W4CA

Roanoke Valley Amateur Radio Club

T-8

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Subelement T8

Modulation modes, non-voice communication and operating activities.

 

Single sideband is a form of amplitude modulation. FM is most commonly used for VHF packet radio transmissions. SSB is most often used for long-distance (weak signal) contacts on the VHF and UHF bands. FM is most commonly used for VHF and UHF voice repeaters. Upper sideband is normally used for 10 meter HF, VHF and UHF single-sideband communications. CW has the narrowest bandwidth. SSB signals have narrower bandwidth is the primary advantage of single sideband over FM for voice transmissions. 3 kHz is the approximate bandwidth of a single sideband voice signal. Between 10 and 15 kHz is the approximate bandwidth of a VHF repeater FM phone signal. About 6 MHz is the typical bandwidth of analog fast-scan TV transmissions on the 70 cm band. 150 Hz is the approximate maximum bandwidth required to transmit a CW signal.

 

Any amateur whose license privileges allow them to transmit on the satellite uplink frequency may be the control operator of a station communicating through an amateur satellite or space station. Use minimum amount of power needed to complete the contact on the uplink frequency of an amateur satellite or space station. Maps showing the real-time position of the satellite track over the earth, the time, azimuth, and elevation of the start, maximum altitude, and end of a pass and the apparent frequency of the satellite transmission, including effects of Doppler shift are provided by satellite tracking programs. Any amateur holding a Technician or higher-class license may make contact with an amateur station on the International Space Station using 2 meter and 70 cm band amateur radio frequencies. A transmission from a space station that contains information about a satellite is a satellite beacon. The Keplerian elements are inputs to a satellite-tracking program. An observed change in signal frequency caused by relative motion between the satellite and the earth station is Doppler shift. The satellite uplink is in the 70 cm band and the downlink is in the 2-meter band is operating in mode U/V. Rotation of the satellite and its antennas causes spin fading when referring to satellite signals. Initials LEO tell you the satellite is in a Low Earth Orbit. FM Packet is a commonly used method of sending signals to and from a digital satellite.

 

 

Radio direction finding is used to locate sources of noise interference or jamming. A directional antenna would be useful for a hidden transmitter hunt

 

Contesting is a popular operating activity involving contacting as many stations as possible during a specified period of time. Send only the minimum information needed for proper identification and the contest exchange is good procedure when contacting another station in a radio contest. A letter-number designator assigned to a geographic location is a grid locator.

 

1 watt is the maximum power allowed when transmitting telecommand signals to radio controlled models. A label indicating the licensee’s name, call sign and address must be affixed to the transmitter in place of on-air station identification when sending signals to a radio control model using amateur frequencies.

 

A method of delivering voice communications over the Internet using digital techniques is Voice Over Internet Protocol (VoIP) as used in amateur radio. You can obtain a list of active nodes that use VoIP from a repeater directory. Use the keypad to transmit the IRLP node ID to select a specific IRLP node when using a portable transceiver. By using DTMF signals is how you access to an IRLP node. A gateway is the name given to an amateur radio station that is used to connect other amateur stations to the Internet. A technique to connect amateur radio systems, such as repeaters, via the Internet using Voice Over Internet Protocol is the Internet Radio Linking Project (IRLP).

 

Packet, PSK31 and MFSK are examples of digital communications. Automatic Packet Reporting System is “APRS”. A Global Positioning System receiver provides data to the transmitter when sending automatic position reports from a mobile amateur radio station. Providing real time tactical digital communications in conjunction with a map showing the locations of stations is an application of APRS (Automatic Packet Reporting System). PSK is Phase Shift Keying. A low-rate data transmission mode is PSK31.

 

Check sum which permits error detection, a header which contains the call sign of the station to which the information is being sent and automatic repeat request in case of error are included in packet transmissions.

 

International Morse is used when sending CW in the amateur bands. Straight Key, Electronic Keyer and Computer Keyboard can be used to transmit CW in the amateur bands.

 

A digital scheme where by the receiving station detects errors and sends a request to the sending station to retransmit the information is an ARQ transmission system.

An analog fast scan color TV signal is indicated by the term NTSC.

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SUBELEMENT T8

Modulation modes: amateur satellite operation; operating activities;

non-voice and digital communications

[4 Exam Questions – 4 Groups]

Which of the following is a form of amplitude modulation?

  1. Single sideband

What type of modulation is most commonly used for VHF packet radio transmissions?

  1. FM

Which type of voice mode is most often used for long-distance (weak signal) contacts on the VHF and UHF bands?

  1. SSB

Which type of modulation is most commonly used for VHF and UHF voice repeaters?

  1. FM

Which of the following types of emission has the narrowest bandwidth?

  1. CW

Which sideband is normally used for 10 meter HF, VHF, and UHF single-sideband communications?

  1. Upper sideband

What is an advantage of single sideband (SSB) over FM for voice transmissions?

  1. SSB signals have narrower bandwidth

What is the approximate bandwidth of a single sideband (SSB) voice signal?

  1. 3 kHz

What is the approximate bandwidth of a VHF repeater FM phone signal?

  1. Between 10 and 15 kHz

What is the typical bandwidth of analog fast-scan TV transmissions on the 70 centimeter band?

  1. About 6 MHz

What is the approximate maximum bandwidth required to transmit a CW signal?

  1. 150 Hz

What telemetry information is typically transmitted by satellite beacons?

  1. Health and status of the satellite

What is the impact of using too much effective radiated power on a satellite uplink?

  1. Blocking access by other users

Which of the following are provided by satellite tracking programs?

Maps showing the real-time position of the satellite track over the earth, the time, azimuth,and elevation of the start, maximum altitude, and end of a pass and the apparent frequency of the satellite transmission, including effects of Doppler shift.

 

What mode of transmission is used for satellite beacons?

RTTY, CW and Packet

What is a satellite beacon?

  1. A transmission from a satellite that contains status information

Which of the following are inputs to a satellite tracking program?

  1. The Keplerian elements

With regard to satellite communications, what is Doppler shift?

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

What is meant by the statement that a satellite is operating in mode U/V?

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

What causes spin fading of satellite signals?

  1. Rotation of the satellite and its antennas

What do the initials LEO tell you about an amateur satellite?

  1. The satellite is in a Low Earth Orbit

Who may receive telemetry from a space station?
A. Anyone who can receive the telemetry signal

Which of the following is a good way to judge whether your uplink power is neither too low nor too high?

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

Which of the following methods is used to locate sources of noise interference or jamming?

  1. Radio direction finding

Which of these items would be useful for a hidden transmitter hunt?

  1. A directional antenna

What operating activity involves contacting as many stations as possible during a specified period?

  1. Contesting

Which of the following is good procedure when contacting another station in a radio contest?

  1. Send only the minimum information needed for proper identification and the contest exchange

What is a grid locator?

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

How is access to some IRLP nodes accomplished?

  1. By using DTMF signals

What is meant by Voice Over Internet Protocol (VoIP) as used in amateur radio?

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

What is the Internet Radio Linking Project (IRLP)?

  1. A technique to connect amateur radio systems, such as repeaters, via the internet using Voice Over Internet Protocol (VoIP)

How might you obtain a list of active nodes that use VoIP?

By subscribing to an on line service, From on line repeater lists maintained by the local repeater frequency coordinator, or From a repeater directory

What must be done before you may use the Echolink system to communicate using a repeater?
D. You must register your call sign and provide proof of license

What name is given to an amateur radio station that is used to connect other amateur stations to the internet?

  1. A gateway

Which of the following is a digital communications mode?

  1. Packet radio, IEEE 802.11 and JT65

What does the term “APRS” mean?

  1. Automatic Packet Reporting System

Which of the following devices is used to provide data to the transmitter when sending automatic position reports from a mobile amateur radio station?

  1. A Global Positioning System receiver

What type of transmission is indicated by the term “NTSC?”

  1. An analog fast scan color TV signal

Which of the following is an application of APRS (Automatic Packet Reporting System)?

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

What does the abbreviation “PSK” mean?

  1. Phase Shift Keying

Which of the following best describes DMR (Digital Mobile Radio or Digital Migration Radio)?

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

Which of the following may be included in packet transmissions?

A check sum that permits error detection, A header that contains the call sign of the station to which the information is being sent and Automatic repeat request in case of error

What code is used when sending CW in the amateur bands?

  1. International Morse

Which of the following operating activities is supported by digital mode software in the WSJT suite?
Moonbounce or Earth-Moon-Earth, Weak-signal propagation beacons and Meteor scatter

What is an ARQ transmission system?

  1. A digital scheme whereby the receiving station detects errors and sends a request to the sending station to retransmit the information

Which of the following best describes Broadband-Hamnet(TM), also referred to as a high-speed multi-media network?

  1. An amateur-radio-based data network using commercial Wi-Fi gear with modified firmware

What is FT8?

  1. A digital mode capable of operating in low signal-to-noise conditions that transmits on 15-second intervals

What is an electronic keyer?

  1. A device that assists in manual sending of Morse code

 

 

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