Audio frequency-shift keying (AFSK) is a frequency modulation method sometimes used when transmitting radioteletype (RTTY) signals.

Frequency-shift keying

Lower sideband (LSB) is normally used for RTTY signals throughout the amateur radio bands when using this method with an SSB transmitter.

There is no technical reason to use LSB instead of USB, however, LSB is conventional.

Mnemonic:

• LSMFT = Lower Sideband Means Fine Teletype

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Mnemonic: The W in Winlink looks like the letter V twice, for VARA.

From Wikipedia: Generally, e-mail communications over amateur radio in the 21st century is now considered normal and commonplace. E-mail via high frequency[b] (HF) can be used nearly everywhere on the planet, and is made possible by connecting an HF single sideband (SSB) transceiver system to a computer, modem interface, and appropriate software. The HF modem technologies include PACTOR, Winmor(deprecated), ARDOP, Vara HF, and Automatic Link Establishment (ALE). VHF/UHF protocols include AX.25 Packet and Vara FM.

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Both PACTOR and VARA are digital modes of communication. If the signal is interfered with, you'd get what you'd expect from interference.

• Frequent retries- due to not hearing each other correctly
• Long pauses- due to never hearing a response
• Failure to establish connection- due to not hearing each other

As such, all choices are correct because all of these are results of interference that prevents stations from hearing each other correctly.

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The reason to look for a clear frequency during the alternate time slot is transmitting during the same time slot will not result in a contact. The calling station will not be able to listen for your transmission at the same time as they also are transmitting. WSJT-X operates by transmitting for about 15 seconds and then listening for about 15 seconds. The program is able to figure out the correct time slot most of the time.

Finding a clear frequency is also important so you are not interfering with transmissions from fellow operators.

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JT-65 and JT-9 are frequency shift keying modes which use a single tone shifted between multiple frequencies over time. Most of the available software which support them are designed to interface with a radio via an Audio (sound-card) interface (the "A" in AFSK) while the radio is operated in a single sideband mode using the upper sideband.

As with all questions pertaining to the use of Upper or Lower sideband, The use of Upper Sideband is an artifact of custom and convention rather than a stringent technical requirement. Nearly all digital modes which employ computer-based audio interfaces are operated with Upper Sideband modulation.

When you use a computer, think USB, Except for RTTY which uses LSB here in the States.

Computers use USB connectors all the time..

HINT: J2T served at a USafB-ase.

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Amateur radio transmissions of radioteletype (RTTY) signals use methods of frequency-shift keying (FSK). Two frequencies, known as the mark and space tones are used. The difference between these two frequencies is known as the frequency shift. The amount of shift most frequently used on the HF bands for amateur operators is a 170 Hz difference.

For more info see Wikipedia: RTTY

Silly hint: The letter "R" (in RTTY) is the 18th letter of the alphabet. The first two digits of the correct answer (17) is the closest number to 18.

Major System 170 = ticks, the sound an old teletype makes.

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Because FT8 operates on strict 15 second transmit windows, time must be accurate. The protocol can generally support plus or minus one second of time differential.

It is important that FT8 users synchronize their clocks against a known source such as a reputable NTP pool.

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PSK31, or Phase-Shift Keying at 31 baud, is a data transmission method. On bands where the FCC has indicated specific areas for CW/data versus phone operations, the data modes are allocated to the lower frequency end of the range. PSK31 is most similar to RTTY, and so on the 20 meter band is assigned to the area below the RTTY segment, near 14.070 MHz.

Notes: Slow scan TV is in the image/voice section at the upper end of the band, just above the SSB phone segment. The CW range is contiguous, not having anything stuck in the middle like one (incorrect) distracter suggests.

Probably the best way to remember this is to know that RTTY (Radio Teletype) is also a "digital mode" and is the most similar to PSK31 of all the options listed; PSK31 is just below the RTTY segment, putting the two digital modes together.

Hint: The only answer that gives specific frequencies.

For more info see: ARRL Band Plan for RTTY/Data Frequencies.

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A robust network of PACTOR stations has been established to relay data between radio stations and the Internet, extending Internet access to sea based and other isolated users

PACTOR is basically like a short wave wireless internet connection. A request is made to a certain destination. The destination receives the request and responds to the sender. The communication is only intended to reach a specific destination from a specific destination. It is a point to point protocol.

Suggest key: PACTOR is Pact with Two :P

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Transmit a connect message on the station’s published frequency. You can find this frequency in a repeater guide.

As with FM repeaters, you may contact the gateway at any time.

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This service allows fast communication between stations to coordinate and transfer information and data without the internet.

Hint: This is the only answer that talks about an Emergency, which is also in the question.

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Winlink is a versatile and varied form of communication for the Amateur Radio Operator. It can be used for sending and receiving emails either from fellow Winlink users or from regular email client users via the internet. This is accomplished by transmitting to known stations that relay your emails to and from the internet. Messages and files can also be sent and received point to point with fellow operators with no relay station needed. This can be helpful when access to the internet is not possible or needed. Both forms of Winlink transmissions can be used over VHF or HF, for longer or shorter communication needs.

Winlink is also a form of packet radio because it breaks the user's transmissions into discreet packets of data for easier transfer of data, and error correction, thus allowing for error-free communications.

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A gateway provides a connection between networks and contains devices and here, the server connects the ham radio and the Internet so it acts as a gateway.

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The mark and space frequencies represent \(1\) and \(0\) in a signal. If these are reversed, the signal becomes corrupted. The signal \(0101\) is not the same as \(1010\).

The side band is a pure chunk of bandwidth and though it may appear to be tuned properly the wrong one can be selected, throwing off decoding.

The baud rate is the symbol or modulation rate. The baud rates on the sending and receiving ends must match in order for a signal to be properly decoded.

Therefore, All of these choices are correct.

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FT8 is a digital mode, so it may only be operated within the data portion of the band- specifically- the RTTY portion of the band. For 20m, this is 14.070-14.095 MHz.

See the ARRL band plan for more details

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