% FILENAME = N20.TXT
% Harmonics and Parasitics 
% Release version 2, January 00

%QUESTION: 1
#20.1 A harmonic of a signal transmitted at 3525 kHz would be expected to occur at: 

3573 kHz 

7050 kHz 

14025 kHz 

21050 kHz 

% ans 2 

%QUESTION: 2 
#20.2 The third harmonic of 7 MHz is: 

10 MHz 

14 MHz 

21 MHz 

28 MHz 

% ans 3 

%QUESTION: 3 
#20.3 The fifth harmonic of 7 MHz is: 

12 MHz 

19 MHz 

28 MHz 

35 MHz 

% ans 4 

%QUESTION: 4 
#20.4 Excessive harmonic output may be produced in a transmitter by: 

a linear amplifier 

a low SWR 

resonant circuits 

overdriven amplifier stages 

% ans 4  

%QUESTION: 5 
#20.5 Harmonics may be produced in the RF power amplifier of a transmitter if: 

the modulation level is too low 

the modulation level is too high 

the oscillator frequency is unstable 

modulation is applied to more than one stage 

% ans 2 

%QUESTION: 6 
#20.6 Harmonics produced in an early stage of a transmitter may be reduced in a later stage by: 

increasing the signal input to the final stage 

using FET power amplifiers 

using tuned circuit coupling between stages 

using larger value coupling capacitors 

% ans 3 

%QUESTION: 7 
#20.7 Harmonics are produced when: 

a resonant circuit is detuned 

negative feedback is applied to an amplifier 

a transistor is biased for class A operation 

a sine wave is distorted 

% ans 4 

%QUESTION: 8 
#20.8 Harmonic frequencies are: 

always lower in frequency than the fundamental frequency 

at multiples of the fundamental frequency 

any unwanted frequency above the fundamental frequency 

any frequency causing TVI 

% ans 2 

%QUESTION: 9 
#20.9 An interfering signal from a transmitter has a frequency of 57 MHz. This signal could be the: 

seventh harmonic of an 80 meter transmission 

third harmonic of a 15 metre transmission 

second harmonic of a 10 metre transmission 

crystal oscillator operating on its fundamental 

% ans 3 

%QUESTION: 10 
#20.10 To minimise the radiation of one particular harmonic, one can use a: 

wave trap in the transmitter output 

resistor 

high pass filter in the transmitter output 

filter in the receiver lead 

% ans 1 

%QUESTION: 11 
#20.11 A low-pass filter is used in the antenna lead from a transmitter: 

to reduce key clicks developed in a CW transmitter 

to increase harmonic radiation 

to eliminate chirp in CW transmissions 

to reduce radiation of harmonics 

% ans 4 

%QUESTION: 12 
#20.12 The following is installed in the transmission line as close as possible to a HF transmitter to reduce harmonic output: 

a middle-pass filter 

a low-pass filter 

a high-pass filter 

a band-reject filter 

% ans 2 

%QUESTION: 13 
#20.13 A low pass filter will: 

suppress sub-harmonics 

reduce harmonics 

always eliminate interference 

improve harmonic radiation 

% ans 2 

%QUESTION: 14 
#20.14 A spurious transmission from a transmitter is: 

an unwanted emission unrelated to the output signal frequency 

an unwanted emission that is harmonically related to the modulating audio frequency 

generated at 50 Hz 

the main part of the modulated carrier 

% ans 1 

%QUESTION: 15 
#20.15 A parasitic oscillation: 

is an unwanted signal developed in a transmitter 

is generated by parasitic elements of a Yagi beam 

does not cause any radio interference 

is produced in a transmitter oscillator stage 

% ans 1 

%QUESTION: 16 
#20.16 Parasitic oscillations in a RF power amplifier can be suppressed by: 

pulsing the supply voltage  

placing suitable chokes, ferrite beads or resistors within the amplifier 

screening all input leads  

using split-stator tuning capacitors   

% ans 2 

%QUESTION: 17 
#20.17 Parasitic oscillations in the RF power amplifier stage of a transmitter may occur: 

at low frequencies only 

on harmonic frequencies 

at high frequencies only 

at high or low frequencies 

% ans 4 

%QUESTION: 18 
#20.18 Transmitter power amplifiers can generate parasitic oscillations on: 

the transmitter's output frequency 

harmonics of the transmitter's output frequency 

frequencies unrelated to the transmitter's output frequency 

VHF frequencies only 

% ans 3 

%QUESTION: 19 
#20.19 Parasitic oscillations tend to occur in: 

high voltage rectifiers 

high gain amplifier stages 

antenna matching circuits 

SWR bridges 

% ans 2 

%QUESTION: 20 
#20.20 Parasitic oscillations can cause interference. They are: 

always the same frequency as the mains supply 

always twice the operating frequency 

not related to the operating frequency 

three times the operating frequency 

% ans 3