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ARRL Ham Radio License - Technician Class > Signals and Emissions > Flashcards

Signals and Emissions Flashcards

1
Q

Which of the following is a form of amplitude modulation?
A. Spread spectrum
B. Packet radio
C. Single sideband
D. Phase shift keying (PSK)

A

C. Single sideband

Single Sidebandis commonly used for voice on HF. It is amplitude modulation (AM) with the carrier and one sideband removed. This halves the required bandwidth and saves the large amount of power that would otherwise go into the carrier. This makes SSB much more effective than conventional AM over long distances on crowded bands with limited transmitter power.

Spread-spectrumis not itself a form of modulation, but a family of techniques that spread a (usually already modulated) signal over a wide range of frequencies to reduce interference, tolerate multipath, avoid detection, etc.

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2
Q

What type of modulation is commonly used for VHF packet radio transmissions?
A. FM or PM
B. SSB
C. AM
D. PSK

A

A. FM or PM

Since packet radio benefits from good bandwidth and minimal audio amplitude variations, both of which are advantages of FM; and because FM is an allowed modulation method on VHF, FM is the most commonly used modulation for packet.

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3
Q

Which type of voice mode is often used for long-distance (weak signal) contacts on the VHF and UHF bands?
A. FM
B. DRM
C. SSB
D. PM

A

C. SSB

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4
Q

Which type of modulation is commonly used for VHF and UHF voice repeaters?
A. AM
B. SSB
C. PSK
D. FM or PM

A

D. FM or PM

FM (Frequency Modulation) is the same modulation used by the FM radio in your car, which makes it easier to remember. Note that regular FM radio broadcast stations (music, talk radio, etc) use what is commonly known as Wide FM with a 200 kHz bandwidth, whereas ham radio generally uses Narrow FM which uses about 15-20kHz.

Strictly speaking, what hams call FM is actually PM (Phase Modulation), which is very closely related to FM, differing only in their audio frequency responses. PM is FM with +6dB/octave pre-emphasis and -6 dB/octave de-emphasis.

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5
Q

Which of the following types of signal has the narrowest bandwidth?
A. FM voice
B. SSB voice
C. CW
D. Slow-scan TV

A

C. CW

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6
Q

Which sideband is normally used for 10 meter HF, VHF, and UHF single-sideband communications?
A. Upper sideband
B. Lower sideband
C. Suppressed sideband
D. Inverted sideband

A

A. Upper sideband

By convention, Upper Sideband (USB) is used for SSB on 10MHz HF and up – including VHF and UHF bands. You will need to just remember upper sideband for the upper-frequency bands, 10MHz and up.

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7
Q

What is a characteristic of single sideband (SSB) compared to FM?
A. SSB signals are easier to tune in correctly
B. SSB signals are less susceptible to interference
C. SSB signals have narrower bandwidth
D. All these choices are correct

A

C. SSB signals have narrower bandwidth

AM has two mirror-image sidebands, upper and lower, and a carrier that contains a lot of power but no information. Single sideband (SSB) omits the carrier and one sideband, putting all of its power into the remaining (single) sideband. This halves the signal bandwidth and makes much more efficient use of transmitted power.

The narrower bandwidth does make SSB less susceptible to interference in the sense that it’s a smaller target. But it is still susceptible to interference that lands within its smaller bandwidth. What’s more important is that its narrower bandwidth means it causes less interference tootherusers of the band.

SSB isharderto tune than either AM or FM, whose carriers provide a frequency “reference” to the receiver. Without a carrier to go on, the SSB receiver must provide an accurate one of its own by careful local tuning.

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8
Q

What is the approximate bandwidth of a typical single sideband (SSB) voice signal?
A. 1 kHz
B. 3 kHz
C. 6 kHz
D. 15 kHz

A

B. 3 kHz

Single Sidebandis a modified form of Amplitude Modulation (AM). Because AM has two mirror-image sidebands, it normally uses twice the bandwidth of the modulating signal. Because single sideband only transmits one sideband, its radio frequency bandwidth is equal to the bandwidth of the modulating signal. SSB also omits the AM carrier, but it does not consume any radio bandwidth.

A traditional communications-grade voice signal extends from about 300 to 3300 Hz, with newer transceivers using digital signal processing (DSP) extending the low end to about 100 Hz to improve fidelity. So the radio bandwidth of a SSB signal is very approximately 3 kHz.

As a memory aid, note that SSB has 3 letters, which is the same number of kHz as the bandwidth, 3 kHz.

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9
Q

What is the approximate bandwidth of a VHF repeater FM voice signal?
A. Less than 500 Hz
B. About 150 kHz
C. Between 10 and 15 kHz
D. Between 50 and 125 kHz

A

C. Between 10 and 15 kHz

According to Carson’s Rule, the approximate bandwidth of an FM signal is equal to twice the sum of the highest modulating frequency and the deviation. For standard ham FM, this is 2 * (3 kHz + 5 kHz) = 16 kHz. If you transmit on 146.520MHz and listen on 146.525MHz you will likely still hear the signal. If you can’t (or barely can) then the bandwidth is closer to 5kHz – (standard for FRS radios, for example). The further away you get the wider the bandwidth would need to be for you to still be able to hear it.

Remember that if the bandwidth is 5kHz you will only hear them at the transmit frequency +/- 2.5kHz, because the transmit frequency is the middle so half will be above and half below. Most amateur FM uses +/- 5 kHz deviation but some support “half deviation” mode which uses +/- 2.5 kHz.

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10
Q

What is the approximate bandwidth of AM fast-scan TV transmissions?
A. More than 10 MHz
B. About 6 MHz
C. About 3 MHz
D. About 1 MHz

A

B. About 6 MHz

Analog fast-scan TV transmissions use a lot of bandwidth compared to voice and other modes. When US amateurs use the (now obsolete) US NTSC analog TV broadcast standard, the bandwidth is the same as a US TV channel: 6 MHz.

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11
Q

What is the approximate bandwidth required to transmit a CW signal?
A. 2.4 kHz
B. 150 Hz
C. 1000 Hz
D. 15 kHz

A

B. 150 Hz

CW uses the least bandwidth of all commonly used modes; all you really need to get across clearly is a single tone so that the receiving station can hear when it is “on” or “off”.

A good rule of thumb for CW (Continuous Wave, Morse Code) is that when it asks about bandwidth it’s probably the smallest value listed. There are a very few digital modes which use less bandwidth than CW but none which make that comparison which are in this question pool.

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12
Q

Which of the following is a disadvantage of FM compared with single sideband?
A. Voice quality is poorer
B. Only one signal can be received at a time
C. FM signals are harder to tune
D. All these choices are correct

A

B. Only one signal can be received at a time

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13
Q

What telemetry information is typically transmitted by satellite beacons?
A. The signal strength of received signals
B. Time of day accurate to plus or minus 1/10 second
C. Health and status of the satellite
D. All these choices are correct

A

C. Health and status of the satellite

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14
Q

What is the impact of using excessive effective radiated power on a satellite uplink?
A. Possibility of commanding the satellite to an improper mode
B. Blocking access by other users
C. Overloading the satellite batteries
D. Possibility of rebooting the satellite control computer

A

B. Blocking access by other users

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15
Q

Which of the following are provided by satellite tracking programs?
A. Maps showing the real-time position of the satellite track over Earth
B. The time, azimuth, and elevation of the start, maximum altitude, and end of a pass
C. The apparent frequency of the satellite transmission, including effects of Doppler shift
D. All these choices are correct

A

D. All these choices are correct

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16
Q

What mode of transmission is commonly used by amateur radio satellites?
A. SSB
B. FM
C. CW/data
D. All these choices are correct

A

D. All these choices are correct

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17
Q

What is a satellite beacon?
A. The primary transmit antenna on the satellite
B. An indicator light that shows where to point your antenna
C. A reflective surface on the satellite
D. A transmission from a satellite that contains status information

A

D. A transmission from a satellite that contains status information

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18
Q

Which of the following are inputs to a satellite tracking program?
A. The satellite transmitted power
B. The Keplerian elements
C. The last observed time of zero Doppler shift
D. All these choices are correct

A

B. The Keplerian elements

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19
Q

What is Doppler shift in reference to satellite communications?
A. A change in the satellite orbit
B. A mode where the satellite receives signals on one band and transmits on another
C. An observed change in signal frequency caused by relative motion between the satellite and Earth station
D. A special digital communications mode for some satellites

A

C. An observed change in signal frequency caused by relative motion between the satellite and Earth station

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20
Q

What is meant by the statement that a satellite is operating in U/V mode?
A. The satellite uplink is in the 15 meter band and the downlink is in the 10 meter band
B. The satellite uplink is in the 70 centimeter band and the downlink is in the 2 meter band
C. The satellite operates using ultraviolet frequencies
D. The satellite frequencies are usually variable

A

B. The satellite uplink is in the 70 centimeter band and the downlink is in the 2 meter band

21
Q

What causes spin fading of satellite signals?
A. Circular polarized noise interference radiated from the sun
B. Rotation of the satellite and its antennas
C. Doppler shift of the received signal
D. Interfering signals within the satellite uplink band

A

B. Rotation of the satellite and its antennas

22
Q

What is a LEO satellite?
A. A sun synchronous satellite
B. A highly elliptical orbit satellite
C. A satellite in low energy operation mode
D. A satellite in low earth orbit

A

D. A satellite in low earth orbit

23
Q

Who may receive telemetry from a space station?
A. Anyone
B. A licensed radio amateur with a transmitter equipped for interrogating the satellite
C. A licensed radio amateur who has been certified by the protocol developer
D. A licensed radio amateur who has registered for an access code from AMSAT

A

A. Anyone

Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment (telecommunication) for monitoring.

24
Q

Which of the following is a way to determine whether your satellite uplink power is neither too low nor too high?
A. Check your signal strength report in the telemetry data
B. Listen for distortion on your downlink signal
C. Your signal strength on the downlink should be about the same as the beacon
D. All these choices are correct

A

C. Your signal strength on the downlink should be about the same as the beacon

25
Q

Which of the following methods is used to locate sources of noise interference or jamming?
A. Echolocation
B. Doppler radar
C. Radio direction finding
D. Phase locking

A

C. Radio direction finding

When there is radio interference, whether intentional or unintentional, you can use radio direction finding to track down the interfering noise source. This can be a directional antenna or some other means of determining where the offender is located. After you have a direction from two locations you can pinpoint where to go to find your culprit.

26
Q

Which of these items would be useful for a hidden transmitter hunt?
A. Calibrated SWR meter
B. A directional antenna
C. A calibrated noise bridge
D. All these choices are correct

A

B. A directional antenna

27
Q

What operating activity involves contacting as many stations as possible during a specified period?
A. Simulated emergency exercises
B. Net operations
C. Public service events
D. Contesting

A

D. Contesting

28
Q

Which of the following is good procedure when contacting another station in a contest?
A. Sign only the last two letters of your call if there are many other stations calling
B. Contact the station twice to be sure that you are in his log
C. Send only the minimum information needed for proper identification and the contest exchange
D. All these choices are correct

A

C. Send only the minimum information needed for proper identification and the contest exchange

29
Q

What is a grid locator?
A. A letter-number designator assigned to a geographic location
B. A letter-number designator assigned to an azimuth and elevation
C. An instrument for neutralizing a final amplifier
D. An instrument for radio direction finding

A

A. A letter-number designator assigned to a geographic location

30
Q

How is over the air access to IRLP nodes accomplished?
A. By obtaining a password that is sent via voice to the node
B. By using DTMF signals
C. By entering the proper internet password
D. By using CTCSS tone codes

A

B. By using DTMF signals

The Internet Radio Linking Project, also called IRLP links amateur radio stations around the world by using Voice over IP (VoIP).

Dual-tone multi-frequency signaling (DTMF) is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and switching centers.

31
Q

What is Voice Over Internet Protocol (VoIP)?
A. A set of rules specifying how to identify your station when linked over the internet to another station
B. A technique employed to “spot” DX stations via the internet
C. A technique for measuring the modulation quality of a transmitter using remote sites monitored via the internet
D. A method of delivering voice communications over the internet using digital techniques

A

D. A method of delivering voice communications over the internet using digital techniques

32
Q

What is the Internet Radio Linking Project (IRLP)?
A. A technique to connect amateur radio systems, such as repeaters, via the internet using Voice Over Internet Protocol (VoIP)
B. A system for providing access to websites via amateur radio
C. A system for informing amateurs in real time of the frequency of active DX stations
D. A technique for measuring signal strength of an amateur transmitter via the internet

A

A. A technique to connect amateur radio systems, such as repeaters, via the internet using Voice Over Internet Protocol (VoIP)

IRLPis one of several projects used for linking repeaters and other systems across the internet.

Amateurs use DTMF tones (phone keypad) on a radio to send control codes to the repeater to link or unlink with another repeater or node.

Similar technologies includeEchoLink,AllStar, and Icom’sD-Starnetwork.

33
Q

Which of the following protocols enables an amateur station to transmit through a repeater without using a radio to initiate the transmission?
A. IRLP
B. D-STAR
C. DMR
D. EchoLink

A

D. EchoLink

Memory Aid: Echo = Repeat(er)

Technically there are ways with IRLP, D-Star, and DMR to access a repeater without using a radio, but they are generally discouraged by the maintainers of the technology.

By contrast, EchoLink is designed so that you can use the EchoLink application and a verified account to access any EchoLink-enabled repeater.

34
Q

What is required before using the EchoLink system?
A. Complete the required EchoLink training
B. Purchase a license to use the EchoLink software
C. Register your call sign and provide proof of license
D. All these choices are correct

A

C. Register your call sign and provide proof of license

Echolinkis a system of Internet-connected repeaters that can be connected to with client software and used to receive and transmit on amateur radio bands (VHF and UHF). It is essentially a method of remotely controlling a station, so when using ityou are the control operator of whichever station you are using.

35
Q

What is an amateur radio station that connects other amateur stations to the internet?
A. A gateway
B. A repeater
C. A digipeater
D. A beacon

A

A. A gateway

In computer terms a gateway is the name of a device that connects two different networks together; a router is a type of gateway. Thus, a station that connects a packet radio network to the Internet is also a gateway.

36
Q

Which of the following is a digital communications mode?
A. Packet radio
B. IEEE 802.11
C. FT8
D. All these choices are correct

A

D. All these choices are correct

Digital communications methods are methods that send digital information (encoded in bits, 0 or 1) instead of sending an analog signal, such as voice or video.

37
Q

What is a “talkgroup” on a DMR repeater?
A. A group of operators sharing common interests
B. A way for groups of users to share a channel at different times without hearing other users on the channel
C. A protocol that increases the signal-to-noise ratio when multiple repeaters are linked together
D. A net that meets at a specified time

A

B. A way for groups of users to share a channel at different times without hearing other users on the channel

Memory aid: a ‘talk group’ allows agrouptotalktogether (share)

A talk group on a DMR digital repeater is a way for groups of users to share a channel at different times without being heard by other users on the channel. This is accomplished by ID codes transmitted by the users. Users in a particular group will program their radios with the ID code for their group. Users’ radios not programmed to their group’s code will remain silent, even while on the same channel.

38
Q

What kind of data can be transmitted by APRS?
A. GPS position data
B. Text messages
C. Weather data
D. All these choices are correct

A

D. All these choices are correct

Automatic Packet Reporting System (APRS) is an amateur radio-based system for real time digital communications of information of immediate value in the local area.

39
Q

What type of transmission is indicated by the term “NTSC?”
A. A Normal Transmission mode in Static Circuit
B. A special mode for satellite uplink
C. An analog fast-scan color TV signal
D. A frame compression scheme for TV signals

A

C. An analog fast-scan color TV signal

NTSC is the name of the standard used to encode colors in an analog fast scan color TV signal.

If you ask a broadcast engineer,NTSCstands forNever The Same Color, because his job is to keep all the cameras looking the same. Now that TV is in the Digital Age the only people you see using the NTSC broadcast standard are Amateur Radio Operators.

Actually, NTSC stands for National Television Systems Committee. They created the rules that governed what the broadcast signal would be electronically so every TV would be able to display the correct picture

40
Q

Which of the following is an application of APRS?
A. Providing real-time tactical digital communications in conjunction with a map showing the locations of stations
B. Showing automatically the number of packets transmitted via PACTOR during a specific time interval
C. Providing voice over internet connection between repeaters
D. Providing information on the number of stations signed into a repeater

A

A. Providing real-time tactical digital communications in conjunction with a map showing the locations of stations

Amateur Packet Reporting System (APRS) is a digital communication system utilized by amateur radio operators to exchange messages and track locations utilizing GPS.

41
Q

What does the abbreviation “PSK” mean?
A. Pulse Shift Keying
B. Phase Shift Keying
C. Packet Short Keying
D. Phased Slide Keying

A

B. Phase Shift Keying

Phase-shift keying (PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency carrier wave. The modulation is accomplished by varying the sine and cosine inputs at a precise time. It is widely used for wireless LANs, RFID and Bluetooth communication.

42
Q

Which of the following describes DMR?
A. A technique for time-multiplexing two digital voice signals on a single 12.5 kHz repeater channel
B. An automatic position tracking mode for FM mobiles communicating through repeaters
C. An automatic computer logging technique for hands-off logging when communicating while operating a vehicle
D. A digital technique for transmitting on two repeater inputs simultaneously for automatic error correction

A

A. A technique for time-multiplexing two digital voice signals on a single 12.5 kHz repeater channel

DMR (DigitalMobileRadio) is one of several digital modes. It’s the only one that uses time-multiplexing to allow two digital voice signals to be repeated through the same repeater, using the same 12.5 kHz repeater channel.

It’s not a position tracking system.

It’s not a logging technique.

The third distractor is tempting, because it talks about two simultaneous repeater inputs, but the part about time-multiplexing is unique to DMR, so the best answer.

43
Q

Which of the following is included in packet radio transmissions?
A. A check sum that permits error detection
B. A header that contains the call sign of the station to which the information is being sent
C. Automatic repeat request in case of error
D. All these choices are correct

A

D. All these choices are correct

A checksum is an error detection method used by many data transmission types including packet radio. Basically all bytes in the message are added (summed) up and sent as a “checksum”. The receiving station repeates this process and “checks” the result against the checksum it received from the sending station.

If the checksum fails (the sums don’t match) then an automatic repeat request is sent.

Since packet radio is a form of amateur radio communications the destination station is generally identified at least by call sign, so that information is often included in the header as well.

44
Q

What is CW?
A. A type of electromagnetic propagation
B. A digital mode used primarily on 2 meter FM
C. A technique for coil winding
D. Another name for a Morse code transmission

A

D. Another name for a Morse code transmission

45
Q

Which of the following operating activities is supported by digital mode software in the WSJT-X software suite?
A. Earth-Moon-Earth
B. Weak signal propagation beacons
C. Meteor scatter
D. All these choices are correct

A

D. All these choices are correct

WSJT [WeakSignalJT(after the program’s initial author, Joseph Hooton Taylor Jr.)] is software that facilitates short, quick digital transmissions and is very useful for weak signals.

As such, it’s great for moonbounce (Earth-Moon-Earth), weak signal beacons, and meteor scatter, all of which result in very little of the transmitted signal reaching anyone’s receiver.

46
Q

What is an ARQ transmission system?
A. A special transmission format limited to video signals
B. A system used to encrypt command signals to an amateur radio satellite
C. An error correction method in which the receiving station detects errors and sends a request for retransmission
D. A method of compressing data using autonomous reiterative Q codes prior to final encoding

A

C. An error correction method in which the receiving station detects errors and sends a request for retransmission

ARQstands for Automatic Repeat reQuest

When the receiving station detects an error, itautomaticallysends arepeat requestto the sending station.

It has nothing to do with encryption (which would be illegal except for sending commands to a satellite), or video signals, or data compression. Indeed, it takes a long time to have the receiving station send a repeat request and to then re-transmit the message, or portion of the message.

47
Q

Which of the following best describes an amateur radio mesh network?
A. An amateur-radio based data network using commercial Wi-Fi equipment with modified firmware
B. A wide-bandwidth digital voice mode employing DMR protocols
C. A satellite communications network using modified commercial satellite TV hardware
D. An internet linking protocol used to network repeaters

A

A. An amateur-radio based data network using commercial Wi-Fi equipment with modified firmware

WiFiis the only protocol listed in this question that takes advantage of meshing. “Mesh Networking” is defined by Wikipedia as “a local network topology in which the infrastructure nodes connect directly, dynamically and non-hierarchically to as many other nodes as possible”.

Repeaters may be networked but are often done hierarchically (e.g. a main node and child nodes). DMR is not mesh, and satellite communications are not as well.

48
Q

What is FT8?
A. A wideband FM voice mode
B. A digital mode capable of low signal-to-noise operation
C. An eight channel multiplex mode for FM repeaters
D. A digital slow-scan TV mode with forward error correction and automatic color compensation

A

B. A digital mode capable of low signal-to-noise operation

FT8 is a relatively new digital mode which became popular in 2017. FT8 stands forFranke-Taylor 8-Frequency-Shift Keying modulation. FT8 was created by Joe Taylor, K1JT, and Steve Franke, K9AN.

It very quickly largely replaced JT65 because it’s much faster. FT8 is usually used on HF bands and it can achieve very long distances because it isextremelytolerant of noise and interference. It requires that both transmitter and receivers synchronize their computer time with the same time source (which is easy with the internet).

When you transmit, you transmit for 15 seconds and send only a very short (75 bit) message with a 12 bit checksum. Hint: Remember FT as fifteen.

ARRL Ham Radio License - Technician Class (9 decks)

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