Extra-Study/pages/E9F.md

E9F Transmission lines: characteristics of open and shorted feed lines; coax versus open wire; velocity factor; electrical length; coaxial cable dielectrics; microstrip

• E9F01 (D) What is the velocity factor of a transmission line? #card
  • A. The ratio of its characteristic impedance to its termination impedance
  • B. The ratio of its termination impedance to its characteristic impedance
  • C. The velocity of a wave in the transmission line multiplied by the velocity of light in a vacuum
  • D. The velocity of a wave in the transmission line divided by the velocity of light in a vacuum
• E9F02 (C) Which of the following has the biggest effect on the velocity factor of a transmission line? #card
  • A. The characteristic impedance
  • B. The transmission line length
  • C. The insulating dielectric material
  • D. The center conductor resistivity
• E9F03 (D) Why is the electrical length of a coaxial cable longer than its physical length? #card
  • A. Skin effect is less pronounced in the coaxial cable
  • B. Skin effect is more pronounced in the coaxial cable
  • C. Electromagnetic waves move faster in coaxial cable than in air
  • D. Electromagnetic waves move more slowly in a coaxial cable than in air
• E9F04 (B) What impedance does a 1/2-wavelength transmission line present to an RF generator when the line is shorted at the far end? #card
  • A. Very high impedance
  • B. Very low impedance
  • C. The same as the characteristic impedance of the line
  • D. The same as the output impedance of the RF generator
• E9F05 (D) What is microstrip? #card
  • A. Special shielding material designed for microwave frequencies
  • B. Miniature coax used for low power applications
  • C. Short lengths of coax mounted on printed circuit boards to minimize time delay between microwave circuits
  • D. Precision printed circuit conductors above a ground plane that provide constant impedance interconnects at microwave frequencies
• E9F06 (C) What is the approximate physical length of an air-insulated, parallel conductor transmission line that is electrically 1/2 wavelength long at 14.10 MHz? #card
  • A. 7.0 meters
  • B. 8.5 meters
  • C. 10.6 meters
  • D. 13.3 meters
• E9F07 (A) How does parallel conductor transmission line compare to coaxial cable with a plastic dielectric? #card
  • A. Lower loss
  • B. Higher SWR
  • C. Smaller reflection coefficient
  • D. Lower velocity factor
• E9F08 (D) Which of the following is a significant difference between foam dielectric coaxial cable and solid dielectric coaxial cable, assuming all other parameters are the same? #card
  • A. Foam dielectric coaxial cable has lower safe maximum operating voltage
  • B. Foam dielectric coaxial cable has lower loss per unit of length
  • C. Foam dielectric coaxial cable has higher velocity factor
  • D. All these choices are correct
• E9F09 (A) What impedance does a 1/4-wavelength transmission line present to an RF generator when the line is shorted at the far end? #card
  • A. Very high impedance
  • B. Very low impedance
  • C. The same as the characteristic impedance of the transmission line
  • D. The same as the generator output impedance
• E9F10 (C) What impedance does a 1/8-wavelength transmission line present to an RF generator when the line is shorted at the far end? #card
  • A. A capacitive reactance
  • B. The same as the characteristic impedance of the line
  • C. An inductive reactance
  • D. Zero
• E9F11 (C) What impedance does a 1/8-wavelength transmission line present to an RF generator when the line is open at the far end? #card
  • A. The same as the characteristic impedance of the line
  • B. An inductive reactance
  • C. A capacitive reactance
  • D. Infinite
• E9F12 (D) What impedance does a 1/4-wavelength transmission line present to an RF generator when the line is open at the far end? #card
  • A. The same as the characteristic impedance of the line
  • B. The same as the input impedance to the generator
  • C. Very high impedance
  • D. Very low impedance