Radio Communications (RCOM) Practice Test

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• Which connector is commonly used for high-power RF connections?
• In CCP FALLBACK operation, which radio serves as the default for communications?
• How can you avoid erasure of internal Comsec from the APX-123 Transponder when changing its internal battery?
• Why is impedance matching crucial at RF connectors and terminations?
• Amplitude limiting in FM demodulation is used to ensure what characteristic of the signal?
• Which Net type protocol is represented by the abbreviation L?
• Which maximum values are true for A/C storage: presets and comsets?
• Bandwidth constrains data rate and channel capacity. Which equation expresses channel capacity given bandwidth B and signal-to-noise ratio?
• How do antenna gain and directivity relate to each other?
• What is the effect of polarization mismatch between transmitter and antenna, and how can it be mitigated?
• Which power settings does the VU1 support?
• If selected are you monitoring a radio even if it's pin is pulled on the CCP?
• How many comsets are supported by the A/C simultaneously?
• The IFM amplifier primarily provides which capability during SINCGARS transmissions?
• What is the total number of cryptonet variables across Vu1 and Vu2?
• Hold-up power source?
• What does the asterisk (*) indicate on the EUFD?
• VSWR is a measure of impedance mismatch on a line; it is given by which expression and is measured with which tools?
• Which modulation technique is characterized by suppressed-carrier DSB, requiring carrier recovery?
• QPSK uses how many distinct phase states in its constellation?
• What is the function of a notch filter in RF systems?
• Which component provides control and routing of all aircraft audio?
• A vector network analyzer (VNA) is used to measure what?
• What does bit error rate measure and how is it characterized?
• Which statement best describes peak envelope power (PEP) and average power in AM transmissions?
• How would you know if the IFM is turned off?
• Multipath propagation results in what effects?
• Which expression represents the Shannon-Hartley channel capacity for bandwidth B and signal-to-noise ratio S/N?
• Describe bandwidth in relation to a radio channel and how it affects data rate.
• What is a duplexer and why is it critical in repeater deployments?
• Black diamond with green square (EUFD) indicates which item?
• Which parameter indicates how much a receiver degrades the signal quality, affecting sensitivity?
• Which EMERGENCY panel option includes GUARD, XPNDR, and ZEROIZE?
• Which spread-spectrum technique uses carrier frequency hopping?
• In the Doppler shift formula f_d = (v/λ) cos θ, what does cos θ represent?
• Which figure represents the cap for comsets on the A/C?
• Which expression represents the Friis transmission equation for received power in free space?
• Which two bands of communications does Vu1 provide?
• Make sure the IDM is in _______________ before turning off the A/C.
• What is an emission mask?
• Explain the meaning of signal-to-noise ratio and its effect on communication performance.
• What is the role of Automatic Frequency Control (AFC) in a radio receiver?
• Which statement correctly describes analog modulation and digital modulation?
• How many cwyptonet variables are on the FM radios?
• Which radios can monitor guard while transmitting on any other frequency?
• If you view the COM presets page, page 1 lists which of the following?
• QPSK stands for Quadrature Phase Shift Keying; how many bits are transmitted per symbol?
• What does no dots mean on the EUFD?
• In mobile radio systems, what is handover?
• What are intermodulation products and how do they affect receiver performance?
• In free space, which equation correctly relates propagation speed v, frequency f, and wavelength λ?
• Why is circular polarization often preferred in mobile RF communications?
• What is the unit of electrical field strength used in RF exposure limits?
• What is the purpose of interleaving in digital communications?
• Under the A/C limitations, how many presets can be present at once?
• Which statement correctly contrasts AM, FM, and SSB in terms of spectral efficiency and typical uses?
• In a superheterodyne receiver, what is the role of the local oscillator?
• There are always ____ SOI days loaded on the AH-64E at any time.
• What does S21 represent in S-parameters?
• In a radio receiver, what is the primary effect of a limiter on the demodulation process?
• Where are the transponder antennas located?
• Describe image frequency and why it can cause interference in a superheterodyne receiver.
• What is a spectrum analyzer used for?
• Which statement about Automatic Gain Control (AGC) is true?
• Increasing antenna height primarily improves which aspect of coverage?
• Hold-up power is provided by five ____ volt 'C' cell batteries.
• Which two units share the whip antenna via the diplexer?
• If the pilot presses a button on his emergency panel, will that button illuminate on the CPG's emergency panel?
• Transponder antennas located where?
• Which statement correctly differentiates FHSS and DSSS?
• What is the only difference between Fm1 and Fm2?
• What does Eb/N0 physically represent?
• What is a link budget and what factors does it include?
• How does increasing the height of an antenna affect the line-of-sight range at VHF/UHF frequencies?
• What is the purpose of a guard band between channels?
• Which of the following correctly contrasts AM and FM demodulation methods?
• Which statement best describes single-sideband (SSB) modulation and its main advantage?
• What do dots with no arrow indicates on the EUFD?
• These two radios are both ARC-231 radios.
• What is the typical impedance of standard coax and why is matching important?
• What is the effect of feedline loss on system performance?
• Which control keeps your flight settings consistent after you shut down mid-flight?
• Line-of-sight (LOS) propagation is described as what?
• Which statement best defines the noise figure of a receiver?
• What is the name of the component described as the 'heart of the communication system'?
• How many cryptonet variables are there on Vu1 and Vu2?
• A green triangle on the EUFD indicates the...
• What is the difference between an isotropic radiator and a real antenna?
• In FM modulation, what does Δf represent?
• Carson's Rule: If Δf doubles while f_m remains the same, what happens to the FM bandwidth?
• What is the main advantage of using a fixed intermediate frequency in a receiver?
• How many comsets can reside on the A/C at any given moment?
• How do digital voice modes differ in network architecture and error handling among P25, DMR, and NXDN?
• What is the significance of the 2-meter and 70-centimeter amateur bands in many regions?
• In digital modulation, what does MER quantify?
• What is radio-quiet mode and why is it important in certain bands and experiments?
• In a fall back mode which microphone will work?
• Define and differentiate between AM, DSB, and DSB-SC.
• Which pair shares the whip antenna through the diplexer?
• What is spectral efficiency in communications?
• In fall back mode, which microphone will work?
• BER testing measures which of the following?
• What is the purpose of a local oscillator (LO) in a superheterodyne receiver?
• Which symbol will appear if a frequency fails to tune in the COMSET?
• Doppler shift occurs due to relative motion; which expression gives the Doppler frequency shift?
• In many regions, the 2-meter and 70-centimeter amateur bands are used for which type of communications?
• Which control keeps your flight radio configurations intact when power is momentarily interrupted during flight?
• Which statement best describes SSB in communications?
• Path loss is defined as the reduction in power with distance. Which expression represents free-space path loss?
• What is the purpose of time-domain gating in radar or pulsed radio?
• How does higher-order QAM affect bandwidth efficiency and required Eb/N0 for the same BER?
• ______ can only be created and edited on AMPS
• The reciprocity theorem for antennas states which of the following?
• Which statement describes a superheterodyne receiver and its purpose?
• Which statement best describes image frequency concept?
• RF safety exposure guidelines require limiting exposure below regulatory thresholds; consider duty cycle, distance, and shielding; compute exposure.
• What is the difference between a SMPS (switch-mode power supply) and linear supply in terms of RF noise?
• Explain modulation index for AM and peak frequency deviation for FM.
• How do you disable monitoring of a specific radio?
• In CCP FALLBACK mode, which radio becomes the default radio?
• What is the maximum number of presets the A/C can hold at one time?
• Line-of-sight propagation is commonly used for which type of links?
• The battery box is connected to the __________.
• Single-Sideband (SSB) modulation is often preferred for HF voice because it:
• What is the typical effect of amplitude limiting on demodulation of FM?
• What is the purpose of a coaxial to waveguide transition and where is it used?
• Which statement best defines Eb/N0 in digital communications?
• Fade margin in a link budget is best described as?
• S11 in S-parameters corresponds to which quantity?
• Transponder provides _____ watts to appropriate antenna when responding to interrogations.
• A higher Q factor in a resonant circuit results in:
• On the COM presets page, page 1 shows which of the following?
• If the propagation speed is constant, increasing frequency causes the wavelength to:
• What is the primary purpose of a voice scrambler or encryption in radio communications?
• On the EUFD, which label appears to indicate manual tuning?
• Which statement best explains why antenna radiation patterns are important in link design?
• What does coding gain provide in a communication system?
• What is the FM communications frequency range?
• What is the maximum number of presets that can be loaded into the A/C concurrently?
• If a frequency fails to tune in the COMSET a ______ will be present.
• Besides electric field strength in V/m, what other metrics may be used in RF exposure guidelines?
• In sampling theory, Nyquist criterion states that to avoid distortion in sampling a signal, the sampling rate must be at least twice the maximum frequency component.
• Which of the following is a correct statement about the COM presets page pagination?
• Which statement about 50-ohm RF systems is true?
• Is an IDM a transmitter?
• How does temperature affect RF components and system performance?
• If a radio is selected and its pin is pulled on the CCP, are you monitoring the radio?
• IP3 is related to amplifier linearity. Which statement is most accurate?
• Explain what a pin diode switch or transmission line switch does in RF front ends.
• What is the primary benefit of impedance matching among transmitter, feed line, and antenna?
• To stop monitoring a particular radio, what action should you take?
• What indication shows that a radio has been tuned manually on the EUFD?
• Pre-sets can't be _____________, but they can be ______________.
• What does MER indicate in a digital modulation system?
• On the EUFD, the star symbol denotes what status?
• There are ____ data ports available for each radio channel.
• Which of the following is a Net type protocol?
• In the Friis transmission equation, which variable represents distance between transmitter and receiver?
• What does the F mean on the EUFD?
• What is the purpose of the Improved Frequency Modulation (IFM) amplifier?
• Which of the following is a common RF connector type used in test equipment?
• Which platform is used to create and edit COMSETS?
• Thermal noise power in a resistor is proportional to which quantities?
• How many data ports are available for each radio channel?
• What is the Voltage Standing Wave Ratio (VSWR) and how is it related to the reflection coefficient Γ?
• What visual cue indicates the IFM is powered off?
• Which of the following best defines error vector magnitude (EVM) and what it measures?
• A solid green block on the EUFD indicates that....
• Which statement correctly describes simplex, half-duplex, and full-duplex communication?
• When a radio's pin is pulled, what is true about monitoring status?
• Coding gain in error-correcting codes is defined as?
• Where would you look to determine what radio the other crewmember is transmitting on?
• If bandwidth increases while keeping the same signal-to-noise ratio, what happens to the maximum achievable data rate?
• If the magnitude of the reflection coefficient increases, what happens to the reflected power in the line?
• How are SNR, Eb/N0, and BER related in digital communications?
• Should you apply AC power before the ARC-231 BIT is complete?
• The A/C's storage for comsets at once is what maximum count?
• How does a repeater differ from a simple transmitter in terms of functionality and coverage?
• What communication functions are available on the EMERGENCY panel?
• Which description best defines the intermediate frequency (IF) in a receiver?
• In the Shannon-Hartley theorem, if you increase the bandwidth while keeping SNR constant, how does the channel capacity change?
• What is the true statement about impedance matching?
• Which statement best describes a half-wave dipole compared with a full-wave dipole?
• Which two bands does the VU1 radio provide?
• Which statement about image interference and filter placement is correct?
• What appears on page 1 of the COM presets page?
• Carson's Rule for estimating FM bandwidth is BW ≈ 2(Δf + f_m). What do Δf and f_m represent?
• In MIMO systems, which mechanism is primarily used to improve reliability besides increasing data rates?
• How does loudness or audio frequency response of a receiver impact operator comfort and comprehension?
• How do regulatory bodies govern RF use?
• How can you re-select the previously used frequency?
• Which statement about EIRP is most accurate?
• In digital voice networks, what does error correction do?
• Explain the concept of Squelch threshold versus AGC in receivers.
• What is the typical purpose of using a low-pass filter in a transmitter or receiver chain?
• What is the purpose of a squelch circuit in a receiver?
• ARC-231 BIT takes approximately how many seconds to complete?
• Who has control of Vu1 if the CIU fails?
• Which statement accurately describes VSWR and impedance matching?
• Explain the concept of fading and multipath in radio signals, and how diversity improves reception.
• Which practice helps prevent intermodulation products in RF front ends?
• What is a primary consequence of multipath propagation?
• What is the standard unit to express bandwidth?
• FM demodulation is commonly performed using which method?
• What is a phase-locked loop and what is its role in RF receivers?
• Explain how a directional antenna pattern can increase communication range while reducing interference.
• What is an SSB modulator and why is SSB often preferred for HF voice communications?
• Explain the basic concept of QAM modulation and its use in modern digital radios.
• What action can compensate for temperature-induced drift in RF devices?
• Which radio does not offer Frequency Hopping (FH) communication?
• Define Noise Figure (NF) and its significance in receiver sensitivity.
• Which factor directly affects antenna gain?
• What is the typical characteristic impedance for RF coax?
• Which expression is the correct free-space path loss formula in decibels?
• Which factors determine the maximum practical data rate of a radio channel?
• What is MIMO and how does it increase link capacity?
• This component is a general purpose communication processor. Referred to as the "heart of the communication system."
• What is the purpose of impedance matching in RF transmission lines?
• What are Nyquist and Shannon criteria in digital communications, and how do they relate to channel capacity and BER?
• Which statement correctly differentiates a carrier signal from a modulating baseband signal?
• Which factor most directly determines the achievable wireless range for a given transmitter and receiver?
• Pair the correct maximum counts: presets on A/C and comsets on A/C.
• How does the Q factor relate to bandwidth in a resonant circuit?
• Which statement best describes the function of a preselector in a superheterodyne RF front end?
• Which of the following is NOT a common strategy to mitigate RF interference?
• How do temperature changes affect RF circuits and which design strategies mitigate it?
• In fallback mode, which microphone works?
• The RTS controls are located on which interfaces?
• What is QSL and what information is typically exchanged in a QSO confirmation?
• Which statement best describes the initial COM presets page?
• What is the purpose of a bridge or reflectometer in RF instrumentation?
• Which radios are ARC-231 radios?
• Where is the Radio Transmit Select (RTS) controls located?
• Which expression represents Johnson-Nyquist thermal noise power in a resistor?
• What is the primary benefit of using a directional antenna in RF communications?
• What are the power settings of the VU1?