A-007 — Feedlines and matching

Feedlines and matching at the advanced level: transmission line theory, impedance transformation, stubs and matching networks.

All 99 questions

• A-007-001-001 For an antenna tuner of the "Transformer" type, which of the following statements is FALSE?
• A-007-001-002 For an antenna tuner of the "Series" type, which of the following statements is false?
• A-007-001-003 For an antenna tuner of the "L" type, which of the following statements is false?
• A-007-001-004 For an antenna tuner of the "Pi" type, which of the following statements is false?
• A-007-001-005 What is a pi-network?
• A-007-001-006 Which type of network offers the greatest transformation ratio?
• A-007-001-007 Why is an L-network of limited utility in impedance matching?
• A-007-001-008 How does a network transform one impedance to another?
• A-007-001-009 What 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-007-001-010 Which type of network provides the greatest harmonic suppression?
• A-007-001-011 A Smith Chart is useful:
• A-007-002-001 What kind of impedance does a quarter wavelength transmission line present to the source when the line is shorted at the far end?
• A-007-002-002 What kind of impedance does a quarter wavelength transmission line present to the source if the line is open at the far end?
• A-007-002-003 What kind of impedance does a half wavelength transmission line present to the source when the line is open at the far end?
• A-007-002-004 What kind of impedance does a half wavelength transmission line present to the source when the line is shorted at the far end?
• A-007-002-005 What is the velocity factor of a transmission line?
• A-007-002-006 What 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-007-002-007 What is a typical velocity factor for coaxial cable with polyethylene dielectric?
• A-007-002-008 What determines the velocity factor in a transmission line?
• A-007-002-009 Why is the physical length of a coaxial cable shorter than its electrical length?
• A-007-002-010 The 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-007-002-011 The velocity factor of a transmission line is the:
• A-007-003-001 What 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-007-003-002 What 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-007-003-003 What 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-007-003-004 Assuming 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-007-003-005 The 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-007-003-006 A 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-007-003-007 The matching of a driven element with a single adjustable mechanical and capacitive arrangement is descriptive of:
• A-007-003-008 A Yagi antenna uses a gamma match. The coaxial braid connects to:
• A-007-003-009 A Yagi antenna uses a gamma match. The centre of the driven element connects to:
• A-007-003-010 A Yagi antenna uses a gamma match. The adjustable gamma rod connects to:
• A-007-003-011 A Yagi antenna uses a gamma match. The variable capacitor connects to the:
• A-007-004-001 In a half-wave dipole, the distribution of _______ is highest at each end.
• A-007-004-002 In a half-wave dipole, the distribution of _______ is lowest at each end.
• A-007-004-003 The feed point in a centre-fed half-wave antenna is at the point of:
• A-007-004-004 In a half-wave dipole, the lowest distribution of _________ occurs at the middle.
• A-007-004-005 In a half-wave dipole, the highest distribution of ________ occurs at the middle.
• A-007-004-006 A half-wave dipole antenna is normally fed at the point where:
• A-007-004-007 At the ends of a half-wave dipole:
• A-007-004-008 The impedance of a half-wave antenna at its centre is low, because at this point:
• A-007-004-009 In a half-wave dipole, where does minimum voltage occur?
• A-007-004-010 In a half-wave dipole, where does the minimum current occur?
• A-007-004-011 In a half-wave dipole, where does the minimum impedance occur?
• A-007-005-001 What is meant by circularly polarized electromagnetic waves?
• A-007-005-002 What type of polarization is produced by crossed dipoles fed 90 degrees out of phase?
• A-007-005-003 Which of these antennas does not produce circular polarization?
• A-007-005-004 On VHF/UHF frequencies, Doppler shift becomes of consequence on which type of communication?
• A-007-005-005 For VHF and UHF signals over a fixed path, what extra loss can be expected when linearly-polarized antennas are crossed-polarized (90 degrees)?
• A-007-005-006 Which of the following is NOT a valid parabolic dish illumination arrangement?
• A-007-005-007 A parabolic antenna is very efficient because:
• A-007-005-008 A helical-beam antenna with right-hand polarization will best receive signals with:
• A-007-005-009 One antenna which will respond simultaneously to vertically-and horizontally-polarized signals is the:
• A-007-005-010 In amateur work, what is the surface error upper limit you should try not to exceed on a parabolic reflector?
• A-007-005-011 You want to convert a surplus parabolic dish for amateur radio use, the gain of this antenna depends on:
• A-007-006-001 A 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-007-006-002 As standing wave ratio rises, so does the loss in the transmission line. This is caused by:
• A-007-006-003 What 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-007-006-004 Effective Radiated Power means the:
• A-007-006-005 A 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-007-006-006 A 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-007-006-007 If the overall gain of an amateur station is increased by 3 dB the ERP (Effective Radiated Power) will:
• A-007-006-008 A 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-007-006-009 If 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-007-006-010 A 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-007-006-011 A 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-007-007-001 For a 3-element Yagi antenna with horizontally mounted elements, how does the main lobe takeoff angle vary with height above flat ground?
• A-007-007-002 Most simple horizontally polarized antennas do not exhibit significant directivity unless they are:
• A-007-007-003 The plane from which ground reflections can be considered to take place, or the effective ground plane for an antenna is:
• A-007-007-004 Why 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-007-007-005 When a half-wave dipole antenna is installed one-half wavelength above ground, the:
• A-007-007-006 How does antenna height affect the horizontal (azimuthal) radiation pattern of a horizontal dipole HF antenna?
• A-007-007-007 For long distance propagation, the vertical radiation angle of the energy from the antenna should be:
• A-007-007-008 Greater distance can be covered with multiple-hop transmissions by decreasing the:
• A-007-007-009 The impedance at the centre of a dipole antenna more than 3 wavelengths above ground would be nearest to:
• A-007-007-010 Why can a horizontal antenna closer to ground be advantageous for close range communications on lower HF bands?
• A-007-007-011 Which antenna system and operating frequency are most suitable for Near Vertical Incidence (NVIS) communications?
• A-007-008-001 What is meant by the radiation resistance of an antenna?
• A-007-008-002 Why would one need to know the radiation resistance of an antenna?
• A-007-008-003 What factors determine the radiation resistance of an antenna?
• A-007-008-004 What is the term for the ratio of the radiation resistance of an antenna to the total resistance of the system?
• A-007-008-005 What is included in the total resistance of an antenna system?
• A-007-008-006 How can the approximate beamwidth of a beam antenna be determined?
• A-007-008-007 How is antenna percent efficiency calculated?
• A-007-008-008 What is the term used for an equivalent resistance which would dissipate the same amount of energy as that radiated from an antenna?
• A-007-008-009 Antenna beamwidth is the angular distance between:
• A-007-008-010 If the ohmic resistance of a half-wave dipole is 2 ohms, and the radiation resistance is 72 ohms, what is the antenna efficiency?
• A-007-008-011 If the ohmic resistance of a miniloop antenna is 2 milliohms and the radiation resistance is 50 milliohms, what is the antenna efficiency?
• A-007-009-001 Waveguide is typically used:
• A-007-009-002 Which of the following is not correct? Waveguide is an efficient transmission medium because it features:
• A-007-009-003 Which of the following is an advantage of waveguide as a transmission line?
• A-007-009-004 For rectangular waveguide to transfer energy, the cross-section should be at least:
• A-007-009-005 Which of the following statements about waveguide IS NOT correct?
• A-007-009-006 Which of the following is a major advantage of waveguide over coaxial cable for use at microwave frequencies?
• A-007-009-007 What is printed circuit transmission line called?
• A-007-009-008 Compared with coaxial cable, microstripline:
• A-007-009-009 A section of waveguide:
• A-007-009-010 Stripline is a:
• A-007-009-011 What precautions should you take before beginning repairs on a microwave feed horn or waveguide?