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microwave MOD Frequency & DIP Frequency

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Full Member level 3
Oct 24, 2009
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I have setup one Microwave testbench as shown in figure.

Modulation (MOD) frequency knob of Microwave source is been set at
mid position. Now the Frequency Meter reads a DIP Frequency of 9.34 GHz.

From Reflex Klystron MODE Study it is evident that- for all maximum
output power points, the DIP value will be same irrespective of repeller voltage.

Can I change DIP Frequency by

1. Changing MOD Frequency Knob position ?
2. Replacing Klystron Supply with Gunn Supply ?
What are the factors that decides DIP Vlaue ?
What is the difference between MOD & DIP Frequencies ?


If I understand correctly, you frequency-modulate the signal generator (klystron), and observe the dip at the frequency to which you set the wavemeter resonator.
To change the dip frequency, you should set the wavemeter to that frequency. If this dip frequency (absorption by wavemeter resonator) is out of the spectrum generated by the signal generator, you will not be able to see the dip.
Adjusting the MOD knob sets the modulation voltage which sweeps the signal frequency ; the center of the sweep spectrum is determined by repeller voltage. The repeller voltage also affects the signal output power, as well as the klystron cavity tuning.
I would not believe anyone still operates a 2K25 klystron... I donated all my klystrons to friends 30 years ago...:))
Thanks jiripolivka

In short , when DIP occurs
MOD Frequency= DIP Frequency
Is it correct ?

I do not think so!
Modulation frequency is a low frequency by which the signal frequency is modulated. The signal frequency is ~ 9.5 GHz for a 2K25 tube, and the DIP frequency is that one indicated by the scale on the wavemeter resonator.
Modulation frequency can be ~50 Hz, or, up to several MHz. Modulation VOLTAGE is superimposed to the repeller voltage, and forces the signal frequency to sweep, or change around ~9.5 GHz, say +/- 100 MHz while the sweep frequency means how fast this sweeping occurs.
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