T8 Signals and Emissions

C. Single sideband

Single sideband is a form of amplitude modulation: it starts as an AM signal, then the carrier and one sideband are removed, leaving a single sideband that carries the voice information in about half the bandwidth of AM.

• A. Spread spectrum spreads a signal over a wide bandwidth with techniques such as frequency hopping; it is not a form of amplitude modulation.
• B. Packet radio is a digital data protocol; on VHF it is usually sent as tones over an FM signal.
• D. Phase shift keying sends data by shifting the phase of the carrier, which is a form of phase modulation, not amplitude modulation.

A. FM or PM

VHF packet radio is usually sent through ordinary FM transceivers, with the data carried as audio tones or direct frequency shifts on an FM (or PM) signal.

• B. SSB is used for HF digital modes and weak-signal work, not for typical VHF packet.
• C. AM is not used for VHF packet radio.
• D. PSK is a separate digital modulation, used for example by PSK31 on HF; VHF packet normally uses FM.

C. SSB

SSB concentrates the transmitter's power in a narrow signal about 3 kHz wide, so it remains readable at much weaker signal levels than FM. VHF and UHF operators use SSB (and CW) for long-distance contacts, while FM is used mostly for local and repeater work.

• A. FM needs a fairly strong signal to sound clear, so it is used mostly for local and repeater contacts.
• B. DRM (Digital Radio Mondiale) is a digital broadcasting standard, not an amateur weak-signal voice mode.
• D. PM behaves much like FM on the air, so it has the same need for strong signals.

D. FM or PM

VHF and UHF voice repeaters use FM or PM (phase modulation, which an FM receiver can receive). FM gives clear audio with adequate signal strength, rejects amplitude noise, and is easy to tune on fixed channels.

• A. AM is not the standard mode on amateur voice repeaters.
• B. SSB is used for weak-signal and long-distance work, not for repeaters.
• C. PSK is a digital data mode, not the voice modulation used by repeaters.

C. CW

A CW signal is a carrier switched on and off, so it occupies only about 150 Hz, far less than any voice or image mode.

• A. FM voice is one of the widest common amateur modes, about 10 to 15 kHz.
• B. SSB voice is about 3 kHz wide, many times wider than CW.
• D. Slow-scan TV is sent as audio tones through an SSB voice channel, so it occupies about the same 3 kHz as SSB voice.

A. Upper sideband

By convention, amateurs use upper sideband on 10 meters and on the VHF and UHF bands, as well as on 20 meters and the other HF bands above it. Lower sideband is normally used on 160, 80 and 40 meters.

• B. Lower sideband is normally used on 160, 80 and 40 meters, not on 10 meters and higher.
• C. In SSB the suppressed sideband is the one that is removed; it is not a sideband used for communication.
• D. Inverted sideband is not a standard operating choice; amateurs choose between upper and lower sideband.

C. SSB signals have narrower bandwidth

An SSB voice signal is about 3 kHz wide, while FM voice is about 10 to 15 kHz, so SSB uses much less spectrum and concentrates its power in a narrower signal.

• A. SSB is harder to tune: it must be tuned precisely or voices sound high- or low-pitched, while FM signals are easy to tune in.
• B. FM is less affected by noise and interference because the receiver ignores amplitude changes; SSB is more susceptible.
• D. SWR depends on the antenna system, not the mode, so SSB and FM are affected equally.

B. 3 kHz

An SSB voice signal carries one sideband of speech audio, which extends to about 3 kHz, so the signal occupies about 3 kHz of spectrum.

• A. 1 kHz is too narrow for the range of audio frequencies in speech; an SSB voice signal needs about three times that width.
• C. 6 kHz is the width of a double-sideband AM voice signal, which has two sidebands of about 3 kHz each.
• D. 15 kHz is in the range of an FM voice signal, not SSB.

C. Between 10 and 15 kHz

An FM voice signal on a VHF repeater occupies between 10 and 15 kHz: the carrier frequency swings up to about 5 kHz each side of center with the speech, and the voice audio adds sidebands beyond that swing.

• A. Less than 500 Hz is the width of CW and narrow digital signals, far too narrow for FM voice.
• B. About 150 kHz is on the scale of FM broadcast stations, which use much wider deviation than amateur voice FM.
• D. 50 to 125 kHz is far wider than amateur FM voice needs and would span several repeater channels.

B. About 6 MHz

Fast-scan TV carries full-motion video, which needs far more bandwidth than voice. An AM fast-scan TV signal occupies about 6 MHz, the same as a standard analog broadcast TV channel, which is why amateur fast-scan TV is found on the 70 cm and higher bands.

• A. More than 10 MHz is wider than an analog fast-scan TV signal needs.
• C. About 3 MHz is too narrow for a standard analog fast-scan TV picture.
• D. About 1 MHz is far too narrow for full-motion analog TV.

B. 150 Hz

A CW signal is a carrier keyed on and off at Morse code speeds, and a properly keyed signal at normal speeds occupies only about 150 Hz. This is why many CW signals fit in the space of one voice signal.

• A. 2.4 kHz is typical of an SSB voice signal, not CW.
• C. 1000 Hz is several times wider than a properly keyed CW signal needs.
• D. 15 kHz is in the range of an FM voice signal.

B. Only one signal can be received at a time

FM receivers show the capture effect: the strongest signal on the channel takes over and weaker ones are suppressed, so only one signal can be heard at a time. With SSB, several overlapping signals can be heard at once.

• A. FM voice quality is generally better than SSB when signals are strong enough.
• C. FM signals are easier to tune; small tuning errors barely change the audio, unlike SSB.
• D. SWR depends on the antenna and feed line, not on the modulation, so FM is not more susceptible.

C. Health and status of the satellite

Satellite beacons commonly send telemetry on the satellite's health and status, such as battery voltage, solar panel currents and temperatures. Ground stations decode it to monitor the spacecraft.

• A. Beacon telemetry reports on the satellite's own systems; it is not a report of the strength of the signals users send to it.
• B. Precise time signals come from time stations such as WWV, not from amateur satellite beacons.
• D. Health and status data is the typical beacon telemetry, so not all of these choices are correct.

B. Blocking access by other users

A satellite transponder shares its limited power among all the signals it relays. An uplink signal stronger than needed takes a larger share of that power, or captures a single-channel FM satellite, which blocks or weakens other users.

• A. Commanding a satellite is done by a designated telecommand station that may use special codes (47 CFR 97.211); an ordinary uplink signal, however strong, does not change the satellite's mode.
• C. The satellite's batteries are charged by its solar panels; a strong uplink signal does not overload them.
• D. A strong uplink signal is relayed or blocks other users; it does not reboot the satellite's control computer.

D. All these choices are correct

Satellite tracking programs use orbital data to show where a satellite is, when it will pass over your location and where to point your antenna, and what frequency to tune to allow for Doppler shift.

• A. Real-time maps of the satellite's track over Earth are provided by tracking programs, but they are only part of the answer.
• B. Pass predictions with the time, azimuth and elevation at the start, highest point and end of a pass are provided, but they are only part of the answer.
• C. Frequencies corrected for Doppler shift are provided, but they are only part of the answer.

D. All these choices are correct

Amateur satellites use a range of modes: linear transponders relay SSB and CW signals, FM satellites work as single-channel repeaters for voice, and many satellites send CW or data telemetry or relay digital packets.

• A. SSB is common on satellites with linear transponders, but it is only part of the answer.
• B. FM is common on single-channel repeater satellites, but it is only part of the answer.
• C. CW and data are common for telemetry and digital contacts, but they are only part of the answer.

D. A transmission from a satellite that contains status information

A satellite beacon is a transmission from the satellite that carries status information (telemetry). Operators also use it to find the satellite's signal and judge their own downlink reception.

• A. The beacon is a signal, not the antenna that sends it.
• B. A beacon is a radio transmission, not a light; a tracking program tells you where to point your antenna.
• C. A beacon is a transmitted signal, not a reflective surface.

B. The Keplerian elements

Keplerian elements are the set of numbers that describe a satellite's orbit, such as its inclination, eccentricity and position at a reference time (the epoch). Tracking programs use current elements to predict where the satellite will be.

• A. The satellite's transmitted power has no bearing on where it is, so it is not an input for predicting its position.
• C. Tracking programs calculate Doppler shift from the orbit; the time of zero Doppler shift is a result, not an input.
• D. Only the Keplerian elements are a tracking program input, so not all of these choices are correct.

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

Doppler shift is the observed change in frequency caused by relative motion between the transmitter and the receiver. As a satellite approaches, its signals arrive higher in frequency, and as it moves away they arrive lower, so you retune during a pass.

• A. A change in the satellite's orbit is an orbital change, not Doppler shift.
• B. Receiving on one band and transmitting on another describes a satellite's operating mode, such as U/V.
• D. Doppler shift is a physical effect of motion, not a digital communications mode.

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

Satellite modes name the uplink band first and the downlink band second, using U for UHF and V for VHF. In U/V mode you transmit to the satellite on 70 cm (around 435 MHz) and receive its downlink on 2 meters (around 145 MHz).

• A. A 15-meter uplink with a 10-meter downlink uses HF bands; U and V stand for UHF and VHF.
• C. U and V stand for UHF and VHF, not ultraviolet; satellites communicate by radio.
• D. The letters identify the uplink and downlink bands; they do not mean the frequencies are variable.

B. Rotation of the satellite and its antennas

Many satellites spin or tumble in orbit. As the satellite's antennas rotate, the strength and polarization of the signal reaching you change, causing regular, repeating fades called spin fading.

• A. The sun is a source of radio noise, but it does not cause the regular, repeating fades of spin fading.
• C. Doppler shift changes the received frequency; it does not cause regular fading.
• D. Interfering signals in the uplink band cause interference, not the regular fading produced by the satellite's rotation.

D. Low Earth Orbit, which has a period of around 100 minutes

LEO means Low Earth Orbit. Satellites in low Earth orbit circle a few hundred to about 1,000 km above the Earth and complete each orbit in roughly 90 to 105 minutes, so they move quickly across the sky and are in view only briefly on each pass.

• A. LEO does not mean Low Energy Orbit, and the term says nothing about battery power.
• B. LEO does not mean Low Elevation Orbit; a satellite in low orbit can pass high overhead.
• C. LEO does not mean Low Equilibrium Orbit; the term describes the orbit's low altitude.

A. Anyone

Anyone may receive amateur transmissions, including satellite telemetry; listening requires no license. Part 97 lets only telecommand stations use codes that obscure the meaning of their messages to a space station (47 CFR 97.211(b)), and satellite builders typically publish their telemetry formats so listeners can decode them.

• B. Telemetry is not limited to the satellite's control operator; anyone may receive it.
• C. Amateur telemetry is not restricted by an encryption key; only telecommand messages sent to the satellite may be coded to obscure their meaning.
• D. No encryption key is needed to receive amateur satellite telemetry, from AMSAT or anyone else.

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

On a linear transponder, the satellite's beacon gives a reference level. Set your uplink power so your signal on the downlink is about as strong as the beacon: weaker and you are hard to copy, stronger and you take transponder power away from other users.

• A. Telemetry reports the satellite's own condition, not the strength of individual users' signals.
• B. Distortion on your downlink can have many causes and does not tell you whether your power is too high or too low; the beacon gives a steady reference.
• D. Other users' signals vary widely in strength, so they are not a reliable reference; the beacon is.

C. Radio direction finding

Radio direction finding uses directional antennas, often with bearings taken from several locations, to determine where a signal is coming from. It is used to track down sources of noise, interference and jamming.

• A. Echolocation finds objects by sending out sound and listening for echoes, as bats do; it does not locate radio signals.
• B. Doppler radar transmits radio signals and measures their reflections to find the speed of objects such as rain; it does not locate a transmitter or noise source.
• D. Phase locking keeps an oscillator synchronized to a reference signal, as in a phase-locked loop; it is not a way to find a signal's source.

B. A directional antenna

In a hidden transmitter hunt (fox hunt), a directional antenna such as a small handheld Yagi shows which way the signal is strongest, giving a bearing toward the transmitter.

• A. An SWR meter measures the match between a feed line and its antenna; it cannot show the direction of a signal's source.
• C. A directional wattmeter measures forward and reflected power in your own feed line; it does not show the direction of a received signal.
• D. Only the directional antenna helps find the transmitter, so not all of these choices are correct.

D. Contesting

In a contest, stations try to contact as many other stations as possible during a set period, such as a weekend or a few hours, exchanging specified information with each one.

• A. Simulated emergency exercises practice emergency communications; the goal is handling messages, not counting contacts.
• B. Net operations are organized on-air meetings run by a net control station, not a race to make contacts.
• C. Hidden transmitter hunts involve locating a hidden transmitter, not making many contacts.

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

Contest contacts are short and efficient: send your full call sign and the required contest exchange, and nothing more. This makes good use of everyone's time while still identifying your station properly.

• A. A partial call sign is not proper identification; 47 CFR 97.119(a) requires stations to transmit their assigned call sign, and contest logs need complete calls.
• B. Working the same station twice wastes time for both stations, and duplicate contacts usually earn no points.
• D. Adding phrases such as "Please copy" wastes time; contest exchanges contain only the needed information.

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

A grid locator (Maidenhead locator) is a letter-number code, such as FN31, that identifies a rectangular area of the Earth's surface by latitude and longitude. Operators exchange grid locators in VHF contests and for awards.

• B. Azimuth and elevation give a direction to point an antenna; a grid locator identifies a place on the Earth.
• C. A grid locator is a location code, not a test instrument for amplifiers.
• D. A grid locator is a location code, not a direction-finding instrument.

B. By using Dual-Tone Multi-Frequency (DTMF) signals

IRLP nodes are controlled over the air with DTMF (touch-tone) signals: you enter the number of the node you want to reach, and a code to disconnect, on your radio's keypad.

• A. IRLP does not use spoken passwords; nodes respond to DTMF codes.
• C. IRLP access is over the air with a radio, not by entering a password on the internet.
• D. CTCSS tones may be needed to access a repeater's receiver, but they do not control IRLP connections.

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

Voice over Internet Protocol (VoIP) converts voice into digital data, sends it over the internet, and converts it back to audio at the other end. Amateur systems such as EchoLink and IRLP use VoIP to link stations and repeaters.

• A. Station identification on linked systems follows the Part 97 identification rules; VoIP is a way to carry voice, not a set of identification rules.
• B. DX stations are spotted through DX cluster and spotting networks, not by VoIP.
• C. Checking a transmitter with remote receivers online is not VoIP, which is a method of carrying voice over the internet.

A. A technique to connect amateur radio systems, such as repeaters, via the internet

The Internet Radio Linking Project (IRLP) connects amateur radio systems, mostly repeaters, through the internet using VoIP. A user on one repeater can talk through a distant repeater that is linked to it through IRLP.

• B. IRLP links radio systems for voice; it does not provide website access over amateur radio.
• C. Real-time information on DX station frequencies comes from DX spotting networks, not IRLP.
• D. Measuring a transmitter's signal strength remotely is done with online receivers, not IRLP.

D. EchoLink

EchoLink lets a licensed amateur connect to EchoLink-enabled repeaters and links from a computer or smartphone over the internet, so a transmission through the repeater can start without using a radio.

• A. IRLP access requires a radio; nodes are controlled over the air with DTMF tones.
• B. D-STAR is a digital voice and data protocol used with D-STAR radios.
• C. DMR is a digital voice protocol used with DMR radios.

C. Register your call sign and provide proof of license

EchoLink allows only licensed amateurs to connect, so each new user registers a call sign and provides proof of license before the account is validated.

• A. EchoLink does not require any training course.
• B. EchoLink software is free for licensed amateurs; no software license is purchased.
• D. Any licensed amateur, including a Technician, may use EchoLink within the privileges of that license.

A. A gateway

A gateway is an amateur station that connects other amateur stations to the internet, for example an EchoLink or IRLP node or an APRS internet gateway (IGate).

• B. A repeater retransmits another station's signal on a different channel (47 CFR 97.3(a)(40)); it does not by itself connect stations to the internet.
• C. A digipeater is a digital repeater that relays packet data over the air, not to the internet.
• D. A beacon transmits for observing propagation and reception (47 CFR 97.3(a)(9)); it does not connect other stations to anything.

D. All these choices are correct

Packet radio, IEEE 802.11 (the Wi-Fi standard, used by amateur mesh networks) and FT8 all send information as digital data, so all are digital communications modes.

• A. Packet radio is a digital mode, but it is only part of the answer.
• B. IEEE 802.11, the Wi-Fi standard, is digital and is used in amateur mesh networks, but it is only part of the answer.
• C. FT8 is a digital mode, but it is only part of the answer.

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

FT8 is a digital mode in the WSJT-X software that exchanges short, structured messages in 15-second transmit periods and can decode signals too weak to hear in the noise. This makes it effective when conditions are poor or power is low.

• A. FT8 is a narrow digital data mode about 50 Hz wide, not wideband FM voice.
• C. FT8 is a single narrow data signal, not a multiplex of channels for repeaters.
• D. FT8 sends short text messages such as call signs, signal reports and grid locators, not images.

D. All these choices are correct

APRS (Automatic Packet Reporting System) carries many kinds of data, including GPS position reports, short text messages and readings from weather stations.

• A. Position reports from GPS receivers are a main use of APRS, but they are only part of the answer.
• B. Text messages can be sent through APRS, but they are only part of the answer.
• C. Weather data from automated stations is sent through APRS, but it is only part of the answer.

C. An analog fast-scan color TV signal

NTSC, named for the National Television System Committee, is the analog color TV standard formerly used for US broadcast television. Analog amateur fast-scan TV in the US uses the same NTSC format, so standard analog TV equipment can display it.

• A. NTSC is an analog TV standard; it is not a digital standard and does not encrypt data.
• B. NTSC is a TV signal standard, not a satellite uplink mode.
• D. NTSC is an analog format; frame compression belongs to digital video systems.

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

APRS combines packet radio with mapping software, so stations' positions appear on a map while operators exchange messages and data in real time. This is useful for coordinating public service events and emergency operations.

• B. APRS does not count PACTOR packets; PACTOR is a separate HF data mode.
• C. Voice links between repeaters over the internet are provided by systems such as IRLP and EchoLink, not APRS.
• D. APRS does not report how many stations are using a repeater.

B. Phase Shift Keying

PSK stands for Phase Shift Keying: data is sent by shifting the phase of the carrier. PSK31, a keyboard-to-keyboard mode used on HF, is an example.

• A. PSK does not involve pulses; it shifts the phase of the carrier.
• C. PSK is not a packet sampling method; the abbreviation stands for phase shift keying.
• D. PSK does not sample power; it shifts the phase of the carrier.

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

DMR (Digital Mobile Radio) uses time-division multiplexing to divide a 12.5 kHz channel into two time slots, so a single repeater can carry two separate digital voice conversations at once.

• B. Automatic position tracking describes APRS, not DMR.
• C. DMR is a digital voice system, not a logging technique.
• D. DMR does not transmit on two repeater inputs at once; it shares one channel between two time slots.

D. All these choices are correct

Packet radio frames include a header with the call signs of the sending and receiving stations and a checksum for detecting errors, and connected-mode packet uses automatic repeat request (ARQ) to resend frames that arrive with errors.

• A. A checksum for error detection is part of each packet, but it is only part of the answer.
• B. A header with the destination station's call sign is part of each packet, but it is only part of the answer.
• C. Automatic repeat request is used in packet radio, but it is only part of the answer.

D. Another name for a Morse code transmission

CW stands for continuous wave and refers to Morse code sent by switching a carrier on and off. Part 97 defines CW emissions as international Morse code telegraphy (47 CFR 97.3(c)(1)).

• A. CW is a transmission method, not a type of propagation.
• B. CW is Morse code, used on every amateur band; the digital mode common on 2-meter FM is packet radio.
• C. Error correction using code words is a feature of digital data modes, not CW.

D. All these choices are correct

The WSJT-X suite includes modes built for weak-signal work, including JT65 and Q65 for Earth-Moon-Earth (moonbounce) contacts, WSPR for weak-signal propagation beacons, and MSK144 for meteor scatter.

• A. Earth-Moon-Earth (moonbounce) is supported, with modes such as JT65 and Q65, but it is only part of the answer.
• B. Weak-signal propagation beacons are supported through WSPR, but they are only part of the answer.
• C. Meteor scatter is supported through MSK144, but it is only part of the answer.

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

ARQ stands for automatic repeat request. The receiving station checks each block of data for errors and asks the sending station to retransmit any block that arrives damaged, so the final message is error-free.

• A. ARQ is used with data of many kinds; it is not a video format.
• B. ARQ does not encrypt anything; it is an error-correction method.
• D. ARQ is an error-correction method based on retransmission; it does not compress data.

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

Amateur mesh networks, such as Broadband-Hamnet and AREDN, use commercial Wi-Fi equipment loaded with modified firmware so it can operate on amateur frequencies that overlap Wi-Fi channels. Each node relays data for the others, forming a self-healing data network.

• B. DMR is a narrowband digital voice mode, not a mesh data network.
• C. Amateur mesh networks are ground-based Wi-Fi data networks, not satellite systems.
• D. Linking repeaters over the internet describes IRLP or EchoLink, not a mesh network.