% FILENAME N30.TXT
% Digital Systems
% Release version 3, October 2001
% Q 9 modified 6 Mar 2012
%QUESTION: 1
#30.1 
In the block diagram shown, the block designated "modem" is a:
modulator/demodulator
modulation emphasis unit
Morse demodulator
MOSFET de-emphasis unit
% ans 1
%QUESTION: 2
#30.2
In the block diagram shown, the "modem":
monitors the demodulated signals
de-emphasises the modulated data
translates digital signals to and from audio signals
determines the modulation protocol
% ans 3
%QUESTION: 3
#30.3 The following can be adapted for use as a modem:
an electronic keyer
a spare transceiver
a spare receiver
a computer sound-card
% ans 4
%QUESTION: 4
#30.4 The following are three digital communication modes:
DSBSC, PACTOR, NBFM
AGC, FSK, Clover
PSK31, AFC, PSSN
AMTOR, PACTOR, PSK31
% ans 4
%QUESTION: 5
#30.5 In digital communications, FSK stands for:
phase selection keying
final section keying
frequency shift keying
final signal keying
% ans 3
%QUESTION: 6
#30.6 In digital communications, BPSK stands for:
binary phase shift keying
baseband polarity shift keying
band pass selective keying
burst pulse signal keying
% ans 1
%QUESTION: 7
#30.7 When your HF digital transmission is received with errors due to multi-path
conditions, you should:
increase transmitter power
reduce transmitted baud rate
reduce transmitter power
change frequency slightly
% ans 2
%QUESTION: 8
#30.8 The letters BBS stand for:
binary baud system
bulletin board system
basic binary selector
broadcast band stopper
% ans 2
%QUESTION: 9
#30.9 APRS is an adaptation of packet radio. APRS stands for
Automatic Packet Reporting System
Amateur Position Reporting System
Automatic Packet Relay System
Amateur Position Relay System
% ans 1
%QUESTION: 10
#30.10 The following communication mode is generally used for connecting to a
VHF packet radio bulletin board:
SSB
AM
FM
DSB
% ans 3