In a vacuum tube, the transit time of electron between cathode and anode is important at

A Klystron is a vacuum tube used for generation/amplification of microwaves.

An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode.

This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher.

As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle.

Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation.

The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam.

The input is fed at buncher cavity and output is taken at catcher cavity.

In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used.

The features of a multicavity klystron are :

1. Frequency range - 0.25 GHz to 100 GHz

2. Power output - 10 kW to several hundred kW

3. Power gain - 60 dB (nominal value)

4. Efficiency - about 40%.

A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.

When a line is short-circuited at far end, the voltage at far end is zero.

A branched duplexer funds use in narrow bandwidth applications.

TR tube stands for transmit-receive tube and ATR tube stands for antitransmit receive tube.

Both these tubes are used in branched duplexer.

TE₀₁ mode is unaffected because its horizontally oriented electric field is every where perpendicular to the conducting strips.

Wavelength should be less than cutoff wavelengths.

Therefore frequency should be higher than cutoff frequency for minimum attenuation.

Same antenna is used for transmission and reception.

A parallel tuned circuit has an infinite impedance if R is zero.

A quarter wave line short-circuited at far end behaves as a parallel tuned circuit.

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As frequency increases, transmission loss increases slightly.