Description : When using frequencies above 30 megahertz, you are normally limited to using what range?
Last Answer : Line of sight.
Description : A surface-search radar normally scans how many degrees of azimuth?
Last Answer : 360 degrees.
Description : What is the most commonly used intermediate frequency of radar receivers? A. 40 MHz B. 60 MHz C. 70 MHz D. 30 MHz
Last Answer : D. 30 MHz
Description : Radar is used to (1) locate submerged submarines. (2) receive signal from radio receivers. (3) detect and locate distant objects. (4) locate geostationary satellites.
Last Answer : detect and locate distant objects
Description : What is the disadvantage of using a double receiver instead of two individual receivers?
Last Answer : If one of the receivers goes bad the entire unit must be replaced.
Description : What is the most probable cause of trouble in a synchro system that has all of its receivers reading incorrectly?
Last Answer : The transmitter or main bus.
Description : What is the greatest limiting factor in a receiver’s detectable range
Last Answer : Noise.
Description : What are the two basic types of preamplifiers used in fiber optic receivers?
Last Answer : The high-impedance amplifier and the transimpedance amplifier.
Description : Why do earth terminals require highly sensitive receivers?
Last Answer : To overcome satellite transmitter low power and permit extraction of the desired information from the received signal.
Description : Which band of frequencies used by military for its satellites and radar? A. C band B. X band C. L band D. P band
Last Answer : B. X band
Description : Which of the following frequencies is normally used for distress and safety communications? A. 4209.5 kHz B. 490 kHz C. 518 kHz D. 2174.5 kHz
Last Answer : D. 2174.5 kHz
Description : What instrument normally measures the virtual height of ionosphere? A. Ionosonde B. Altimeter C. Field meter D. Radar
Last Answer : A. Ionosonde
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 : How does fog affect radio waves at frequencies above 2 gigahertz?
Last Answer : It can cause attenuation by absorbtion.
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 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 : 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 : 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 is the normal source of dry air for a radar system?
Last Answer : Ship's central dry-air system
Description : The peak power of a radar depends on the interrelationship of what other factors?
Last Answer : Average power, pulse width, and prt.
Description : The ideal radar spectrum has what relationship to the carrier frequency?
Last Answer : Symmetrical above and below the carrier frequency.
Description : The spectrum of a radar transmitter describes what characteristic of the output pulse?
Last Answer : Frequency distribution
Description : Which of the two types of automatic gain control, agc or iagc, is most effective in radar use for the Navy?
Last Answer : IAGC.
Description : What type of receiver is most often used in radar systems?
Last Answer : Superheterodyne.
Description : What type of modulator is most commonly used in modern radar systems?
Last Answer : Line-pulsed.
Description : In an externally synchronized radar, what determines the prr of the transmitter?
Last Answer : The master oscillator.