% 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: 
<img src = "digista.gif" align = center width = 352 height = 93> 
<extralines = 1 totallines = 6 >

modulator/demodulator 

modulation emphasis unit 

Morse demodulator 

MOSFET de-emphasis unit 
 
% ans 1 

%QUESTION: 2
#30.2 In the block diagram shown, the "modem": 
<img src = "digista.gif" align = center width = 352 height = 93> 
<extralines = 1 totallines = 6 >

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 





