3 1-19.   With a sine-wave input, how will the output compare to the input in (a) a linear circuit and (b) a nonlinear circuit? 1.  (a) Proportional (b) proportional 2.  (a) Proportional (b) not proportional 3.  (a) Not proportional (b) not proportional 4.  (a) Not proportional (b) proportional 1-20.   What effect, if any, does a nonlinear device have on a sine wave? 1.  It amplifies without distortion 2.  It attenuates without distortion 3.  It generates harmonic frequencies 4.  None 1-21.   For the heterodyning action to occur in a circuit, (a) what number of frequencies must be present and (b) to what type of circuit must they be applied? 1.  (a) Two (b) linear 2.  (a) Two (b) nonlinear 3.  (a) Three (b) nonlinear 4.  (a) Three (b) linear 1-22.   Spectrum analysis is used to view which of the following characteristics of an rf signal? 1.  Phase 2.  Bandwidth 3.  Modulating wave 4.  Modulation envelope 1-23.   The method of rf communication that uses either the presence or absence of a carrier in a prearranged code is what type of modulation? 1.  Pulse modulation 2.  Amplitude modulation 3.  Continuous-wave modulation 4.  Pulse-time modulation 1-24.   What is the purpose of the key in a cw transmitter? 1.  It generates the rf oscillations 2.  It heterodynes the rf oscillations 3.  It controls the rf output 4.  It amplifies the rf signal 1-25.   To ensure frequency stability in a cw transmitter, you should NOT key what circuit? 1.  The mixer 2.  The detector 3.  The oscillator 4.  The rf amplifier 1-26.   When keying a high-power transmitter, what component should you use to reduce the shock hazard? 1.  A coil 2.  A relay 3.  A resistor 4.  A capacitor 1-27.   Interference detected by a receiver is often caused by the application and removal of power in nearby transmitters.   This interference can be prevented by using what type of circuit in such transmitters? 1.  Power filter 2.  On-off filter 3.  Key-click filter 4.  Rf detector filter 1-28.   Transmitter machine keying was developed for which of the following purposes? 1.  To increase the speed of communications 2.  To make communications more intelligible 3.  To reduce interference 4.  Each of the above