What is reactance modulator in FM?

A reactance modulator changes the frequency of the tank circuit of the oscillator by changing its reactance. This is accomplished by a combination of a resistor, a condenser, and a vacuum tube (the modulator) connected across the tank circuit of the oscillator as in Fig.

What is the reactance modulator?

The reactance modulator gets the modulating signal as input. It operates on the tank circuit of an LC master oscillator. The output of this oscillator is FM signal. It is passed through a buffer and amplitude limiter before it is applied to the Class C power amplifier.

What are the different methods of FM generation?

Methods of FM Generation.

How do you generate FM using phase modulator?

FM signals can be generated either by using direct frequency modulation, which is achieved by inputting a message directly into a voltage-controlled oscillator, or by using indirect frequency modulation, which is achieved by integrating a message signal to generate a phase-modulated signal, which is then used to …

How is a reactance modulator used in FM generation?

Reactance Modulator In direct FM generation, the instantaneous frequency of the carrier is changed directly in proportion with the message signal. For this, a device called voltage controlled oscillator (VCO) is used. A VCO can be implemented by using a sinusoidal oscillator with a tuned circuit having a high value of Q.

What are the different types of frequency modulation?

The frequency modulation methods of producing frequency modulation may be put under two broad categories: A direct method of producing frequency modulation uses an electron device such as an electron, BJT, FET or varactor diode which itself behaves as a voltage variable reactance, either capacitive or inductive.

How is frequency modulation achieved in direct FM?

Frequency modulation can also be achieved from voltage controlled devices such as P IN diode, Klystron oscillators and multivibrators. In direct FM generation, the instantaneous frequency of the carrier is changed directly in proportion with the message signal. For this, a device called voltage controlled oscillator (VCO) is used.

How is a reactance tube used in frequency modulation?

However, today it has been almost replaced by methods using semiconductor devices. By reactance tube is meant an electron tube which offers between anode and cathode terminals a reactance varying in accordance with the modulation voltage applied between its control grid and cathode.