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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The correct answer is: Put the modem or controller in a mode which allows monitoring communications without a connection

Short answer:

PACTOR is a radio modulation mode used to send and receive digital information via radio.

PACTOR radio equipment consists of an HF transceiver, a computer and a terminal node controller. Software running on the computer drives the terminal node controller.

The calling modem uses the PACTOR-I FSK connect frame to be compatible with the lowest level. The called modem then answers and the modems negotiate to the highest possible level both modems are capable of. The computer can be placed in a mode to listen on a channel without actually making a modem connection.

Longer more-detailed answer:

PACTOR is a radio modulation mode used by amateur radio operators, marine radio stations, and radio stations in isolated areas to send and receive digital information via radio. It was developed by a German company Special Communications Systems GmbH (SCS).

PACTOR combines the bandwidth efficiency of packet radio with the error-correction (CRC) and automatic repeat request (ARQ) of AMTOR (Amateur Teleprinting Over Radio)

PACTOR radio equipment consists of an HF transceiver, a computer and a terminal node controller. Software running on the computer drives the terminal node controller.

There are three versions of PACTOR protocol, Version 1 2 and 3. Version 1 is open source and widely used but slow. PACTOR 2 and 3 are proprietary to SCS and require licensing and critics say is very expensive, but greatly increases the throughput of data.

To create a connection, The calling modem uses the PACTOR-I FSK connect frame to be compatible with the lowest level. The called modem then answers and the modems negotiate to the highest possible level both modems are capable of.

Sources: http://www.scs-ptc.com/pactor/pactor and enter link description here

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PACTOR and WINMOR are both digital modes; if signals interfere with them the results will be exactly what you'd expect when stations aren't able to hear each other:

• frequent retries (didn't hear it correctly),
• timeouts (failed to ever hear it correctly),
• long pauses in transmission (because it doesn't hear the response), and
• failure to establish a connection between stations (because they can't hear each other).

So all of these choices are correct because these are all things that result when interference prevents the stations from accurately hearing each other.

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Band plans are organized so that each transmission type uses its own portion of the band frequency. On bands where the FCC designates areas for data versus phone transmissions, data transmission frequencies are located in the lower frequency portion of the band. The 20 meter band allows a General Class licensee to use the range from 14.025 - 14.150 MHz for CW and data communications. The section set aside WITHIN that segment for use by RTTY/Data transmissions is the portion of that segment from 14.070 - 14.100 MHz.

Note: Only 14.070 - 14.100 MHz falls within the CW/data section of the whole 20 meter band. 14.000 - 14.050 MHz falls below the frequency privileges, 14.150 - 14.225 MHz is the frequency gap between the data and voice segments, and 14.275 - 14.350 MHz is the range for the voice segment of the band. If you look at the frequencies from the bottom to the top of the range, data is located in the allowed lower section of the range, it is fairly easy to pick out 14.070 - 14.100 MHz as the correct segment.

For more info go to: ARRL Band Plan for RTTY/Data Frequencies

**
Silly Hint: Remember "2" and "0" (as in 20 meter band), and that only one of the answers ends in "0" (14.070) and "2" (14.112).

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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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The FCC allows General Class license privileges on the 80 meter CW/data band from the range of 3525 to 3600 kHz. The band plans set aside portions within each band to indicate specific types of transmissions within each band segment. The portion of the 80 meter band set aside for data transmissions, such as RTTY, is from 3570 to 3600 kHz.

Note: Answer "3500-3525" is below the frequencies allowed, and both "3700-3750" and "3775-3825" fall at least partially within the gap between the 80 meter data segment and the 75 meter voice segment of the band. Therefore 3570 to 3600 kHz is the only valid answer.

Silly hint: When calculating the frequency for 80 meters, you get 300 / 80 = 3.75MHz. Only one answer includes the numbers 3, 7, and 5, and a zero in the first position, which is "3570 to ..."

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

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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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Overmodulation is an often occurring "gotcha" for many new hams intending to work PSK31. The PSK mode requires modulation audio from your computer. However, if the audio volume/amplitude is too high, your radio has no choice but to distort the signal through the use of ALCs (Auto Levelling Circuits). If you're familiar with audio production, this is a similar process equivalent to Dynamic Range Compression.

The ALC prevents the signal from clipping, but introduces harmonics that manifests itself as copies of the original signal on the left and right of the signal.

SILLY HINT: Waterfalls are vertical. Too much water goes over the side.

https://3.bp.blogspot.com/-W14Qrvpj8gI/TsV1LrdpA8I/AAAAAAAAAG0/zwSQ3siYEs0/s1600/Splatter+2.JPG

The signal near 2050Hz shows this effect. Notice the copies of the signal.

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Check out WebSDR to see waterfall displays in action.

Notice that you can move the cursor horizontally along the x-axis in order to select the frequency, and that the display "falls" vertically over time. In other words: the x-axis is frequency, the y-axis is time.

You'll see a whole bunch of different signals. The CW signals will be very narrow, the data signals will tend to be quite wide, and phone signals somewhere in-between. If the signal is good, the display will show a bright line. A more attenuated line indicates that the signal isn't as strong. In other words: strength is intensity.

It is often advantageous to monitor the strength and frequency of multiple signals over a short duration of time. A waterfall display accomplishes just this.

If you've ever dealt with a spectrum analyzer, spectrogram, or a Fourier transform of a signal, you should notice that the horizontal axis of all the above plots is frequency. A waterfall plot adopts this convention.

(Silly tip: In a waterfall, water FALLS as time goes by).

(Also, try this: A body of water typically runs horizontally, then vertically down a falls with greater intensity).

(Another tip: Frequency Horizontal+Signal Intensity+Time Vertical) = FH+SI+TV = Fuzzy TV)

(Sily tip: A waterfall is vertical. The last word in the correct answer is "vertical")

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Silly Hint: Winlink is the only answer that is not capitalized.

Winlink is a project that is linking communication between the internet and amateur radio. The winlink network is managed by volunteers.

For more info see Wikipedia: Winlink

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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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