E2 Operating Procedures

C. From south to north

An ascending pass is one in which the satellite moves from south to north across your sky, on the part of its orbit after it crosses the equator heading north (the ascending node). A pass moving from north to south is a descending pass.

• A. Ascending and descending describe north and south motion, not west to east motion.
• B. Ascending and descending describe north and south motion, not east to west motion.
• D. A satellite moving from north to south is on a descending pass.

D. All these choices are correct

An inverting linear transponder mixes its uplink passband with a local oscillator and transmits the difference, which turns the passband upside down. As a result, a signal near the top of the uplink passband comes out near the bottom of the downlink, upper sideband becomes lower sideband, and the Doppler shifts on the uplink and downlink act in opposite directions and partly cancel.

• A. Reduced Doppler shift is a real effect of an inverting transponder, but signal position and sideband are also reversed, so this is only part of the answer.
• B. Reversal of signal position in the passband is true, but Doppler reduction and sideband inversion also occur, so this is only part of the answer.
• C. Sideband inversion is true, but position reversal and Doppler reduction also occur, so this is only part of the answer.

D. The signal is mixed with a local oscillator signal and the difference product is transmitted

An inverting linear transponder mixes the received uplink signal with a local oscillator and transmits the difference product (local oscillator frequency minus uplink frequency). Because the output is the oscillator frequency minus the input, a higher uplink frequency produces a lower downlink frequency, which inverts both the passband and the sideband.

• A. A linear transponder does not detect and remodulate signals; it shifts the whole passband in frequency, which leaves every signal's modulation intact.
• B. A linear transponder must stay linear so SSB and CW signals pass without distortion; it does not pass signals through a nonlinear filter.
• C. Filtering out a Q component would destroy information; the transponder shifts the passband without breaking signals into I and Q components.

B. The satellite’s uplink and downlink frequency bands

A satellite's mode names the frequency bands used for its uplink and downlink. For example, mode U/V means the satellite receives on 70 cm (UHF) and transmits on 2 m (VHF).

• A. Low earth or geostationary describes the orbit, not the mode.
• C. The satellite's orientation, or attitude, is not what mode means.
• D. Polar or equatorial describes the orbit's inclination, not the mode.

D. The uplink and downlink frequency ranges

The letters in a satellite mode designator name the uplink and downlink frequency bands, uplink first: V is 2 m, U is 70 cm, L is 23 cm and S is 13 cm. Mode V/U, for example, means the satellite listens on 2 m and transmits on 70 cm.

• A. Mode letters say nothing about power limits.
• B. Mode letters do not identify the location of a ground control station.
• C. Polarization is not part of the mode designator.

A. Parameters that define the orbit of a satellite

Keplerian elements are the set of numbers that define a satellite's orbit, such as inclination, eccentricity, mean motion and the epoch time at which they apply. Tracking programs use current elements to predict when a satellite will be in view and where to point the antenna.

• B. Yagi elements are physical parts of an antenna; Keplerian elements describe orbits.
• C. Keplerian elements have nothing to do with tube heaters; the name refers to orbital parameters.
• D. Keplerian elements are not codes of any kind; spread spectrum uses spreading sequences, not orbital data.

D. All these choices are correct

A linear transponder translates everything in its uplink passband to the downlink without demodulating it, so any signal type that fits can be relayed: FM, CW, SSB, SSTV, PSK and packet. SSB and CW are preferred in practice, because a constant-power FM signal takes a large share of the transponder's limited output power.

• A. FM and CW can pass through a linear transponder, but so can the other listed signal types.
• B. SSB and SSTV can pass through a linear transponder, but so can FM, CW, PSK and packet.
• C. PSK and packet can pass through a linear transponder, but so can the other listed signal types.

B. To avoid reducing the downlink power to all other users

A linear transponder's limited output power is shared by all the signals in its passband, so an uplink signal stronger than necessary takes more than its share. That leaves less downlink power for every other user, which is why stations use only enough ERP toward the satellite to be heard.

• A. Uplink power does not create errors in the satellite's telemetry; the concern is how the transponder's output power is shared.
• C. Excess uplink power does not make the satellite transmit outside its downlink band; the concern is that it takes downlink power from other users.
• D. Interference to terrestrial contacts is a general concern, but the reason specific to a linear transponder is that excess uplink power takes downlink power from other users.

A. The 23- and 13-centimeter bands

In amateur satellite work, L band means the 23 cm band (around 1.2 GHz) and S band means the 13 cm band (around 2.4 GHz), borrowing the radar band letters for 1 to 2 GHz and 2 to 4 GHz. The letters appear in satellite mode designators.

• B. The 2 m and 70 cm bands are designated V and U, not L and S.
• C. L and S name frequency bands, not types of message systems.
• D. L and S name frequency bands; they say nothing about which sideband to use.

B. Geostationary

A geostationary satellite orbits about 35,800 km above the equator in the same direction the Earth rotates, completing one orbit per day, so it appears to stay in one position in the sky. A ground station can aim its antenna once and leave it.

• A. A satellite in a highly elliptical orbit (HEO) moves slowly near its high point but still moves across the sky.
• C. Geomagnetic refers to the Earth's magnetic field, not a type of orbit.
• D. A low earth orbit (LEO) satellite crosses the sky in a matter of minutes.

B. A circularly polarized antenna

A circularly polarized antenna receives a linearly polarized signal at any orientation with a constant 3 dB loss, so changes in the signal's polarization do not cause deep fades. That makes it effective against spin modulation (polarization changing as the satellite rotates) and Faraday rotation (the ionosphere rotating the polarization).

• A. A linearly polarized antenna fades whenever the incoming polarization rotates away from it, which is the problem being solved.
• C. An isotropic antenna is a theoretical reference used for comparing gain; it cannot be built.
• D. A log-periodic dipole array is linearly polarized, so it suffers the same polarization fading.

C. To hold digital messages in the satellite for later download

A store-and-forward satellite receives digital messages, holds them in onboard memory, and transmits them later, for example when it passes over the destination station. This lets stations that never see the satellite at the same time exchange messages.

• A. Uploading operational software is a command function; store-and-forward handles user messages.
• B. Store-and-forward does not delay telemetry between satellites; it holds messages for later download to the ground.
• D. Relaying messages between satellites is an inter-satellite link, a different function from holding messages for later download.

A. 25% of the data sent is forward error correction data

A forward error correction (FEC) coding rate of 3/4 means that for every 4 bits transmitted, 3 are user data and 1 is redundant error correction data. So 1/4, or 25%, of the data sent is FEC.

• B. Coding rate describes error correction overhead, not data compression.
• C. The guard interval is a separate DVB-T setting (for example 1/4 or 1/8 of the symbol time), not the coding rate.
• D. Coding rate is not a pixel encoding scheme; it is the share of transmitted bits that carry user data.

C. 525

An NTSC fast-scan television frame has 525 horizontal lines, sent as two interlaced fields of 262.5 lines each, at about 30 frames (60 fields) per second.

• A. 30 is the approximate number of frames per second, not lines per frame.
• B. 60 is the approximate number of fields per second, not lines per frame.
• D. 1080 is the line count of a high-definition format, not NTSC.

D. By scanning odd-numbered lines in one field and even-numbered lines in the next

Interlaced scanning splits each NTSC frame into two fields: one field scans the odd-numbered lines and the next scans the even-numbered lines between them. Together the two fields form a full frame, which reduces flicker without doubling the bandwidth.

• A. The two fields are scanned one after the other, not at the same time.
• B. Each field is scanned from top to bottom.
• C. Every line is scanned left to right; interlacing changes which lines each field scans, not the scan direction.

A. Color lines are sent sequentially

Analog SSTV sends color by scanning each picture line separately for each color component, one after another; the Martin and Scottie modes, for example, send green, blue and red scans for each line. The receiving software combines the sequential scans into a color image.

• B. Analog SSTV has no 2.8 kHz color subcarrier; each color scan is carried by the tone frequency.
• C. A color burst belongs to fast-scan NTSC television, where it is sent near the start of each line, not to SSTV.
• D. SSTV does not add amplitude modulation for color; picture information is carried by tone frequency only.

C. Vestigial sideband reduces the bandwidth while increasing the fidelity of low frequency video components

An analog fast-scan TV signal is amplitude modulated, and sending both full sidebands would double its bandwidth. Vestigial sideband sends one full sideband plus a small part (vestige) of the other near the carrier, which cuts bandwidth while preserving the low-frequency video components that a sharp single-sideband filter would distort.

• A. TV audio is sent on a separate FM sound carrier, not in the vestigial sideband.
• B. Color (chroma) information is on a subcarrier in the full sideband, not in the vestige.
• D. Vestigial sideband is a bandwidth technique; it does not emphasize high frequencies or sharpen the picture.

A. Amplitude modulation in which one complete sideband and a portion of the other are transmitted

Vestigial sideband (VSB) modulation is amplitude modulation in which one sideband is transmitted completely and only a portion, or vestige, of the other sideband is transmitted. Analog fast-scan TV uses it to save bandwidth compared with full double-sideband AM.

• B. VSB does not invert a sideband; it removes most of one sideband.
• C. VSB is a form of amplitude modulation, not narrow-band FM.
• D. VSB is not spread spectrum and does not combine FM with SSB.

B. QAM and QPSK

DVB-T (Digital Video Broadcasting, Terrestrial) uses OFDM, with many subcarriers each modulated by QPSK or QAM (16-QAM or 64-QAM). QPSK is more robust for weak signals, while higher-order QAM carries more data in the same bandwidth.

• A. FM is used for analog FM television and FSK for some data modes, not for DVB-T.
• C. AM is used for analog fast-scan TV and OOK (on-off keying) is CW-style keying; neither is used for DVB-T.
• D. Only QAM and QPSK are used for DVB-T, so not all the choices are correct.

A. Transmitting on channels shared with cable TV

Some 70 cm amateur frequencies coincide with analog cable TV channels; for example, 439.25 MHz is the video carrier frequency of cable channel 60. A cable-ready analog TV receiver can tune these channels, so it can receive amateur fast-scan TV transmitted there.

• B. Satellite TV dishes are microwave antennas; they do not let a TV receiver tune 70 cm signals.
• C. TV channel 2 occupies 54 to 60 MHz, nowhere near the 70 cm band, and it is not an amateur frequency.
• D. Fast-scan TV needs several MHz of bandwidth, far more than an SSB receiver's roughly 3 kHz passband and a sound card can handle.

D. SSB

Digital Radio Mondiale (DRM) SSTV, used by amateur programs such as EasyPal, sends images as an OFDM digital signal less than 3 kHz wide that fits through the audio passband of an SSB transceiver. The receiving station uses an SSB receiver and decodes the audio with computer software.

• A. CDMA is a cellular telephone access method, not a receiver type for SSTV.
• B. AREDN is amateur mesh networking firmware for wireless routers, not an SSTV receiver.
• C. Amateur DRM SSTV is transmitted as SSB, and an AM receiver does not demodulate SSB properly.

A. Tone frequency

In analog SSTV, brightness is set by the tone frequency: about 1500 Hz represents black and 2300 Hz represents white, with frequencies in between for shades of gray. Sync pulses use a separate 1200 Hz tone.

• B. Analog SSTV is a constant-amplitude audio signal; tone amplitude carries no picture information.
• C. Sync pulses mark the timing of lines; they do not carry brightness.
• D. The sync frequency is fixed at 1200 Hz and marks timing, not brightness.

B. To identify the SSTV mode being used

The VIS (vertical interval signaling) code is a short digital code sent at the start of an SSTV image that tells the receiving software which SSTV mode, such as Scottie 1 or Martin 1, follows. The software can then switch to that mode automatically.

• A. Analog SSTV has no color burst oscillator; color is sent as sequential scans.
• C. Synchronization comes from the sync pulses; the VIS code identifies the mode.
• D. The VIS code does not carry a call sign; station identification is sent separately.

A. Specific tone frequencies

SSTV receiving software recognizes the start of each picture line by a sync pulse at a specific tone frequency, 1200 Hz, which lies below the 1500 to 2300 Hz range used for picture content. Locking to these pulses keeps the lines aligned.

• B. Each mode has a fixed line time, but the software relies on the sync tone to mark when a line begins rather than on elapsed time alone.
• C. SSTV tones have constant amplitude; line starts are marked by tone frequency, not amplitude.
• D. Line sync uses a single tone frequency, not a two-tone signal.

D. No additional indicator is required

When a US licensee operates a remotely controlled station located in the US, normal station identification applies: the station's call sign at the end of each communication and at least every 10 minutes (47 CFR 97.119(a)). Part 97 does not require any indicator showing where the remote transmitter is located.

• A. No rule requires a state abbreviation indicator; self-assigned indicators are optional (97.119(c)).
• B. No rule creates a /R# indicator for remote stations.
• C. ARRL sections are used in some contest exchanges, but no rule requires them as an indicator.

C. ADIF

ADIF (Amateur Data Interchange Format) is the standard file format for exchanging log data between logging programs and online logbooks. An ADIF file stores each contact as tagged fields such as call sign, date, time, band and mode.

• A. NEC (Numerical Electromagnetics Code) is an antenna modeling engine, not a log format.
• B. ARLD is not a standard amateur log file format.
• D. OCF is not a standard amateur log file format.

A. 30 meters

By widely followed convention in amateur band plans, contests are not held on the WARC bands (30, 17 and 12 m). The 30 m band is also poorly suited to contesting: it is only 50 kHz wide, has no phone privileges, and limits every station to 200 W PEP (47 CFR 97.313(c)(1)).

• B. 6 m is included in VHF contests and is active during them.
• C. 70 cm is included in VHF and UHF contests.
• D. 33 cm is included in VHF and UHF contests.

B. Frequencies shared with various unlicensed wireless data services

Amateur mesh networks, such as AREDN, run modified Wi-Fi equipment on amateur frequencies that overlap unlicensed wireless data bands, such as parts of the 2.4 GHz and 5.8 GHz amateur allocations. Operating there under Part 97 means the traffic must follow amateur rules, including the ban on encryption.

• A. HF data signals are limited to 2.8 kHz bandwidth (47 CFR 97.307(f)(3)), far too narrow for a broadband mesh network.
• C. Cable TV channels are carried on cable systems, and channels 41 to 43 do not correspond to an amateur band.
• D. The 60 m channel at 5373 kHz is limited to 2.8 kHz bandwidth and cannot support a broadband network.

B. Handle the receiving and sending of confirmations for a DX station

A DX QSL manager handles QSL cards and other contact confirmations for a DX station, receiving requests and sending confirmations so the DX operator can concentrate on operating. QSL managers are common for DXpeditions and stations in rare locations.

• A. No one allocates frequencies for DXpeditions; they choose frequencies within the rules of the country they operate from.
• C. A net that lines up callers for a DX station is run by a net control station, not a QSL manager.
• D. Passing propagation and pileup information to a DXpedition is the job of a pilot station, not a QSL manager.

C. In the weak signal segment of the band, with most of the activity near the calling frequency

On VHF and UHF, SSB and CW activity is concentrated in the weak signal segment near the bottom of each band, around calling frequencies such as 50.125 MHz, 144.200 MHz and 432.100 MHz. During contests, activity clusters near these calling frequencies and spreads out from them.

• A. There are no contest segments at the top of the VHF and UHF bands; the upper parts are mostly used for FM, repeaters and other modes.
• B. The middle of these bands is mostly FM and repeater territory, and the national FM simplex calling frequencies are not where SSB and CW contest activity happens.
• D. SSB and CW activity is not offset 25 kHz above a mid-band calling frequency; it centers on the weak signal calling frequencies.

A. A standard for submission of electronic contest logs

Cabrillo is a standard text file format for submitting contest logs electronically to contest sponsors. Logging programs export a Cabrillo file with header lines describing the entry and one line per contact.

• B. The information exchanged during a contest contact is the exchange set by each contest's rules, not Cabrillo.
• C. Each contest sets its own rules; Cabrillo is a log format, not a rule set.
• D. Digital modes such as FT4 are designed for rapid contest exchanges; Cabrillo is a log file format, not a transmission protocol.

D. All these choices are correct

Logbook of The World (LoTW), run by the ARRL, confirms a contact when both stations upload matching, digitally signed records, and those confirmations count toward awards such as DXCC and Worked All States. Domestic, international and special event contacts can all be confirmed this way.

• A. Special event contacts within the US can be confirmed through LoTW, but so can the other types listed.
• B. Contacts between US and non-US stations can be confirmed through LoTW, but this is only one of the types listed.
• C. Worked All States credit is available through LoTW, but so are the other types listed.

C. A wireless router running custom firmware

Amateur mesh networks are commonly built from commercial wireless routers or outdoor Wi-Fi radios loaded with custom firmware, such as AREDN, that lets them operate on amateur frequencies and link to each other automatically.

• A. A 2 m transceiver with a 1,200 baud modem is a packet radio station, far slower than a Wi-Fi based mesh network.
• B. EchoLink links voice radio users through the internet; it does not build a mesh network.
• D. A 440 MHz transceiver with a 9,600 baud modem is a packet radio station, much slower than Wi-Fi based mesh links.

D. All these choices are correct

DX stations often work split, transmitting on one frequency and listening on another, for several reasons: the DX station may be on a frequency that some callers may not use, moving the callers elsewhere keeps them from covering the DX signal, and the result is more efficient operating with less interference.

• A. True: for example, a DX station in another ITU Region may operate phone below 7.125 MHz, where most US stations may not, but this is only one of the reasons.
• B. True: putting callers on a separate frequency keeps the DX station audible, but this is only one of the reasons.
• C. True: split operation reduces interference and improves efficiency, but this is only one of the reasons.

A. Send your full call sign once or twice

In a pileup or contest, send your full call sign once or twice, then listen. A complete call lets the DX station copy you correctly, while repeating it many times or sending only part of it slows the exchange.

• B. Sending only part of your call sign causes confusion and does not identify your station.
• C. A grid square is not needed when calling unless the exchange specifically asks for it.
• D. Sending the DX station's call and your own three times each wastes time; the DX station already knows its own call sign.

C. Latency

Latency is the delay between an action and its effect, such as the time from pressing a remote station's transmit control to the signal actually going out. Remote operation over the internet adds latency, which operators must allow for in fast exchanges such as contest CW.

• A. Jitter is variation in delay from moment to moment, not the delay itself.
• B. Hang time is how long a VOX circuit or repeater keeps transmitting after its input stops.
• D. Anti-VOX keeps receiver audio from the speaker from triggering the VOX.

B. MSK144

MSK144 is a WSJT-X digital mode designed for meteor scatter, repeating short message frames so a complete message can be decoded from the brief reflection of a single meteor trail. It is used mainly on 6 m and 2 m.

• A. WSPR is a weak signal beacon mode for studying propagation, not a meteor scatter mode.
• C. Hellschreiber is a facsimile-style text mode that paints characters as images, not a meteor scatter mode.
• D. APRS is a packet system for position reports and short messages, not a meteor scatter mode.

D. Grid square

In VHF contests, FT8 and FT4 standard messages carry the station's 4-character Maidenhead grid square in place of the signal-to-noise report, because VHF contest exchanges are based on grid squares, which serve as multipliers.

• A. RST reports are not part of the VHF contest exchange; the grid square is.
• B. State abbreviations are part of some HF contest exchanges, but VHF contests use grid squares.
• C. Serial numbers are used in some contests, but VHF contest messages carry the grid square.

D. Q65

Q65 is a WSJT-X digital mode designed for weak signal paths such as Earth-Moon-Earth (EME), where echoes are below the noise and spread in frequency by Doppler effects. It can average several transmissions of the same message to decode one too weak to copy in a single period.

• A. MSK144 is designed for meteor scatter, not EME.
• B. PACTOR III is an HF data mode for message transfer, not EME.
• C. WSPR is a propagation beacon mode, not a mode for EME contacts.

C. APRS

APRS (Automatic Packet Reporting System) sends GPS position reports as packet radio data, commonly on 144.39 MHz in North America, and digipeaters and internet gateways pass them to online maps. High-altitude balloons carry APRS trackers so their flights can be followed in real time.

• A. FT8 is used for weak signal contacts, not real-time position tracking.
• B. LORAN was a land-based radionavigation system; there is no bandwidth compressed version used for balloon tracking.
• D. PACTOR III is an HF message transfer mode, not a position tracking system.

B. Decodes signals with a very low signal-to-noise ratio

JT65 is a WSJT digital mode designed to decode signals with very low signal-to-noise ratios, down to about -25 dB measured in a 2500 Hz bandwidth, using strong error correction and one-minute transmit periods. That makes it useful for EME and weak signal HF work.

• A. JT65A occupies about 178 Hz, not 65 Hz; the 65 refers to its 65 tones.
• C. JT65's symbol rate is about 2.7 baud; the 65 is the number of tones, not the symbol rate.
• D. JT65 sends short text messages, not fast-scan TV images.

A. Time-synchronous transmissions alternating between stations

EME contacts are made by stations taking turns transmitting in fixed, clock-synchronized periods (for example, one-minute periods in JT65), so each station knows exactly when to transmit and when to listen for the weak echo of the other station's signal.

• B. Storing and forwarding digital messages is a satellite and packet technique, not an EME method.
• C. EME schedules are based on when the Moon is visible to both stations, not on monitoring beacons reflected from the Moon.
• D. EME signals are weak, so slow CW or digital modes are used; high-speed CW is associated with meteor scatter.

C. AX.25

APRS uses the AX.25 amateur packet radio protocol, sending its position reports and messages as AX.25 frames, usually at 1200 baud on VHF.

• A. PACTOR is an HF ARQ data mode, not the APRS protocol.
• B. QAM is a modulation method, not a link protocol, and it is not used for APRS.
• D. AMTOR is an older HF teleprinting mode, not used for APRS.

C. Unnumbered Information

APRS beacons are sent as AX.25 Unnumbered Information (UI) frames, which are connectionless: they go out to any station that hears them, with no connection setup and no acknowledgment. That suits one-to-many position reports.

• A. Acknowledgment frames belong to connected-mode packet sessions, not APRS beacons.
• B. Burst is not an AX.25 frame type.
• D. Connect frames set up a two-station connected session; APRS beacons need no connection.

A. Multitone AFSK

JT65 uses multitone AFSK: the software generates one of 65 audio tones for each symbol and feeds it into an SSB transmitter, which produces a frequency-shift keyed RF signal.

• B. PSK shifts the phase of a carrier; JT65 shifts frequency among many tones.
• C. RTTY is two-tone FSK using the Baudot code, not JT65's 65-tone scheme.
• D. QAM varies both amplitude and phase; JT65 uses frequency shifts only.

C. Three digipeater hops are requested with one remaining

In an APRS path such as WIDE3-1, the first number is the number of digipeater hops requested and the second is the number of hops remaining; each digipeater that relays the packet reduces the second number by one. WIDE3-1 means 3 hops were requested and 1 remains, so 2 digipeaters have already relayed the packet.

• A. The path does not limit how many stations may use the frequency.
• B. APRS paths have nothing to do with subcarriers.
• D. The WIDEn-N path counts digipeater hops, not internet gateway stations.

D. By packet digipeaters

APRS data is relayed over the air by packet digipeaters (digital repeaters), which receive AX.25 packets and retransmit them according to the path in each packet. Internet gateways (igates) pass the packets to the internet.

• A. APRS beacons are not acknowledged, so there is no ACK/NAK relay.
• B. C4FM repeaters carry Yaesu System Fusion digital voice, not APRS packets.
• C. DMR repeaters are digital voice systems; APRS packets are relayed by AX.25 digipeaters.

B. FSK

Data emissions below 30 MHz commonly use frequency shift keying (FSK), either by shifting the transmitter frequency directly or by feeding audio tones into an SSB transmitter (AFSK). RTTY and many other HF data modes work this way.

• A. DTMF tones on FM are used for signaling and control on VHF and UHF, not for HF data emissions.
• C. Pulse emissions are authorized only on certain bands at 902 MHz and above (47 CFR 97.305(c)).
• D. Spread spectrum is authorized only above 222 MHz (47 CFR 97.305(c)).

B. Synchronization of computer clocks

WSJT-X modes such as FT8 transmit and receive in fixed time slots, so each station's computer clock must be closely synchronized to UTC, generally within about a second, using internet time or GPS. A clock that drifts too far causes decodes to fail.

• A. Frequency shifts carry the data; they do not set the timing of transmit and receive periods.
• C. No sync field transmission sets the timing; transmit and receive periods start on clock time.
• D. No timing pulses set the periods; the computer clock does.

B. Four-tone continuous-phase frequency shift keying

FT4 uses four-tone continuous-phase frequency shift keying (4-GFSK, a smoothed form of 4-FSK), and the 4 in its name refers to those four tones. It uses 7.5 second transmit and receive periods for fast contest exchanges.

• A. FT4 sends a 77-bit message, like FT8; the 4 does not refer to multiples of 4 bits.
• C. FT4's timing is built on 7.5 second periods, but the 4 in the name refers to its four tones, not to a count of cycles.
• D. Only the four-tone FSK explanation is correct, so not all the choices are correct.

D. All these choices are correct

FST4 is a WSJT-X mode for weak signal work on LF, MF and HF that uses four-tone Gaussian frequency shift keying (4-GFSK). It offers seven transmit/receive period lengths, from 15 seconds up to 30 minutes, and its tone spacing changes with the period length, giving seven tone spacings.

• A. Four-tone GFSK is true of FST4, but it also has variable periods and seven tone spacings, so this is only part of the answer.
• B. Variable transmit/receive periods are true of FST4, but this is only part of the answer.
• C. Seven tone spacings are true of FST4, but this is only part of the answer.

A. WSPR

WSPR (Weak Signal Propagation Reporter) is a beacon mode: stations send a fixed message with call sign, grid square and power, and receiving stations report what they decode to an online database. It is not designed for typing messages back and forth.

• B. RTTY is a keyboard-to-keyboard mode.
• C. PSK31 is a keyboard-to-keyboard mode.
• D. MFSK16 is a keyboard-to-keyboard mode.

C. 15 seconds

FT8 uses 15 second transmit and receive periods synchronized to UTC, with each transmission lasting about 12.6 seconds. Stations take turns in alternating periods.

• A. FT8 transmissions have a fixed length regardless of the message content.
• B. The 8 in FT8 refers to its eight tones, not an 8 second cycle.
• D. FT8 periods are 15 seconds, not 30.

C. Multiple receive cycles are averaged

Q65 can average the received signals from several transmit periods of the same message, so a signal too weak to decode in one period can be decoded after a few repeats. That ability suits it to EME and scatter paths where signals are near or below the noise.

• A. Like JT65, Q65 sends short structured messages, not free-form keyboard-to-keyboard text.
• B. Q65 is a 65-tone frequency shift keying mode like JT65; the Q does not stand for quadrature modulation.
• D. Keyboard-to-keyboard operation and quadrature modulation are not features of Q65, so not all the choices are correct.

B. PACTOR

PACTOR is an ARQ (automatic repeat request) data mode that sends error-checked packets and can carry any 8-bit data, so it can transfer binary files such as compressed email attachments. Winlink uses PACTOR on HF for this reason.

• A. PSK31 sends text characters using Varicode and has no error-checked file transfer.
• C. RTTY uses the 5-bit Baudot code, which carries only letters, figures and a few symbols.
• D. AMTOR carries a limited text character set, like RTTY, and cannot carry arbitrary binary data.

D. PSK31

PSK31 uses Varicode, a variable-length character code in which common characters such as lowercase e have short codes and rare characters have longer ones, much like Morse code. This keeps the average character short so the slow 31.25 baud signal can keep up with typing.

• A. RTTY uses Baudot, a fixed-length 5-bit code.
• B. PACTOR transmits data in fixed-length, error-checked packets; the mode associated with a variable-length character code is PSK31.
• C. MT63 sends characters as fixed-length codes spread across 64 tones.

C. FT8

FT8 uses 8 tones spaced 6.25 Hz apart, so its signal occupies only 50 Hz. By comparison, 45 baud RTTY with 170 Hz shift takes roughly 250 Hz, MFSK16 roughly 300 Hz, and PACTOR IV about 2.4 kHz.

• A. MFSK16 occupies roughly 300 Hz, several times wider than FT8's 50 Hz.
• B. 45 baud RTTY with 170 Hz shift occupies roughly 250 Hz, about five times FT8's 50 Hz.
• D. PACTOR IV uses about 2.4 kHz, nearly the full width of an SSB channel.

A. Direct FSK modulates the transmitter VFO

Direct FSK shifts the transmitter's own oscillator (VFO) between the mark and space frequencies, keyed by a data line, while audio FSK (AFSK) feeds audio tones into an SSB transmitter, which converts them into RF frequency shifts. Both can produce the same RF signal; the difference is how it is generated.

• B. Bandwidth depends on the shift and the symbol rate, not on whether the shift is made directly or with audio tones.
• C. Direct FSK does not inherently allow higher baud rates than AFSK.
• D. Only the statement about modulating the VFO is correct, so not all the choices are correct.

A. ALE constantly scans a list of frequencies, activating the radio when the designated call sign is received

Automatic Link Establishment (ALE) radios continuously scan a list of channels. A calling station sends a call containing the address (call sign) of the station it wants, and when a scanning radio hears its own address it stops on that channel and alerts the operator or links automatically.

• B. ALE works over the radio channels themselves and does not depend on an internet site.
• C. ALE does not send a constant tone; it sends digital calling signals on the scanned channels.
• D. ALE does not rely on hearing its own signal echoed by backscatter.

D. PACTOR IV

PACTOR IV is a wideband (about 2.4 kHz) adaptive HF data mode that can reach several kilobits per second on a good path, far more throughput than narrow keyboard and weak signal modes. It adjusts its speed to conditions, so its full rate is available only when the path is clear.

• A. MFSK16 is a keyboard mode with a throughput of a few tens of bits per second.
• B. 45 baud RTTY sends about 6 characters per second (60 words per minute), far below PACTOR IV.
• C. FT8 sends a 77-bit message every 15 seconds, about 5 bits per second, which suits weak signal contacts rather than data throughput.