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ch2 - 29 Parasitic oscillations are higher frequency...

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23. Transistors offer non linear operation and provide amplication 24. Low level modulation in an AM transmitter, intelligence superimposed on the carrier; then the modulated waveform is amplified before reaching the antenna 25. High level modulation in an AM transmitter, intelligence superimposed on the carrier at the last point before the antenna 26. High level modulation allows extremely efficient amplification of the higher-powered carrier. Low level systems offer the most economical approach for low power transmitter. 27. Radio frequency amplifiers must be neutralized to cancel fed-back signals to suppress self-oscillation 28. Parasitic oscillations are undesirable. They prevent amplication from taking place and introduce distortion.
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Unformatted text preview: 29. Parasitic oscillations are higher frequency self-oscillations in RF amplifiers. 30. Self oscillation can occur at a tuned frequency or high frequency, when internal fed-back signal isn’t cancelled probability increases. 32. Class C provides an abrupt nonlinearity when the device switches on and off, allowing generation of the sum and difference frequencies. 33. The PIN diodes act as variable resistors when they are operated above 100MHz, when frequency is lower they act as regular diodes. When the modulating signal goes positive it increases the level of forward bias on the PIN diode. A negative modulating signal subtracts from the forward bias. PIN diodes are the only practical AM modulators for carriers above 100MHz....
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