Radio Theory Practice Test

These questions are part of the practice quiz. Start practicing

• In the wavelength calculation for meters, which speed is used in the numerator?
• What is a ground (or surface) wave?
• What formula is used to calculate the length of a 1/4 wavelength whip antenna for a frequency in MHz?
• What is the role of the amplifier in a radio transmitter?
• What is a space wave?
• What is the primary purpose of forward error correction (FEC) in digital radio?
• Which issues are more pronounced in direct-conversion (zero-IF) receivers?
• Which propagation mode involves reflection off the ionosphere to reach distant locations?
• Convert a 1000:1 power ratio to decibels.
• What is the RF spectrum?
• Define return loss and explain its relationship to VSWR.
• Which is NOT one of the three paths a radio wave travels when transmitted from an antenna?
• Carson's rule estimates FM bandwidth as BW ≈ 2(Δf + f_m). What do Δf and f_m represent?
• FM demodulation using a PLL can suffer if capture is poor. In that context, capture is influenced by sufficient frequency deviation and SNR; what is the practical consequence of poor capture?
• Which RF connector types (SMA, N, BNC) correspond to typical frequency and power handling ranges, in general terms?
• What is the primary method of demodulation used by AM receivers compared with FM receivers?
• The frequency 120 MHz lies in which RF band?
• What is the effect of increasing the order of QAM on BER at a fixed SNR?
• What is the voltage range for a common electrostatic discharge (ESD)?
• AM demodulation is accomplished using which device?
• In FM broadcasting, why is 200 kHz channel spacing used and what is the typical peak frequency deviation for the modulated signal?
• What does the audio amplifier do in a radio receiver?
• What does scattering refer to in RF signals?
• What is the primary function of a radio transmitter?
• What phenomenon occurs on a transmission line when there is a load mismatch?
• Solar flares on RF communications can cause what?
• What is a non-resonant antenna?
• Which statement about radio waves is true?
• What is absorption in RF signals?
• In what unit is frequency measured?
• Which statement about EMI categories is true?
• Which statement best describes radiation resistance in an antenna?
• Envelope detection works best when a carrier is present; AM includes carrier; easier demod. Which option correctly states this idea?
• What is electromagnetic energy (EME)?
• What does VSWR stand for?
• What does the antenna do in a radio transmitter?
• The frequency 5 MHz lies in which RF band?
• What does VSWR stand for?
• What type of antenna propagates signals in all directions?
• What is the primary use of radio waves?
• What does QAM stand for, and what does it combine?
• What is the role of the return or ground element in an antenna?
• Which statement best describes the effect of increasing modulation order on spectral efficiency when comparing QPSK to BPSK?
• What is the primary function of the audio signals in a radio transmission?
• What is downfade in RF signals?
• In receive mode, what does an antenna do with incoming electromagnetic energy?
• Which of the following is a basic resonant form of antennas?
• What is the purpose of the transmission line in a radio transmitter?
• In a radio transmission, what is the role of the audio component?
• Why is receiver sensitivity a required specification in a link budget?
• Which unit is used to express frequency in RF communications?
• For a transmission line, how does a load mismatch affect the standing wave pattern and reflected power?
• Which description best captures an isotropic antenna?
• What is the primary function of a radio receiver?
• Which modulation method is less affected by EMI and provides a clearer signal?
• What is the purpose of the keying device in a transmitter?
• Which formula correctly calculates wavelength in meters from frequency in hertz?
• How are radio waves represented?
• Which statement best describes power handling capabilities of coax versus waveguides?
• In a simple field expedient antenna, which item serves as the radiating element?
• In a classic superheterodyne receiver, what is the role of the local oscillator (LO) and the intermediate frequency (IF)?
• Which set of phenomena is listed as affecting radio wave propagation?
• What is the wavelength range of radio waves?
• Which of the following is an example of electromagnetic waves according to the list?
• What is reflection in RF signals?
• Explain the basic concept of QAM and why increasing the order (e.g., 16-QAM, 64-QAM) demands higher SNR.
• How do electric and magnetic fields behave in a radio wave?
• Which expression defines the reflection coefficient Γ for a load ZL on a transmission line with characteristic impedance Z0?
• EMI making AM signals prone to static is an example of what interference concept?
• Which of the following best describes the typical frequency service for coax versus waveguides?
• Which term describes an antenna designed to operate effectively over a wide frequency range?
• In a classic superheterodyne receiver, what is the image frequency?
• When a magnetic field changes, what is the resulting electric field orientation relative to the magnetic field?
• What is the impact of electromagnetic interference on AM signals?
• Compare superheterodyne and direct-conversion (zero-IF) receivers with respect to image frequency, DC offset, and 1/f noise issues.
• Which statement best describes Electromagnetic Compatibility (EMC) in practice?
• What is the purpose of shielding in RF design, and how does a good ground plane influence antenna performance?
• The frequency 25 MHz lies in which RF band?
• In AM, why are there two symmetric sidebands, and how does modulation index affect their amplitude distribution?
• Which propagation mode dominates the VHF and UHF bands?
• Which function best describes what the detector accomplishes with the incoming signal?
• In intermodulation terminology, which orders correspond to the sum and difference components from two tones?
• Which statement correctly describes the bandwidth difference between AM and FM transmissions?
• What is Electromagnetic Compatibility (EMC)?
• What happens if the antenna and transmitter are not matched?
• What is Phase Modulation (PM)?
• What is the main advantage of single-sideband (SSB) over conventional AM for voice communication, and what additional requirement does SSB demodulation impose on the receiver?
• In amplitude modulation, how is peak envelope power (PEP) related to carrier power and modulation index?
• Which component of a radio receiver captures radio waves?
• At resonance, a center-fed half-wave dipole has an input impedance of about 73 Ω. How does strong coupling to nearby conductors affect it?
• A center-fed half-wave dipole resonates at 100 MHz. What is its approximate free-space length?
• What is the wavelength of a 60 MHz radio wave?
• What is the electrical length of a quarter-wave transformer used for impedance matching?
• What is the relationship between electric and magnetic fields in radio waves?
• Which statement accurately describes the frequency range of radio waves?
• What is the role of preventive maintenance in achieving EMC?
• What is the skip distance in sky waves?
• Which propagation mode is capable of long-distance communication by reflecting off the ionosphere?
• Which of the following is NOT listed as an operational technique to attain EMC?
• What is the wavelength of a radio wave at a frequency of 30 MHz?
• Modulation in radio communications is used to?
• In near-field coupling between an antenna and its feed line, reactive interactions primarily cause impedance to change in the near-field region.
• What is radiation resistance and how does it relate to total input resistance of an antenna?
• On a spectrum analyzer, differentiate between resolution bandwidth (RBW) and video bandwidth (VBW) and their effect on measurement accuracy.
• Which component of a radio transmitter provides electrical power?
• Which of the following pairs correctly identifies linear polarization types?
• What does frequency measure in a sine wave?
• What is the significance of the electromagnetic wave structure?
• In an FM receiver, what is the function of the discriminator?
• In RF systems, what is the practical impact of phase noise on a digital communication link?
• Which formula correctly calculates wavelength in feet from frequency in hertz?
• Which types of information can be contained in the radio waves generated by a transmitter?
• What affects the propagation of radio waves?
• Preventive maintenance helps achieve EMC by preventing what?
• For a 50 Ω transmission line terminated with ZL = 25 Ω, which option correctly states Γ and SWR?
• Which item is not typically listed as part of a field expedient antenna?
• What is the significance of impedance matching in radio transmission?
• What is the function of the tuner in a radio receiver?
• In RF communications, what does the term 'band' refer to?
• What is the purpose of a Bird Antenna Tester / VSWR meter?
• Which of the following is NOT a basic resonant form of antennas?
• Which component in a transmitter is primarily responsible for transforming an electrical signal into radiated waves?
• What is refraction in RF signals?
• What does the detector do in a radio receiver?
• In a two-tone intermodulation test, which metrics are typically reported?
• What materials are typically needed for constructing a field expedient antenna?
• What is a sky (skip) wave?
• Which propagation mode is primarily used for long-range shortwave communications due to ionospheric reflection?
• What is diffraction in RF signals?
• Which statement about frequency units is true?
• In a Yagi-Uda antenna, what are the roles of a director and a reflector, and how do they influence forward gain?
• If you double the bandwidth from 1 Hz to 2 Hz at the same temperature, what happens to the thermal noise power in the same system?
• What is a resonant antenna?
• What is the frequency range of radio frequency (RF) waves?
• Which equation correctly expresses the relationship between speed, frequency, and wavelength for electromagnetic waves in free space?
• In an FM radio receiver, which component is used to demodulate the signal?
• Which term describes interference that degrades the operational capability of personnel, equipment, and ordinance?
• Define intermodulation distortion (IMD) and explain why it is problematic in RF receivers with multiple strong signals.
• Which speed value is given for electromagnetic energy in coax cables?
• What do S-parameters S11 and S21 represent in RF networks, and how are they typically expressed?
• What is antenna gain typically specified in?
• Which option lists the two main types of modulation used in radio transmission?
• Which factors govern the ionospheric HF reflection height and skip distance?
• Which statement correctly describes QPSK compared to BPSK?
• Which option lists the four commonly used bands for radio communications?
• Define spectral efficiency and explain how higher-order modulation affects required SNR and BER.
• How does an envelope detector recover the modulating signal from an AM waveform, and what modulation-index-related limitation does it have?
• SWR can be computed from the reflection coefficient magnitude |Γ| using which formula?
• Which statement about FM bandwidth relative to AM is true?
• What does E3 stand for in RF theory?
• What is a field expedient antenna?
• Which of the following is a practical, widely recommended mitigation for coax connector overheating when delivering high RF power?
• What frequency range is classified as Very High Frequency (VHF)?
• Wavelength is defined as what in relation to radio waves?
• In an AM communication system, which component recovers the original message from the modulated carrier?
• Which statement correctly describes a resonant antenna?
• If the frequency of a radio wave is doubled, what happens to its wavelength according to the standard relationship?
• What does modulation refer to in radio theory?
• In the RF spectrum, what unit is used to express the range of frequencies?
• What are the two types of electromagnetic interference (EMI)?
• Why is polarization matching important in RF links, and what happens if transmit and receive polarizations are orthogonal?
• In filter design, what happens to the selectivity when the Q factor increases in an LC-based band-pass filter?
• To stabilize impedance in near-field coupling, which measure is recommended?
• What are basic RF safety considerations when working with high-power RF systems?
• What happens if the SWR reading is 2:1 or worse?
• Which device in the receiver chain is responsible for making the faint signal audible by increasing its level?
• What is the role of modulation in radio communications?
• When an electric field changes, what is the induced magnetic field in relation to the electric field?
• What is Electromagnetic Interference (EMI)?
• For a simple LC band-pass design around 14.2 MHz with a 100 kHz bandwidth, what is the approximate Q required?
• What is an isotropic antenna?
• What is the adjusted speed of electromagnetic energy in coax or antenna wire?
• FM's bandwidth is typically wider, which uses more RF Spectrum. Which option states this correctly?
• Compared to AM, FM encodes information in which way, and how does noise performance compare?
• The frequency 400 MHz lies in which RF band?
• What are radio waves?
• What is a link budget and what are its main components?
• Which modulation method is cheaper to produce and requires less power?
• What practical action is required at the receiver for DSB-SC to demodulate properly that is not required for standard AM?
• How does circular polarization help mitigate polarization mismatch due to unpredictable antenna orientation?
• What is the thermal noise power in a 1 Hz bandwidth at room temperature (290 K)? Use k = 1.38×10^-23 J/K.
• What is the speed of light in a perfect world (vacuum)?
• If a received carrier is -60 dBm and the thermal floor in 1 Hz bandwidth is -100 dBm, what is the SNR in dB?
• In free space, which factor is used to determine wavelength from a given frequency?
• What does the oscillator in a radio transmitter do?
• Compared to a simple RC filter, a resonant LC band-pass filter offers which combination of Q, selectivity, and insertion loss?
• In FM demodulation, what are the roles of a slope detector and a PLL?
• What is the function of the modulator in a radio transmitter?
• What is Electrostatic Discharge (ESD)?
• What is a good SWR reading?
• Define noise figure (NF) and describe its role in predicting the overall noise performance of a RF receiver chain.
• Which coding scheme is commonly used for strong burst-error correction in data streams?
• Which statement correctly contrasts DSB-SC with conventional AM in terms of carrier presence and receiver demodulation?
• What is the effect of increasing front-end filter sharpness on SNR and group delay, and what is the typical trade-off?
• Define standing wave ratio (SWR) and show its relation to the magnitude of the reflection coefficient Γ.
• In a PLL-based frequency synthesizer, identify the main sources of phase noise and how they propagate to the RF output.
• For impedance matching between a 50 Ω source and a 25 Ω load at a single frequency, which approach is correct and what Z0 is required for a quarter-wave transformer?
• Why is SOLT calibration important for a network analyzer and what does SOLT stand for?
• The transfer of static charge between bodies due to contact or an electrostatic field is called?
• What is the purpose of the return or ground element in an antenna system?
• What is the significance of the electromagnetic (EM) spectrum?
• What frequency range is classified as Ultra High Frequency (UHF)?
• Name some operational techniques to attain EMC.
• Approximately how many feet per second is the speed of light?
• Which of the following statements best characterizes a ground wave?
• Coaxial cables and waveguides differ in typical frequency ranges, loss mechanisms, and power handling. Which statement is correct?
• Antenna gain expressed in dBi is measured relative to what reference?
• Which characteristic is typical of a semi-directional antenna such as the ones listed?
• Which of the following is an element of E3?
• The frequency 900 MHz lies in which RF band?
• Which statement is true about FM in terms of spectrum usage?
• FM has a disadvantage described as wider bandwidth requiring more RF spectrum. Which option states this disadvantage?
• In a Yagi-Uda antenna, how do the lengths of the reflector and directors compare to the driven element?
• Which term describes an antenna that has a narrow beam allowing highly directional propagation?
• AM is typically associated with which advantage?
• What frequency range is classified as High Frequency (HF)?
• Which statement is true about AM in relation to EMI?
• Name a type of semi-directional antenna.
• What is the role of the RF amplifier in a radio receiver?
• What are the two types of linear polarization?
• What is a Carrier Wave (CW)?
• What are common types of Phase Modulation?
• What is the relationship between directivity, gain, and efficiency in antenna performance?
• Which statement is true regarding AM compared to FM in terms of power and length of reach?