Amateur Radio Signals MODULATION MODES SIGNAL BANDWIDTH DIGITAL

Amateur Radio Signals MODULATION MODES, SIGNAL BANDWIDTH, DIGITAL MODES: PACKET, PSK 31

Modulation modes, signal bandwidth �When you get your Technician license, chances are FM is the type of modulation that you’ll use first. Frequency modulation, or FM, is the type of modulation most commonly used for VHF and UHF voice repeaters. (T 8 A 04) �FM is also the type of modulation most commonly used for VHF packet radio transmissions. (T 8 A 02)

FM Signal

Modulation modes, signal bandwidth �Single sideband, or SSB, is the type of voice modulation most often used for long-distance or weak signal contacts on the VHF and UHF bands. (T 8 A 03) �Single sideband is a form of amplitude modulation. (T 8 A 01) A single-sideband signal may be upper- or lower -sideband. �Upper sideband is normally used for 10 meter HF, VHF and UHF single-sideband communications. (T 8 A 06)

Single Sideband Signal

Modulation modes, signal bandwidth �The primary advantage of single sideband over FM for voice transmissions is that SSB signals have narrower bandwidth. (T 8 A 07) �The approximate bandwidth of a single sideband voice signal is 3 k. Hz. (T 8 A 08) �The approximate bandwidth of a VHF repeater FM phone signal is between 10 and 15 k. Hz. (T 8 A 09)

Modulation modes, signal bandwidth �Morse Code, or CW, is the type of emission that has the narrowest bandwidth. (T 8 A 05) �The approximate maximum bandwidth required to transmit a CW signal is 150 Hz. (T 8 A 11) � International Morse is the code used when sending CW in the amateur bands. (T 8 D 09)

Modulation modes, signal bandwidth Technicians have CW privileges on the 80 m, 40 m, 15 m, and 10 m bands, as well as all the VHF, UHF, and microwave bands. An electronic keyer is a device that assists in manual sending of Morse code. (T 8 D 14)

Modulation modes, signal bandwidth �WSJT software is software that provides weak-signal digital communication modes on amateur radio frequencies. To communicate with one of the digital modes that WSJT software provides, you need a single sideband transceiver and a personal computer with a sound card. Which of the following operating activities is supported by digital mode software in the WSJT suite? All of these choices are correct (T 8 D 10): Moonbounce or Earth-Moon-Earth Weak-signal propagation beacons Meteor scatter

Modulation modes, signal bandwidth

Modulation modes, signal bandwidth �Some modes have very wide bandwidths. The typical bandwidth of analog fast-scan TV transmissions on the 70 cm band, for example, is about 6 MHz. (T 8 A 10) �The type of transmission indicated by the term NTSC is an analog fast scan color TV signal. (T 8 D 04)

Digital modes: packet, PSK 31 �When hams talk about “digital modes, ” we are talking about modes that send digital data rather than voice or other types of analog signals, such as television. Usually, we connect our transceivers to a computer to modulate and demodulate the digital signals, but some newer transceivers can do this internally. All of these choices are correct (examples of a digital communications method) (T 8 D 01): • Packet radio • IEEE 802. 11 • JT 65

Digital modes: packet, PSK 31 �Packet radio was one of the first digital modes. It is called packet radio because the data to be sent from station to station is separated into a number of packets which are then sent separately by the transmitting station and received and re-assembled by the receiving station. All of these choices are correct when talking about what may be included in a packet transmission (T 8 D 08): • 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

Digital modes: packet, PSK 31 �Some amateur radio digital communications systems use protocols which ensure error-free communications. One such system is called an automatic repeat request, or ARQ, transmission system. An ARQ transmission system is a digital scheme whereby the receiving station detects errors and sends a request to the sending station to retransmit the information. (T 8 D 11)

Digital modes: packet, PSK 31 �APRS is one service that uses packet radio. The term APRS means Automatic Packet Reporting System. (T 8 D 02) A Global Positioning System receiver is normally used when sending automatic location reports via amateur radio. (T 8 D 03) 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). (T 8 D 05) �http: //aprs. fi

Digital modes: packet, PSK 31 �A popular digital mode on the HF bands is PSK. The abbreviation PSK means Phase Shift Keying. (T 8 D 06)

Digital modes: packet, PSK 31 �Digital Mobile Radio, or DMR, is an FM digital communications system that’s become quite popular in amateur radio. It allows amateur radio operators to use the spectrum more efciently by multiplexing two signals in a single 12. 5 k. Hz repeater channel. It also allows amateur radio operators to connect with one another over the internet. �DMR (Digital Mobile Radio) is best described as a technique for time-multiplexing two digital voice signals on a single 12. 5 k. Hz repeater channel. (T 8 D 07)