Modulation 51-100

• Bandwidth is the width of frequencies within the spectrum occupied by a signal and used by the signal for conveying information
• H3E transmits only one sideband
• Continuous modulation is a kind of modulation in which the modulated wave is always present
• Pulse modulation is a type of modulation in which no signal is present between pulses
• The coefficient of modulation describes the amount of amplitude change present in an AM waveform
• Carrier shift is a form of amplitude distortion introduced when the positive and negative alternations in the AM modulated signals are not equal
• The advantage of phase modulation over direct FM frequency modulation is that the oscillator is crystal-controlled
• Frequency translation is when the spectrum is shifted in frequency with no other changes
• A balanced modulator is a device capable of causing frequency translation
• Frequency translation or upconversion is when the frequency of each component in a signal spectrum is increased by the same fixed amount
• Any device to be used as a frequency multiplier must be nonlinear
• A push-push amplifier circuit is used for frequency doubling
• Frequency division is useful in the implementation of a frequency synthesizer
• Frequency division by 12 will require 4 flip-flops in the counter
• A balanced modulator can be used as a phase detector
• An indirect frequency synthesizer contains only a single crystal
• A recognizable feature of a CW transmitter is a keyed transmitter, power amplification, and frequency generation
• The term "pulling" refers to the change of the crystal oscillator frequency by loading
• Indirect FM is achieved when frequency modulation is achieved by initial phase modulation
• A disadvantage of direct FM is the need for AFC
• Direct FM can be achieved by a reactance tube modulator or a varactor diode
• A TRF receiver is a receiver in which all RF amplifier stages require manual tuning to the desired RF
• Amplifier stages are often necessary before the demodulator in a receiver to amplify weak antenna signals
• A serious disadvantage of the TRF receiver is bandwidth variations over the tuning range
• A modulator is not a part of a superheterodyne receiver
• An RF amplifier will not be found in every superheterodyne receiver
• The mixer, a major element of a superheterodyne receiver, must be nonlinear
• The change of the modulated carrier frequency from the original RF to the IF of the superheterodyne receiver is known as frequency translation
• The key to achieving receiver sensitivity is the reduction of internal noise
• Reduction of receiver internal noise is not an impossible receiver design objective
• The S/N ratio for the output of a receiver is smaller than the S/N ratio for the input
• The noise figure specifies the self-generated noise of a receiver
• The image rejection ratio is the ratio of the superheterodyne receiver response at the desired carrier frequency to that at the image frequency
• The core of an IF transformer usually contains powdered iron
• Shape factor is a measure of skirt steepness
• AGC is the function that tends to maintain the sound volume level of a voice receiver nearly constant for a large signal strength range
• Squelch is the function that tends to silence the receiver in the absence of transmitted carrier
• A noise blanker is incorporated in a communications receiver to reduce impulse noise
• SBB voice is the type of signal in which a receiver selectivity of 2.4 kHz in the I-F circuitry is optimum
• If the input to a detector stage is an amplitude-modulated (A3E) IF signal, then the output from the stage is audio voice information