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Subelement T8
Modulation modes: amateur satellite operation; operating activities; non-voice communications
Section T8D
Non-voice communications: image signals; digital modes; CW; packet; PSK31; APRS; error detection and correction; NTSC
Which of the following is an example of a digital communications method?
  • Packet
  • PSK31
  • MFSK
  • Correct Answer
    All of 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.

The methods listed here are all digital modes:

  • Packet Radio is probably the best known digital mode which can be thought of as using a modem over a radio to allow computers to exchange data

  • JT65 is a digital protocol developed for amateur radio communication with extremely weak signals. It was designed by Joe Taylor, K1JT, to optimize Earth-Moon-Earth (EME) contacts on the VHF bands. The "65" refers to the 65 tones the protocol uses.

  • PSK31 is short for Phase Shift Keying, 31 Baud and is more of system for chat over radio; it allows realtime keyboard to keyboard informal chat between operators.

  • MFSK is short for Multiple frequency-shift keying and is a variation of FSK, a method used by some packet radio systems.

  • IEEE 802.11 is a set of specifications for implementing wireless local area network (WLAN) computer communication in the 900 MHz and 2.4, 3.6, 5, and 60 GHz frequency bands.

Last edited by mk2019. Register to edit

Tags: digital modes arrl chapter 5 arrl module 11

What does the term "APRS" mean?
  • Correct Answer
    Automatic Packet Reporting System
  • Associated Public Radio Station
  • Auto Planning Radio Set-up
  • Advanced Polar Radio System

APRS, Automatic Packet Reporting System, is a standard utilizing packet radio and a GPS to send beacons with the location of the unit. There are many things you can do with APRS, but many use it on bicycles to track their progress, on their vehicle to track where it is, etc. There have even been reports of APRS- equipped vehicles being stolen and then quickly tracked down thanks to the APRS unit.

Last edited by kd7bbc. Register to edit

Tags: digital modes definitions arrl chapter 5 arrl module 11

Which of the following devices provides data to the transmitter when sending automatic position reports from a mobile amateur radio station?
  • The vehicle speedometer
  • A WWV receiver
  • A connection to a broadcast FM sub-carrier receiver
  • Correct Answer
    A Global Positioning System receiver

Automatic location reports need to know the location to automatically report; thus, they use a GPS just like anything else would =]

If you think about this one, it couldn't be the speedometer anyway; that would only tell you how fast you are going. (also APRS, Automatic Position Reporting System, can be used when biking, driving, walking, etc all just as easily as the other). The other two options are just random things thrown in hoping you won't know what they are so you'll guess wrong. Nearly everyone knows what a GPS is, so this shouldn't be hard to remember.

Last edited by bdengle32@yahoo.com. Register to edit

Tags: digital modes arrl chapter 5 arrl module 11

What type of transmission is indicated by the term NTSC?
  • A Normal Transmission mode in Static Circuit
  • A special mode for earth satellite uplink
  • Correct Answer
    An analog fast scan color TV signal
  • A frame compression scheme for TV signals

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, NTSC stands for Never 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

Last edited by gusgus45. Register to edit

Tags: amateur television (atv) arrl chapter 6 arrl module 14

Which of the following is an application of APRS (Automatic Packet Reporting System)?
  • Correct Answer
    Providing real time tactical digital communications in conjunction with a map showing the locations of stations
  • Showing automatically the number of packets transmitted via PACTOR during a specific time interval
  • Providing voice over Internet connection between repeaters
  • Providing information on the number of stations signed into a repeater

It helps to know what APRS is and does. It transmits a station's GPS coordinates, so other stations can locate it. The components are a GPS receiver, a ham radio transmitter, and some logic to connect the two so the transmitter sends out the GPS coordinates. So:

It has nothing to do with counting packets, It doesn't require voice over Internet, and It doesn't count stations connected to a repeater.

It just provides real time communications that gives your location. In conjunction with a map, it shows your location to the stations that receive your GPS coordinates via the APRS system.

Last edited by avabelle. Register to edit

Tags: arrl chapter 5 arrl module 11

What does the abbreviation PSK mean?
  • Pulse Shift Keying
  • Correct Answer
    Phase Shift Keying
  • Packet Short Keying
  • Phased Slide Keying

Phase Shift Keying is a method for digitally transmitting data (with a computer of some sort) by varying (keying) the phase of the signal.

Phase refers to where you are in the cycle -- the peaks and valleys of the sine wave

Last edited by kd7bbc. Register to edit

Tags: digital modes definitions arrl chapter 5 arrl module 11

What is PSK31?
  • A high-rate data transmission mode
  • A method of reducing noise interference to FM signals
  • A method of compressing digital television signals
  • Correct Answer
    A low-rate data transmission mode

PSK31 stands for Phase Shift Keying, 31 baud. PSK31 is one of the simplest data modes available; to someone listening, it sounds almost like an electronic whistle, but in actuality it alternates between two phases (hence the name). PSK31 is a fairly slow (low-rate) digital mode and is used mostly for information text chat between two amateur radio operators.

Think of a slow instant messaging system that runs over the radio.

Last edited by bdengle32@yahoo.com. Register to edit

Tags: definitions digital modes arrl chapter 5 arrl module 11

Which of the following may be included in packet transmissions?
  • A check sum which permits error detection
  • A header which contains the call sign of the station to which the information is being sent
  • Automatic repeat request in case of error
  • Correct Answer
    All of 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.

Last edited by bdengle32@yahoo.com. Register to edit

Tags: digital modes arrl chapter 5 arrl module 11

What code is used when sending CW in the amateur bands?
  • Baudot
  • Hamming
  • Correct Answer
    International Morse
  • Gray

CW stands for "Continuous Wave", which is a sine wave: an electromagnetic wave of constant amplitude and frequency.

This wave can be interrupted, creating an "off" state. The on and off states can be used to transmit Morse code.

The original version of Morse code developed by Samuel Morse is often referred to as Railroad Morse code or American Morse code—American because the rest of the world adopted International Morse. Eventually International Morse also replaced Railroad Morse in America, and this is what we use today.

The term CW comes up a lot; whether you remember what CW stands for or not, every amateur radio operator should know that CW means Morse code.

Last edited by rlaska. Register to edit

Tags: morse code arrl chapter 5 arrl module 11

Which of the following can be used to transmit CW in the amateur bands?
  • Straight Key
  • Electronic Keyer
  • Computer Keyboard
  • Correct Answer
    All of these choices are correct

CW is morse code. There are no restrictions on how you send the morse code, as long as it is correct international morse code.

Last edited by kd7bbc. Register to edit

Tags: morse code arrl chapter 5 arrl module 11

What is an ARQ transmission system?
  • A special transmission format limited to video signals
  • A system used to encrypt command signals to an amateur radio satellite
  • Correct Answer
    A digital scheme whereby the receiving station detects errors and sends a request to the sending station to retransmit the information
  • A method of compressing the data in a message so more information can be sent in a shorter time

ARQ stands for Automatic Repeat reQuest

When the receiving station detects an error, it automatically sends a repeat request to 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.

Last edited by happyday_kt. Register to edit

Tags: arrl chapter 5 arrl module 11

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