A loop antenna b sense antenna c quarterwave antenna

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a) loop antenna b) sense antenna c) quarterwave antenna d) parabolic antenna 448. What is heard by earphones in the ADF? a) 3 kHz beat b) 1 kHz beat c) 2 kHz beat d) 5 kHz beat 449. If two bearing are determined from a radio beacon or station over a period of a few minutes, what else must be known to determine the ship’s position? a) speed b) elapses time c) ship’s course d) any of these 450. What important point regarding-loop RDF system maintenance? a) insulation at top of loop b) clean moving contacts c) oil bearing of loop d) any of these 451. Indicate which of the following frequencies cannot be used for reliable beyond-the-horizon terrestrial communications without repeaters: a. 20 kHz b. 15 MHz c. 900 MHz d. 12 GHz 452. A ship-to-ship communications system is plagued by fading. The best solution seems to be the use of
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a. A more directional antenna b. A broadband antenna c. Frequency diversity d. Space diversity 453. A range of microwave frequencies more easily passed by the atmosphere than are the others is called a a. Window b. Critical frequency c. Gyro frequency range d. Resonance in the atmosphere 454. Frequencies in the UHF range propagate by means of a. Ground waves b. Sky waves c. Surface waves d. Space waves 455. Tropospheric scatter is used with frequencies in the following range: a. HF b. VHF c. UHF d. VLF 456. When microwave signals follow the curvature of the earth, this is known as a. The Faraday effect b. Ducting c. Tropospheric scatter d. Iosnospheric reflection 457. Helical antennas are often used for satellite tracking at VHF because of a. Troposcatter b. Superrefraction c. Ionospheric refraction d. The Faraday effect 458. _______________ consists basically of a thin film strip in intimate contact with one side of a flat dielectric substrate, with a similar thin-film ground plane conductor on the other side of the substrate. a. Strip line b. Lecher wire c. Microstrip d. Stub 459. Waveguide is a a. Device used to determine the wavelength of a signal b. Hollow metal tube used for transmission of microwave energy c. Plastic tubular transmission line for high RF network d. Braided wire used for transmission of HF 460. Transmission lines which can convey electromagnetic waves only in higher order modes are usually called a. Coaxial cable b. Twisted pair c. Power lines d. Waveguides 461. In order to reduce cross-sectional dimensions, the waveguide to use is a. Circular b. Ridge c. Rectangular d. Elliptical 462. A signal propagated in a waveguide has a full wave of electric intensity change between the two farther walls, and no component of the electric field in the direction of propagation. The mode is a. TE1,1 b. TE1,0 c. TM2,2 d. TE2,0 463. When a particular mode is excited in a waveguide, there appears an extra electric component, in the direction of propagation. The resulting mode is a. Transverse electric b. Transverse magnetic c. Longitudinal
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  • Spring '17
  • Jane Smooth
  • d., microwave

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