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E4D01 What is meant by the blocking dynamic range of a receiver? / A. The difference in dB between the level of an incoming signal which will cause 1 dB of gain compression, and the level of the noise floor / B. The minimum difference in dB between the levels of two FM signals which will cause one signal to block the other / C. The difference in dB between the noise floor and the third order intercept point / D. The minimum difference in dB between two signals which produce third order intermodulation products greater than the noise floor
E4D02 Which of the following describes two types of problems caused by poor dynamic range in a communications receiver? / A. Cross modulation of the desired signal and desensitization from strong adjacent signals / B. Oscillator instability requiring frequent retuning, and loss of ability to recover the opposite sideband, should it be transmitted / C. Cross modulation of the desired signal and insufficient audio power to operate the speaker / D. Oscillator instability and severe audio distortion of all but the strongest received signals
E4D03 How can intermodulation interference between two repeaters occur? / A. When the repeaters are in close proximity and the signals cause feedback in one or both transmitter final amplifiers / B. When the repeaters are in close proximity and the signals mix in one or both transmitter final amplifiers / C. When the signals from the transmitters are reflected out of phase from airplanes passing overhead / D. When the signals from the transmitters are reflected in phase from airplanes passing overhead
E4D04 What is an effective way to reduce or eliminate intermodulation interference between two repeater transmitters operating in close proximity to one another? / A. By installing a band-pass filter in the feed line between the transmitter and receiver / B. By installing a properly terminated circulator at the output of the transmitter / C. By using a Class C final amplifier / D. By using a Class D final amplifier
E4D05 If a receiver tuned to 146.70 MHz receives an intermodulation-product signal whenever a nearby transmitter transmits on 146.52 MHz, what are the two most likely frequencies for the other interfering signal? / A. 146.34 MHz and 146.61 MHz / B. 146.88 MHz and 146.34 MHz / C. 146.10 MHz and 147.30 MHz / D. 73.35 MHz and 239.40 MHz
E4D06 If the signals of two transmitters mix together in one or both of their final amplifiers, and unwanted signals at the sum and difference frequencies of the original signals are generated, what is this called? / A. Amplifier desensitization / B. Neutralization / C. Adjacent channel interference / D. Intermodulation interference
E4D07 Which of the following describes the most significant effect of an off-frequency signal when it is causing cross-modulation interference to a desired signal? / A. A large increase in background noise / B. A reduction in apparent signal strength / C. The desired signal can no longer be heard / D. The off-frequency unwanted signal is heard in addition to the desired signal
E4D08 What causes intermodulation in an electronic circuit? / A. Too little gain / B. Lack of neutralization / C. Nonlinear circuits or devices / D. Positive feedback
E4D09 What is the purpose of the preselector in a communications receiver? / A. To store often-used frequencies / B. To provide a range of AGC time constants / C. To improve rejection of unwanted signals / D. To allow selection of the optimum RF amplifier device
E4D10 What does a third-order intercept level of 40 dBm mean with respect to receiver performance? / A. Signals less than 40 dBm will not generate audible third-order intermodulation products / B. The receiver can tolerate signals up to 40 dB above the noise floor without producing third-order intermodulation products / C. A pair of 40 dBm signals will theoretically generate the same output on the third order intermodulation frequency as on the input frequency / D. A pair of 1 mW input signals will produce a third-order intermodulation product which is 40 dB stronger than the input signal
E4D11 Why are third-order intermodulation products within a receiver of particular interest compared to other products? / A. The third-order product of two signals which are in the band is itself likely to be within the band / B. The third-order intercept is much higher than other orders / C. Third-order products are an indication of poor image rejection / D. Third-order intermodulation produces three products for every input signal
E4D12 What is the term for the reduction in receiver sensitivity caused by a strong signal near the received frequency? / A. Desensitization / B. Quieting / C. Cross-modulation interference / D. Squelch gain rollback
E4D13 Which of the following can cause receiver desensitization? / A. Audio gain adjusted too low / B. Strong adjacent-channel signals / C. Audio bias adjusted too high / D. Squelch gain adjusted too low
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