New Zealand NZART pool, section ZLJ30

Subelement ZLJ

Digital Systems

Section ZLJ30

Digital Systems

ZLJ3001

In the block diagram shown, the block designated "modem" is a

Correct Answer
A.
modulator/demodulator
B.
modulation emphasis unit
C.
Morse demodulator
D.
MOSFET de-emphasis unit

ZLJ3001

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ZLJ3002

In the block diagram shown, the "modem"

A.
monitors the demodulated signals
B.
de-emphasises the modulated data
Correct Answer
C.
translates digital signals to and from audio signals
D.
determines the modulation protocol

ZLJ3002

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ZLJ3003

The following can be adapted for use as a modem

A.
an electronic keyer
B.
a spare transceiver
C.
a spare receiver
Correct Answer
D.
a computer sound-card

ZLJ3003

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ZLJ3004

The following are three digital communication modes

A.
DSBSC, PACTOR, NBFM
B.
AGC, FSK, Clover
C.
PSK31, AFC, PSSN
Correct Answer
D.
AMTOR, PACTOR, PSK31

ZLJ3004

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ZLJ3005

In digital communications, FSK stands for

A.
phase selection keying
B.
final section keying
Correct Answer
C.
frequency shift keying
D.
final signal keying

ZLJ3005

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ZLJ3006

In digital communications, BPSK stands for

Correct Answer
A.
binary phase shift keying
B.
baseband polarity shift keying
C.
band pass selective keying
D.
burst pulse signal keying

ZLJ3006

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ZLJ3007

When your HF digital transmission is received with errors due to multi-path conditions, you should

A.
increase transmitter power
Correct Answer
B.
reduce transmitted baud rate
C.
reduce transmitter power
D.
change frequency slightly

ZLJ3007

For the receiving end to be able to accurately decode the characters sent, the bits must be sent at a constant speed. The signalling speed of serial data transmissions on wires is measured in bits per second (bps), since the bits are always sent one at a time. However, the signalling speed on a radio link is not measured in bits, but in symbols per second (the unit of symbols/sec is the baud). The symbol is the basic modulated signalling entity on a radio link, and represents the state of each signalling interval. Each symbol may carry one or more (or even less) data bits, depending on the modulation technique. For RTTY, each symbol (a short duration of one tone or another) carries one data bit, so the speed in bps is the same as the baud rate.

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ZLJ3008

The letters BBS stand for

A.
binary baud system
Correct Answer
B.
bulletin board system
C.
basic binary selector
D.
broadcast band stopper

ZLJ3008

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ZLJ3009

APRS is an adaptation of packet radio. APRS stands for

Correct Answer
A.
Automatic Packet Reporting System
B.
Amateur Position Reporting System
C.
Automatic Packet Relay System
D.
Amateur Position Relay System

ZLJ3009

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ZLJ3010

The following communication mode is generally used for connecting to a VHF packet radio bulletin board

A.
SSB
B.
AM
Correct Answer
C.
FM
D.
DSB

ZLJ3010

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