CRAC Bilingual Manual: Emission Classes | 发射类别 (49 questions)

“Class of emission” means a set of characteristics of an emission designated by standard symbols, e.g., the main carrier modulation method, modulating signal, type of information sent, and other applicable signal characteristics. The emission class representing CW telegraphy is:

1. AA1A
2. BJ3E
3. CF2B
4. DG2B

“Class of emission” means a set of characteristics of an emission designated by standard symbols, e.g., the main carrier modulation method, modulating signal, type of information sent, and other applicable signal characteristics. The emission class representing single-sideband (SSB) phone is:

1. AJ3E
2. BA1A
3. CF2B
4. DG2B

“Class of emission” means a set of characteristics of an emission designated by standard symbols, e.g., the main carrier modulation method, modulating signal, type of information sent, and other applicable signal characteristics. The emission class representing an SSTV signal transmitted using SSB phone is:

1. AF3F
2. BJ3E
3. CF2B
4. DF3E

“Class of emission” means a set of characteristics of an emission designated by standard symbols, e.g., the main carrier modulation method, modulating signal, type of information sent, and other applicable signal characteristics. The emission class representing frequency-modulation (FM) phone is:

1. AF3E
2. BF3F
3. CJ3E
4. DF2B

“Class of emission” means a set of characteristics of an emission designated by standard symbols, e.g., the main carrier modulation method, modulating signal, type of information sent, and other applicable signal characteristics. The emission class representing an SSTV signal transmitted using FM phone is:

1. AF3F
2. BF2B
3. CJ3E
4. DF3E

“Class of emission” means a set of characteristics of an emission designated by standard symbols, e.g., the main carrier modulation method, modulating signal, type of information sent, and other applicable signal characteristics. The emission class representing FM ATV (amateur television) is:

1. AF3F
2. BF2B
3. CF3E
4. DJ3E

Out-of-band emission means:

1. Aemission on one or more frequencies immediately outside the necessary bandwidth, resulting from the modulation process, but excluding spurious emission
2. Bemission on one or more frequencies immediately outside the occupied bandwidth, resulting from the modulation process, but excluding spurious emission
3. Cemission on one or more frequencies immediately outside the reference bandwidth, resulting from the modulation process, but excluding spurious emission
4. Demission on one or more frequencies immediately outside the fixed bandwidth, resulting from the modulation process, but excluding spurious emission

In amateur radio communication the three most basic modulations are abbreviated AM, FM and PM. Their Chinese names are:

1. Aamplitude modulation (AM), frequency modulation (FM), phase modulation (PM)
2. Bamplitude modulation (AM), frequency modulation (FM), pulse-width modulation
3. Cfrequency modulation (FM), pulse-code modulation, amplitude modulation (AM)
4. Damplitude modulation (AM), frequency modulation (FM), code modulation (Morse)

Which modulation is widely used for VHF or UHF local contacts?

1. AFM
2. BSSB
3. CPSK
4. DAM

Which modulation is widely used for long-distance and weak-signal VHF or UHF voice contacts?

1. ASSB
2. BAM
3. CFM
4. DPM

Which modulation is widely used for HF voice contacts?

1. ASSB
2. BAM
3. CFM
4. DPM

What is the advantage of SSB compared with FM?

1. Aits transmit bandwidth is narrower than that of FM
2. Bsame-frequency stations do not interfere with each other
3. Cit is immune to atmospheric interference
4. Dit is insensitive to the frequency error of the main carrier

What is the main disadvantage of FM compared with SSB?

1. Ait cannot simultaneously monitor multiple signals
2. Bits ability to resist pulse interference is poor
3. Cit is very sensitive to the frequency error of the main carrier
4. Dit contains a constant carrier component, so transmit-power utilization is inefficient

For SSB contacts on VHF and UHF bands, which sideband is usually selected?

1. Aupper sideband (USB)
2. Blower sideband (LSB)
3. Csuppressed sideband
4. Dvestigial sideband

For voice communication on HF bands of 14 MHz and above, which sideband is usually selected?

1. Aupper sideband (USB)
2. Blower sideband (LSB)
3. Csuppressed sideband
4. Dvestigial sideband

For voice communication on bands of 7 MHz and below, which sideband is usually selected?

1. Alower sideband (LSB)
2. Bupper sideband (USB)
3. Csuppressed sideband
4. Dvestigial sideband

Why do amateur stations use lower sideband for voice below 10.1 MHz but upper sideband above 10.1 MHz?

1. Athis is a contacting convention widely accepted and continuously followed by amateur radio operators of all countries
2. Bfrequencies below 10.1 MHz propagate lower sideband more favorably
3. Cfrequencies above 10.1 MHz propagate upper sideband more favorably
4. Dbecause setting a 10.1 MHz BFO in the receiver can simultaneously receive both upper and lower sidebands

When initiating an SSB call, the frequency separation between you and nearby stations should be at least:

1. A2–3 kHz
2. B150–500 Hz
3. C15–50 Hz
4. Dabout 6 kHz

Which of the following modulation modes can be classified under amplitude modulation (AM)?

1. Asingle-sideband modulation (SSB)
2. Blinear frequency modulation (Chirp)
3. Cdirect-sequence spread spectrum (DSSS)
4. Dphase-shift keying (PSK)

In the amateur radio service there is a communication mode abbreviated CW. Its meaning is:

1. Acontinuous wave (equal-amplitude telegraphy)
2. BMorse coding
3. Camplitude-shift keying
4. Dfrequency-shift keying

Which modulation mode has the narrowest emission bandwidth?

1. ACW
2. BSSB phone
3. CFM phone
4. DATV

Amateur stations generally do not use FM phone for Morse code contacts. This is because:

1. Athe FM phone channel bandwidth exceeds the necessary bandwidth for transmitting Morse code, which does not comply with the requirement in the “Technical Characteristics of Stations” chapter of the Radio Frequency Allocation Regulations of the PRC (《无线电频率划分规定》) to keep bandwidth at the minimum value allowed by the technical state and the nature of the service
2. Bthe FM phone mode cannot transmit Morse code
3. Cthe FM phone mode transmits Morse code unreliably
4. Dthe FM phone mode limits the speed of Morse code transmission

Whether FM or SSB modulation, applying an audio signal 10 times the specified input voltage to the microphone input of the transmitter, the most likely result is:

1. Asignal distortion; a large amount of harmonic and intermodulation products may also increase the emission bandwidth and degrade communication quality
2. Bthe communication distance is effectively extended and the signal sounds fuller
3. Cthe communication distance is effectively extended, only the signal sounds distorted
4. Dthe transmit power exceeds the rated value and the final-stage RF power device of the transmitter will be burned out

Amplitude modulation (AM) is a simple modulation because only the amplitude of the RF carrier varies following the applied modulating signal. The characteristics of AM are: (Choose all that apply.)

1. AAM does not change the frequency of the carrier
2. BThe instantaneous amplitude of an AM signal is proportional to the instantaneous value of the modulating signal
3. CThe instantaneous phase shift of an AM signal is proportional to the instantaneous value of the modulating signal
4. DThe necessary bandwidth of an AM signal is independent of the highest frequency of the modulating signal

An AM signal has not only the lower or upper sideband corresponding to the modulating signal, but may also contain a carrier. These can be subdivided and customized according to communication requirements. If AM signals are subdivided by type, which of the following descriptions is correct? (Choose all that apply.)

1. AAM: ordinary amplitude modulation, containing the lower and upper sidebands, with the carrier not suppressed. CW is a keyed form of AM
2. BDSB-SC: double-sideband suppressed-carrier amplitude modulation, containing only the lower and upper sidebands, often abbreviated as DSB
3. CSSB-SC: single-sideband suppressed-carrier amplitude modulation, only the lower or upper sideband, often abbreviated as SSB, LSB, or USB
4. DVSB: vestigial-sideband amplitude modulation, where the lower or upper sideband is only partially suppressed. Analog ATV sometimes uses this method

A voice signal is modulated by a USB transmitter into an RF signal. From a frequency-domain perspective, this modulation is:

1. Athe spectrum of the voice signal is shifted (translated) to the position of the carrier
2. Bthe relative amplitudes of the spectral components undergo a regular change
3. Cthe spectrum of the voice signal is inverted and shifted to the position of the carrier
4. Da non-linear transformation, thereby producing infinitely many sidebands

A voice signal is modulated by an LSB transmitter into an RF signal. From a frequency-domain perspective, this modulation is:

1. Athe spectrum of the voice signal is inverted and shifted to the position of the carrier
2. Bthe relative amplitudes of the spectral components undergo a regular change
3. Cthe spectrum of the voice signal is shifted (translated) to the position of the carrier
4. Da non-linear transformation, thereby producing infinitely many sidebands

Frequency modulation (FM) is a simple modulation because only the frequency of the RF carrier varies following the applied modulating signal. The characteristics of FM are: (Choose all that apply.)

1. AFM does not change the amplitude of the carrier
2. BThe instantaneous frequency deviation of an FM signal is proportional to the instantaneous value of the modulating signal
3. CThe instantaneous phase shift of an FM signal is proportional to the instantaneous value of the modulating signal
4. DThe necessary bandwidth of an FM signal is independent of the highest frequency of the modulating signal

Which of the following determines the frequency deviation of an FM signal?

1. Athe amplitude of the modulating signal
2. Bthe frequency and amplitude of the modulating signal
3. Cthe frequency of the modulating signal
4. Dthe phase relationship between the modulating signal and the main carrier

Phase modulation (PM) is a simple modulation because only the phase shift of the RF carrier varies following the applied modulating signal. The characteristics of PM are: (Choose all that apply.)

1. APM does not change the amplitude of the carrier
2. BThe instantaneous phase shift of a PM signal is proportional to the instantaneous value of the modulating signal
3. CThe instantaneous frequency deviation of a PM signal is proportional to the instantaneous value of the modulating signal
4. DThe necessary bandwidth of a PM signal is independent of the highest frequency of the modulating signal

For a given FM amateur station, the factor that determines its actual transmitted bandwidth is:

1. Athe higher the highest frequency and the greater the amplitude of the modulating signal to be transmitted, the wider the bandwidth of the modulated signal
2. Bthe higher the highest frequency of the modulating signal to be transmitted, the wider the bandwidth of the modulated signal; it is unrelated to the amplitude of the modulating signal
3. Cthe greater the amplitude of the modulating signal to be transmitted, the wider the bandwidth of the modulated signal; it is unrelated to the highest frequency of the modulating signal
4. Dthe bandwidth of the modulated signal is a nominal value related to the modulation mode; for the amateur service it is 25 kHz or 12.5 kHz

For a given SSB amateur station, the factor that determines its actual transmitted bandwidth is:

1. Athe wider the bandwidth of the modulating signal to be transmitted, the wider the bandwidth of the modulated signal
2. Bthe higher the highest frequency of the modulating signal to be transmitted, the wider the bandwidth of the modulated signal; it is unrelated to the amplitude and bandwidth of the modulating signal
3. Cthe greater the amplitude of the modulating signal to be transmitted, the wider the bandwidth of the modulated signal; it is unrelated to the frequency and bandwidth of the modulating signal
4. Dthe bandwidth of the modulated signal is a nominal value related to the modulation mode; for the amateur service it is 2.7 kHz

In the amateur radio service, the speed of Morse code signals is often measured in WPM; the method of measurement is:

1. Athe number of gap-free ‘dots’ contained per minute divided by 50 gives the WPM number
2. Bthe actual number of English characters keyed per minute is the WPM number
3. Cthe actual number of Chinese characters keyed per minute is the WPM number
4. Dthe number of gap-free ‘dots’ contained per minute divided by 60 gives the WPM number

In the amateur radio service, the signal-timing standard used when calculating the WPM speed of Morse code (with the duration of one ‘dot’ signal as the reference) is: dot signal, dash signal, intra-character dot-dash spacing, inter-character spacing, and inter-word (group) spacing are respectively:

1. A1, 3, 1, 3, 7
2. B1, 3, 1, 3, 5
3. C1, 5, 1, 5, 7
4. D1, 5, 2, 3, 3

The necessary emission bandwidth of a CW signal can be calculated using the formula Bn = B × K. Here, B is the baud rate. If the WPM value of the keyed code is known, then B can be calculated as:

1. AWPM/1.2
2. BWPM+1.2
3. CWPM-1.2
4. DWPM×1.2

The necessary emission bandwidth of a CW signal can be calculated using the formula Bn = B × K. Here, the constant K describes the sideband rolloff characteristic of the CW RF signal when the code symbol flips. The principle for choosing K is:

1. AFor fading channels such as HF, K is taken as 5; for non-fading channels, K as 3 is sufficient
2. BFor non-fading channels, K is taken as 5; for fading channels such as HF, K as 3 is sufficient
3. CFor fading channels such as HF, K is taken as 50 baud; for non-fading channels, K as 300 baud
4. DFor non-fading channels, K is taken as 50 baud; for fading channels such as HF, K as 300 baud

The necessary bandwidth Bn of FM voice depends on the peak frequency deviation D of the FM signal and the highest modulating frequency M. The estimation method is:

1. ABn=2(M+D)
2. BBn=2M+D
3. CBn=M+2D
4. DBn=2(D+M×K)

The modulation methods used for slow-scan television (SSTV) and radio facsimile (FAX) in the amateur bands are both:

1. AFM
2. BAM
3. CPM
4. DCW

What amateur radio slow-scan television transmits is:

1. Aa still image scanned line by line
2. Ba still image scanned in interlaced fashion
3. Ca moving image scanned line by line
4. Da moving image scanned in interlaced fashion

A certain amateur station intends to transmit several circuit diagrams with a resolution of 1024×768 pixels or somewhat higher over a short-wave voice channel. Appropriate modes of communication could be: (Choose all that apply.)

1. Adigital slow-scan television (DSSTV)
2. Bradio facsimile (FAX)
3. Camateur television (ATV)
4. Danalog slow-scan television (SSTV)

When receiving SSTV signals in modes such as Robot, Scottie, Martin, SC2, or PD, we hear a periodic, very brief “click, click” sound; they are:

1. Aline synchronization signals
2. Ba kind of ultra-low-frequency parasitic oscillation
3. Cstandard-frequency and standard-brightness signals
4. DFM and SSB modes beating against each other

SSTV communication provides different transmission modes such as Robot, Scottie, AVT, and Martin. The specific differences are:

1. Aparameters such as pixel resolution, pixel modulation method, line frequency, and frame frequency differ, suited to different picture quality and environmental conditions
2. Bthe occupied bandwidth differs
3. Cthe required receiver sensitivity differs
4. Dthe operational difficulty differs

The method of conducting SSTV contacts using a personal computer (PC) and an ordinary voice transceiver is: (Choose all that apply.)

1. AOn the short-wave bands: FM (audio baseband modulation of the image information) and SSB (frequency translation)
2. BOn the ultra-short-wave bands: FM (audio baseband modulation of the image information) and FM (composite modulation)
3. COn the short-wave bands: FSK (audio baseband modulation of the image information) and SSB (frequency translation)
4. DOn the ultra-short-wave bands: FSK (audio baseband modulation of the image information) and FM (composite modulation)

The baseband signal of slow-scan television (SSTV) is normally generated within the audio range and transmitted by means of single sideband or FM voice. Regarding the SSTV baseband, which of the following descriptions is correct?

1. AFM method: white level is the high frequency 2300 Hz, black level is the low frequency 1500 Hz, sync level is the lowest frequency 1200 Hz
2. BAM method: white level is the high level 87.5%, black level is the low level 30%, sync level is the lowest level 25%
3. CAM method: white level is the low level 75%, black level is the high level 75%, sync level is the highest level 100%
4. DAM method: white level is the low frequency 1200 Hz, black level is the high frequency 2000 Hz, sync level is the highest frequency 2300 Hz

If the received SSTV or ATV image shows thick horizontal black stripes and the upper and lower half-frames are misaligned, it is because:

1. Aboth sides’ line frequency and frame frequency are consistent, but the initial moment of frame scanning is not synchronized
2. Bboth sides’ scanning line frequencies are inconsistent
3. Cboth sides’ equipment is not accurately tuned to the same frequency
4. Dboth sides’ equipment has not correctly set the modulation polarity

If the received SSTV or ATV image is tilted left-right, appearing as a parallelogram or slanted thick-stripe pattern, it is because:

1. Aboth sides’ scanning line frequencies are inconsistent
2. Bboth sides’ line frequency and frame frequency are consistent, but the initial moment of frame scanning is not synchronized
3. Cboth sides’ equipment is not accurately tuned to the same frequency
4. Dboth sides’ equipment has not correctly set the modulation polarity

Why can’t regular ATV communication be conducted in amateur bands below 1.2 GHz?

1. AATV communication requires a bandwidth of more than 5 MHz, which the lower amateur bands cannot accommodate
2. BMost voice communication is concentrated in the lower bands, which can cause severe interference to ATV communication
3. CMost voice communication is concentrated in the lower bands, and since ATV picture transmission usually lasts a long time, one should proactively yield
4. DThe higher the frequency, the more stable the quality of ATV transmission

Sometimes, amateur radio operators use FM instead of the classic VSB method commonly used in TV broadcasting to transmit analog ATV signals. The advantage of doing this is:

1. AThe ATV signal’s transmit power is relatively small, and FM demodulation can better remove external amplitude-modulation noise superimposed on the signal
2. BIf the instantaneous frequency deviation is reduced, the necessary emission bandwidth of FM would be narrower than that of VSB
3. CThe sensitivity of FM receivers is an order of magnitude (at least 10 dB) higher than that of AM receivers
4. DIt is convenient to be compatible with equipment operating in FM voice mode (e.g., handheld transceivers)

Sometimes, amateur stations use VSB to transmit analog ATV signals. Although this method belongs to AM, it sends only one complete sideband plus a small part of the other sideband near the carrier. When transmitting analog video, the advantages of VSB are: (Choose all that apply.)

1. Aa narrower emission bandwidth than AM
2. Bit ensures the fidelity of low-frequency components in the video signal
3. Cit ensures the negative-polarity transmission of black and white levels
4. Dit saves more transmit power than single sideband