Description : How do raindrops affect radio waves?
Last Answer : They can cause attenuation by scattering.
Description : How does transit time affect the relationship of the grid voltage and the plate current at high frequencies?
Last Answer : Transit time causes the grid voltage and plate current to be out of phase
Description : Which radio frequency bands use the tropospheric scattering principle for propagation of radio waves?
Last Answer : Vhf and above
Description : How is the term "temperature inversion" used when referring to radio waves?
Last Answer : It is a condition where layers of warm air are formed above layers of cool air.
Description : What are the two main sources of emi with which radio waves must compete?
Last Answer : Natural and man-made interference.
Description : There is a maximum frequency at which vertically transmitted radio waves can be refracted back to Earth. What is this maximum frequency called?
Last Answer : Critical frequency.
Description : Which layer of the atmosphere has relatively little effect on radio waves?
Last Answer : Stratosphere.
Description : What is one of the major reasons for the fading of radio waves which have been reflected from a surface?
Last Answer : Shifting in the phase relationships of the wave.
Description : How does temperature inversion affect radio transmission?
Last Answer : It can cause vhf and uhf transmission to be propagated far beyond normal line-of-sight distances.
Description : Electromagnetic waves of frequencies arbitrarily lower than 3,000 GHz, propagated in space without artificial guide. A. Space waves B. Terrestrial waves C. Mobile D. Hertzian waves
Last Answer : D. Hertzian waves
Description : Wave trap is used to trap waves of (a) power frequencies (b) higher frequencies entering generator or transformer units (c) either of the above (d) none of the above
Last Answer : (b) higher frequencies entering generator or transformer units
Description : Which of the following statements is not true with respect to microwaves? (A) Electromagnetic waves with frequencies from 300 GHz to 400 THz. (B) Propagation is line-of-sight. (C) Very ... waves cannot penetrate walls. (D) Use of certain portions of the band requires permission from authorities.
Last Answer : (A) Electromagnetic waves with frequencies from 300 GHz to 400 THz.
Description : What type of insulator works well at very high frequencies?
Last Answer : A shorted quarter-wave section called a metallic insulator.
Description : At very high frequencies, what characteristics are displayed by ordinary insulators?
Last Answer : The characteristics of the dielectric of a capacitor.
Description : . Why are coaxial lines more efficient at microwave frequencies than two-wire transmission lines?
Last Answer : The electromagnetic fields are completely confined
Description : A cavity that vibrates at its natural frequency produces a louder sound than at other frequencies. What term is used to describe this phenomenon?
Last Answer : Resonance.
Description : What type filter is used to block the passage of current for a narrow band of frequencies, while allowing current to flow at all frequencies above or below this band?
Last Answer : . Band-reject.
Description : What type filter is used to allow a narrow band of frequencies to pass through a circuit and attenuate all other frequencies above or below the desired band?
Last Answer : Bandpass.
Description : What term is used to describe the frequency at which the filter circuit changes from the point of rejecting the unwanted frequencies to the point of passing the desired frequencies?
Last Answer : Frequency cutoff (fco).
Description : What is the filter called that passes low frequencies but rejects or attenuates high frequencies?
Last Answer : Low-pass filter, high-frequency discriminator or high-frequency attenuator.
Description : What is the filter called in which the low frequencies do not produce a useful voltage?
Last Answer : High-pass filter, low-frequency discriminator, or low-frequency attenuator.
Description : What is the device called that will separate alternating current from direct current, or that will separate alternating current of one frequency from other alternating currents of different frequencies?
Last Answer : A filter.
Description : What is the band of frequencies called that is included between the two points at which current falls to 70 percent of its maximum value in a resonant circuit?
Last Answer : Bandwidth of the circuit
Description : What effect does transit time have on a conventional triode operated at uhf frequencies?
Last Answer : It causes the control grid to short to the cathode
Description : When a wide band of frequencies is transmitted simultaneously, each frequency will vary in the amount of fading. What is this variable fading called?
Last Answer : Selective fading.
Description : Receiver bandwidth is defined as those frequencies spread between what two points of the receiver response curve?
Last Answer : Half-power points.
Description : What IF frequencies are normally used in radar receivers
Last Answer : Thirty or sixty megahertz.
Description : What transmitter component allows the radiation of a large number of discrete frequencies over a wide band?
Last Answer : . Frequency synthesizer.
Description : Why do 2D air-search radars use relatively low carrier frequencies and low pulse-repetition rates?
Last Answer : Increased maximum range.
Description : Is it possible for a transmission line to operate improperly at certain frequencies and properly at others?
Last Answer : Yes, it is quite common.
Description : What device sweeps a band of frequencies to determine frequencies and amplitudes of each frequency component?
Last Answer : Spectrum analyzer.
Description : At frequencies above 100 megahertz, the intrinsic (i) region causes a pin diode to act as what?
Last Answer : Variable resistance.
Description : The cavities of a multicavity klystron are tuned to slightly different frequencies in what method of tuning?
Last Answer : Stagger tuning.
Description : When using frequencies above 30 megahertz, you are normally limited to using what range?
Last Answer : Line of sight.
Description : What frequencies are provided through the back-panel BNC?
Last Answer : 1 MHz and 10 MHz.
Description : What type of polarization should be used if an antenna is mounted on a moving vehicle at frequencies below 50 megahertz?
Last Answer : Vertical polarization.
Description : What is an advantage of using horizontal polarization at high frequencies?
Last Answer : Less interference is experienced by man-made noise sources
Description : What type of polarization should be used at medium and low frequencies?
Description : What circuit section is required in the output of a multivibrator modulator to eliminate unwanted output frequencies?
Last Answer : An LCR filter.
Description : With a single modulating tone, what is the amplitude of the sideband frequencies at 100-percent modulation?
Last Answer : One-half the amplitude of the carrier.
Description : What type of coupling is most effective at high frequencies?
Last Answer : Impedance coupling.
Description : What type of communications equipment functions as a radio receiver and searches across several frequencies?
Last Answer : What is the answer ?
Description : In cellular system, _____ defines the geographic distance that is required between cells using identical frequencies in order to avoid interference between the radio transmissions at these cells. A. frequency-reuse ratio B. distance-to-reuse ratio (D/R) C. reuse format plan ratio D. reuse factor
Last Answer : B. distance-to-reuse ratio (D/R)
Description : What device measures the angle between two radio frequencies and also the direction of propagation of a wave? A. Densimeter B. Absorption wavemeter C. Goniometer D. Ergometer
Last Answer : C. Goniometer
Description : Frequencies above ______ kHz, are referred to as the radio frequencies. A. 20 B. 2 C. 10 D. 200
Last Answer : A. 20
Description : Which of the following is designated as the international distress, safety and calling frequency for radio telephony for stations of the maritime mobile service when using frequencies in the authorized bands between 156 and 174 MHz? A. 165.8 MHz B. 156.8 MHz C. 158.6 MHz D. 168.5 MHz
Last Answer : B. 156.8 MHz
Description : kilohertz (kHz) is a unit which measures? A. Power used by a current of one ampere B. Electromagnetic radio wave frequencies (Answer) C. Voltage D. Electric resistance
Last Answer : B. Electromagnetic radio wave frequencies (Answer)
Description : Why do wave frequencies higher than visible light hurt us while others do not affect us?
Last Answer : Electromagnetic radiation in the UVB band and up are able to ionize atoms, this can cause serious biological damage.Electromagnetic radiation in the UVA band and down cannot ionize atoms. The visible light band is just below the UVA band.
Description : Compared to the velocity of propagation of waves in air, what is the velocity of propagation of waves in waveguides?
Last Answer : Slower.