by polarization mismatch in practical scenarios.
Quick Checks
- What basic components make up a Pi-network?
- How should the net system gain be calculated when determining ERP?
- What is the voltage and current distribution at the center of a half-wave dipole?
- What is the primary advantage of a Pi-L network over a Pi-network?
Questions in This Topic
Choose Practice ModeA-007-001-001For an antenna tuner of the "Transformer" type, which of the following statements is FALSE?A-007-001-002For an antenna tuner of the "Series" type, which of the following statements is false?A-007-001-003For an antenna tuner of the "L" type, which of the following statements is false?A-007-001-004For an antenna tuner of the "Pi" type, which of the following statements is false?A-007-001-005What is a pi-network?A-007-001-006Which type of network offers the greatest transformation ratio?A-007-001-007Why is an L-network of limited utility in impedance matching?A-007-001-008How does a network transform one impedance to another?A-007-001-009What advantage does a pi-L network have over a pi-network for impedance matching between a vacuum tube linear amplifier and a multiband antenna?A-007-001-010Which type of network provides the greatest harmonic suppression?A-007-001-011A Smith Chart is useful:A-007-002-001What kind of impedance does a quarter wavelength transmission line present to the source when the line is shorted at the far end?A-007-002-002What kind of impedance does a quarter wavelength transmission line present to the source if the line is open at the far end?A-007-002-003What kind of impedance does a half wavelength transmission line present to the source when the line is open at the far end?A-007-002-004What kind of impedance does a half wavelength transmission line present to the source when the line is shorted at the far end?A-007-002-005What is the velocity factor of a transmission line?A-007-002-006What is the term for the ratio of the actual velocity at which a signal travels through a transmission line to the speed of light in a vacuum?A-007-002-007What is a typical velocity factor for coaxial cable with polyethylene dielectric?A-007-002-008What determines the velocity factor in a transmission line?A-007-002-009Why is the physical length of a coaxial cable shorter than its electrical length?A-007-002-010The reciprocal of the square root of the dielectric constant of the material used to separate the conductors in a transmission line gives the ____________ of the line:A-007-002-011The velocity factor of a transmission line is the:A-007-003-001What term describes a method used to match a high-impedance transmission line to a lower impedance antenna by connecting the line to the driven element in two places, spaced a fraction of a wavelength on each side of the driven element centre?A-007-003-002What term describes an unbalanced feed system in which the driven element of an antenna is fed both at the centre and a fraction of a wavelength to one side of centre?A-007-003-003What term describes a method of antenna impedance matching that uses a short section of transmission line connected to the antenna transmission line near the antenna and perpendicular to the transmission line?A-007-003-004Assuming a velocity factor of 0.66 what would be the physical length of a typical coaxial stub that is electrically one quarter wavelength long at 14.1 MHz?A-007-003-005The driven element of a Yagi antenna is connected to a coaxial transmission line. The coax braid is connected to the centre of the driven element and the centre conductor is connected to a variable capacitor in series with an adjustable mechanical arrangement on one side of the driven element. The type of matching is:A-007-003-006A quarter-wave stub, for use at 15 MHz, is made from a coaxial cable having a velocity factor of 0.8. Its physical length will be:A-007-003-007The matching of a driven element with a single adjustable mechanical and capacitive arrangement is descriptive of:A-007-003-008A Yagi antenna uses a gamma match. The coaxial braid connects to:A-007-003-009A Yagi antenna uses a gamma match. The centre of the driven element connects to:A-007-003-010A Yagi antenna uses a gamma match. The adjustable gamma rod connects to:A-007-003-011A Yagi antenna uses a gamma match. The variable capacitor connects to the:A-007-004-001In a half-wave dipole, the distribution of _______ is highest at each end.A-007-004-002In a half-wave dipole, the distribution of _______ is lowest at each end.A-007-004-003The feed point in a centre-fed half-wave antenna is at the point of:A-007-004-004In a half-wave dipole, the lowest distribution of _________ occurs at the middle.A-007-004-005In a half-wave dipole, the highest distribution of ________ occurs at the middle.A-007-004-006A half-wave dipole antenna is normally fed at the point where:A-007-004-007At the ends of a half-wave dipole:A-007-004-008The impedance of a half-wave antenna at its centre is low, because at this point:A-007-004-009In a half-wave dipole, where does minimum voltage occur?A-007-004-010In a half-wave dipole, where does the minimum current occur?A-007-004-011In a half-wave dipole, where does the minimum impedance occur?A-007-005-001What is meant by circularly polarized electromagnetic waves?A-007-005-002What type of polarization is produced by crossed dipoles fed 90 degrees out of phase?A-007-005-003Which of these antennas does not produce circular polarization?A-007-005-004On VHF/UHF frequencies, Doppler shift becomes of consequence on which type of communication?A-007-005-005For VHF and UHF signals over a fixed path, what extra loss can be expected when linearly-polarized antennas are crossed-polarized (90 degrees)?A-007-005-006Which of the following is NOT a valid parabolic dish illumination arrangement?A-007-005-007A parabolic antenna is very efficient because:A-007-005-008A helical-beam antenna with right-hand polarization will best receive signals with:A-007-005-009One antenna which will respond simultaneously to vertically- and horizontally-polarized signals is the:A-007-005-010In amateur work, what is the surface error upper limit you should try not to exceed on a parabolic reflector?A-007-005-011You want to convert a surplus parabolic dish for amateur radio use, the gain of this antenna depends on:A-007-006-001A transmitter has an output of 100 watts. The cable and connectors have a composite loss of 3 dB, and the antenna has a gain of 6 dBd. What is the Effective Radiated Power?A-007-006-002As standing wave ratio rises, so does the loss in the transmission line. This is caused by:A-007-006-003What is the Effective Radiated Power of an amateur transmitter, if the transmitter output power is 200 watts, the transmission line loss is 5 watts, and the antenna power gain is 3 dBd?A-007-006-004Effective Radiated Power means the:A-007-006-005A transmitter has an output power of 200 watts. The coaxial and connector losses are 3 dB in total, and the antenna gain is 9 dBd. What is the approximate Effective Radiated Power of this system?A-007-006-006A transmitter has a power output of 100 watts. There is a loss of 1.30 dB in the transmission line, a loss of 0.2 dB through the antenna tuner, and a gain of 4.50 dBd in the antenna. The Effective Radiated Power (ERP) is:A-007-006-007If the overall gain of an amateur station is increased by 3 dB the ERP (Effective Radiated Power) will:A-007-006-008A transmitter has a power output of 125 watts. There is a loss of 0.8 dB in the transmission line, 0.2 dB in the antenna tuner, and a gain of 10 dBd in the antenna. The Effective Radiated Power (ERP) is:A-007-006-009If a 3 dBd gain antenna is replaced with a 9 dBd gain antenna, with no other changes, the Effective Radiated Power (ERP) will increase by:A-007-006-010A transmitter has an output of 2000 watts PEP. The transmission line, connectors and antenna tuner have a composite loss of 1 dB, and the gain from the stacked Yagi antenna is 10 dBd. What is the Effective Radiated Power (ERP) in watts PEP?A-007-006-011A transmitter has an output of 1000 watts PEP. The coaxial cable, connectors and antenna tuner have a composite loss of 1 dB, and the antenna gain is 10 dBd. What is the Effective Radiated Power (ERP) in watts PEP?A-007-007-001For a 3-element Yagi antenna with horizontally mounted elements, how does the main lobe takeoff angle vary with height above flat ground?A-007-007-002Most simple horizontally polarized antennas do not exhibit significant directivity unless they are:A-007-007-003The plane from which ground reflections can be considered to take place, or the effective ground plane for an antenna is:A-007-007-004Why is a ground-mounted vertical quarter-wave antenna in reasonably open surroundings better for long distance contacts than a half-wave dipole at a quarter wavelength above ground?A-007-007-005When a half-wave dipole antenna is installed one-half wavelength above ground, the:A-007-007-006How does antenna height affect the horizontal (azimuthal) radiation pattern of a horizontal dipole HF antenna?A-007-007-007For long distance propagation, the vertical radiation angle of the energy from the antenna should be:A-007-007-008Greater distance can be covered with multiple-hop transmissions by decreasing the:A-007-007-009The impedance at the centre of a dipole antenna more than 3 wavelengths above ground would be nearest to:A-007-007-010Why can a horizontal antenna closer to ground be advantageous for close range communications on lower HF bands?A-007-007-011Which antenna system and operating frequency are most suitable for Near Vertical Incidence (NVIS) communications?A-007-008-001What is meant by the radiation resistance of an antenna?A-007-008-002Why would one need to know the radiation resistance of an antenna?A-007-008-003What factors determine the radiation resistance of an antenna?A-007-008-004What is the term for the ratio of the radiation resistance of an antenna to the total resistance of the system?A-007-008-005What is included in the total resistance of an antenna system?A-007-008-006How can the approximate beamwidth of a beam antenna be determined?A-007-008-007How is antenna percent efficiency calculated?A-007-008-008What is the term used for an equivalent resistance which would dissipate the same amount of energy as that radiated from an antenna?A-007-008-009Antenna beamwidth is the angular distance between:A-007-008-010If the ohmic resistance of a half-wave dipole is 2 ohms, and the radiation resistance is 72 ohms, what is the antenna efficiency?A-007-008-011If the ohmic resistance of a miniloop antenna is 2 milliohms and the radiation resistance is 50 milliohms, what is the antenna efficiency?A-007-009-001Waveguide is typically used:A-007-009-002Which of the following is not correct? Waveguide is an efficient transmission medium because it features:A-007-009-003Which of the following is an advantage of waveguide as a transmission line?A-007-009-004For rectangular waveguide to transfer energy, the cross-section should be at least:A-007-009-005Which of the following statements about waveguide IS NOT correct?A-007-009-006Which of the following is a major advantage of waveguide over coaxial cable for use at microwave frequencies?A-007-009-007What is printed circuit transmission line called?A-007-009-008Compared with coaxial cable, microstripline:A-007-009-009A section of waveguide:A-007-009-010Stripline is a:A-007-009-011What precautions should you take before beginning repairs on a microwave feed horn or waveguide?