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One of the reasons why vacuum tubes eventually fail at microwave frequencies is that their

One of the reasons why vacuum tubes eventually fail at microwave frequencies is that their Correct Answer Noise figure increases

For vacuum tubes, the noise figure increases as the frequency of operation increases. Thus, at microwave frequencies, vacuum tubes eventually fail to provide minimum required SNR.

Related Questions

Which of the following statements are correct? 1. A lowpass filter passes low frequencies and stops high frequencies. 2. A highpass filter passes high frequencies and rejects low frequencies 3. A bandpass filter passes frequencies within a frequency band and attenuates frequencies outside the band. 4. A bandstop filter passes frequencies within the band and blocks/attenuates frequencies outside a frequency band.
Study the table carefully to answer the question that follows   Schools CLASSES VI VII VIII IX X   Pass Fail Pass Fail Pass Fail Pass Fail Pass Fail A 84 12 56 12 82 9 80 14 86 12 B 56 18 64 16 88 7 64 11 73 12 C 53 16 60 10 58 12 63 9 63 18 D 62 11 62 14 64 13 61 7 53 17 E 70 15 76 17 78 10 52 13 79 1 F 58 8 72 13 72 14 45 12 75 11 What is the average number of fail students from class IX from all the schools together?
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Among the five objects, Gas stove, Washing machine, Refrigerator, Inverter and Microwave oven: the Washing machine is twice as heavy as the Inverter; the Gas stove is one and half time as heavy as the Microwave oven; the Washing machine and Microwave oven together weigh as much as the Gas stove and Inverter together; the Refrigerator and Inverter together are one and half times as heavy as the Gas stove. Which is the heaviest among the five objects?
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Microwave tubes are power sources themselves at higher frequencies and can be used independently without any other devices.
Resistors used at normal operating frequencies can be directly used at microwave frequencies in MMIc.
Given below are two premises with four conclusions drawn from them. Which of the following conclusions could be validity drawn from the premises? Premises: (i) All fans are tubes (ii) Bulbs are not tubes Conclusions: (A) Fans are not bulbs (B) All tubes are fans (C) Fans are bulbs (D) No tube is bulb Select the correct answer from the options given below: