This particular tube was obtained in the fall of 2003. The Varian 4K3SJ is a  4-Cavity CW Klystron with  integral permanent magnet focusing rated at 1.0 kW out for the  1.7 -to- 2.4 Ghz. band. The required filament supply is 6.0 Volts  at 4 -to- 5 Amps (which is at the Gun Voltage potential of - 6 kV since  the collector and tube body are at “ground”). When operated at the recommended Gun Voltage of  - 6 KV, the nominal Beam Current is 0.65 Amps.


RF input is by way of a female “N” connector, the output is a standard EIA 1&5/8 rigid coax female flange connection. Gain at nominal operating voltage is 45 dB with an expected power output of 1.0 Kilowatt.   


 Upon arrival, I performed several tests to determine the operational status of  the tube. RF test were conducted on both input and output cavities "cold". I conducted Hi-Pot tests and gas tests up to 7 kV, but I did not have a 6 kV beam power supply or a filament power supply with enough isolation to operate the tube at full Beam power. As of 20 Nov 2005, the Beam power supply is still under construction. In order to test the tube for acceptance I performed measurements of the tube perveance at voltages up to – 1 Kv. The plot below is the resulting Beam Current vs. Voltage curve. Since perveance is a good test of gun alignment, a "predicted" curve of perveance, below, can be compared against a plot of a perveance of 2E-6. Since I do not have a measurement from a known good tube or data from Varian; 2E-6 has been estimated from the reccomended operating point for 1 kW output.

So far,this tube looks good !

Measured Perveance of the Klystron


Predicted Perveance of the Klystron assuming standard 2 “microPervs”


Extrapolation of the Measured Perveance Curve to 5 Kv

(extending the plot of a third order fit of data measured up to 1 Kv)


Varian tube specifications  and more details of the the step-by-step procedures I employed to test for gas, emission and cold RF tuning as well as my associated notes can be found here.


    Please note that the information included in this page is changing and that statements by the author are presented without warranty…   i.e.  your mileage may vary. Whenever possible I have indicated the source of information presented.


                                                                                              - Kermit Carlson  W9XA     20 November 2005