Amrita Sai Institute of Science & Technology

Approved by AICTE, Permanently Affiliated to JNTU, KAKINADA

Accredited by NAAC with ‘A’ Grade
Paritala, Kanchikacherla (MD), Krishna (DT). AP, India – 521 180

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

Exp no:-01 ASIST

REFLEX KLYSTRON CHARACTERISTICS

Aim: To determine the following mode characteristics of reflex klystron.
(i) Repeller voltage vs relative o/p voltage.
(ii) Repeller voltage vs frequency of oscillation.

Equipment Required:
S.NO EQUIPMENT QUANTITY
1 CRO 1
2 klystron power supply 1
3 klystron mount 1
4 Isolator 1
5 Frequency meter 1
6 variables Attenuator 1
7 Detectors mount 1
8 VSWR meter 1
9 wave guide stand 1
10 BNC cable 1
11 cooling fan 1

Circuit Diagram:

SKPS
VSWR
METER
2K2S

KLYSTRON ISOLATOR FREQUENCY VARIABLE DETECTOR

ATTENUATOR
METER MOUNT
MOUNT

CRO

Theory:
The reflex klystron makes use of velocity modulation to transform a continuous electron
beam into microwave power. Electron emitted from the cathode are accelerated &passed through
the positive resonator towards negative reflector, which retards and, finally ,reflects electrons and
the electrons turn back through the resonator . suppose an RF-field exists between the
resonators the electrons travelling forward will be accelerated or retarted , as the voltage at
the resonator changes in amplitude. The accelerated electrons leave the resonator at an
increased velocity and the retarted electrons leave at the reduced velocity. The electrons leaving
the electrons leaving the resonator will need different time to return, due to change in velocities. As a
result, returning electrons group together in the bunches, as the bunches pass through resonator, they
interact with voltage at the resonator grids. If the bunches pass the grid at such a time that the electron
are slowed down by the voltage then energy will be delivered to the resonator and the klystron will
oscillate.

Procedure:
1. Connect the equipments and components as per the circuit diagram.
2. Set micrometer of variable attenuator around zero position.
3. Set the range switching of VSWR meter to 50db position, meter switch to normal position. Rotate
the frequency meter to one side fully.
4. Set mod-selector switch to AM-MOD position. Beam voltage control knob to the maximum clock
wise position. Reflector (repeller). Voltage control knob to the maximum clock wise position. And
meter switch to ‘off’ position.
5. Switch ‘on’ the klystron power supply, VSWR meter and cooling fan.
6. Change the meter switch of klystron power supply to beam voltage knob clockwise up to 300V
 Amrita Sai Institute of Science & Technology
Approved by AICTE, Permanently Affiliated to JNTU, KAKINADA
Accredited by NAAC with ‘A’ Grade
Paritala, Kanchikacherla (MD), Krishna (DT). AP, India – 521 180

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

7. Keep the AM-MOD amplitude knob and AM-FREQ at the mid position; connect the detector output
(BNC CABLE) to VSWR meter.
8. Rotate the reflector voltage knob to get deflection in VSWR meter.
9. Rotate the AM-MOD amplitude knob and AM-FREQ knob and also adjust the variable attenuators
to 10mm to get the maximum output in VSWR meter.
10. If necessary, change the range switch of VSWR meter 30db to50db if the deflection in VSWR
meter is out of scale or less than normal scale respectively
11. Remove the BNC cable from VSWR and connect it to C.R.O.
12. Set the Repeller voltage to the same value and note down the corresponding out put voltages
(square wave) from C.R.O, then start the rotating frequency meter slowly, at the same frequency
there will be oscillation is seen in the C.R.O, then it is the frequency of oscillation for the
particular repeller voltage.
13. Vary the repeller voltage in step and note down the corresponding o/p voltages and frequency
of oscillation in the same way explained in step no:-12.
14. Draw the graphs (i) repeller voltage vs o/p voltage. (ii) Repeller voltage vs frequency of
oscillation.

Record of observation:-
S. No Repeller voltage Repeller o/p voltage Frequency of
(in-volts) (in-volts) oscillations(in GHZ)
1 242
2 238

20 18

Model graph

Result: Thus the reflex klystron characteristic has been observed.