Tuning Procedures

Tuning MSDC Klystron Transmitters for Visual output:

Before getting started, put the transmitter into "STANDBY" mode and check for the following paramaters:

1) Heater Voltage is aproximately 7.0V at 17 A nominal (or factory specified setting)
2) Ion Pump (Getter) is aproximately 3.3KV at ZERO

3) Focus is set to aproximately 11 Amps nominal

4) Set Re-Focus to 7.25A nominal

5) Make SURE that you test all of the Safeties and Interlocks for proper operation before continuing.

Course Tuning Procedure: Before beginning normal tuning, perform the following on ALL Cavities

Turn the Tuning Knob FULLY counterclockwise until it comes to a stop
Make sure that the counter reads ZERO. If it doesn't, set it now and lock it down so it tunes properly. On Varian Transmitters, the counter is "gravity" centered. So you zero them with the cavity in an upright position, then lay the cavity on it's side (normal position).
Turn the knobs on ALL cavities till the counter reads 10 turns.

WARNING: If during tuning, the penultimate cavity EVER reaches the carrier resonant frequency - you can possibly destroy the tube.

(I highly suggest you don't let this happen.)

Normally, the penultimate cavity is tuned to be at least above the kept 6MHZ up from the carrier frequency.

Tuning Procedure: Once the course tuning is accomplished, and all the prerequisite voltage and current levels have been checked, you can begin the Klystron tuning as follows:

1) Tune the Ultimate Cavity (the driver) to Fc (frequency of the video carrier)

2) Tune the Penultimate Cavity to AT LEAST 8 MHz above Fc.

3) Tune the 2nd Cavity 1 1/2 MHZ below Fc

4) **** Tune 3rd Cavity (if it exists) to 4 MHz above Fc

**** Note: this is only done on 5 cavity klystron tubes. Disreguard this step on a 4 cavity tube.

5) Tune the 1st Cavity to 2MHz above Fc.

6) Raise the Beam Voltage to a normal level

7) Increase the Drive to normal

8) Adjust the Loading and Coupling of the cavities for slope and edge effects.
At this time we should look to make sure that the following guidelines are adhered to:

Anode Voltage is a low as necessary

Filiment Voltage is still at the factory specified setting (7.0V nom)

Tube Seal temperatures are low

Ion Pump is functioning, but not overworking

High Tube gain

Low VSWR

Bandwidth is just enough to do the job, yet be within FCC tolerances.

Total Currents add up to a nominal amount (3.5KA)

Just Sufficient Headroom

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This Course was written by Ray Dall © All Rights Reserved.
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