Downloaded from https://www.everyspec.com MIL-STD-1311D 4.8.12 Multiunit tubes. In multiunit tubes the unit or units not under test shall be connected to the reference point or biased to cutoff. 4.8.13 Frequency/Wavelength conversion. Conversion between frequency and wavelength shall be made using the value c = 2.998 x 10 8 m/sec. 4.8.14 Reference point. All voltages are given with respect to the reference point as defined in Appendix A of MIL-PRF-1. 4.9 Microwave tube test setup instructions and precautions. The following precautions and instructions for operating microwave tubes apply to the tests specified herein: a.
Mount and ground the tube securely, connect (1) the high voltage, (2) the heater supply and other tube components, such as grids, focus electrodes, soles, accelerators, collectors, and repellers, (3) the rf output load system, (4) the rf drive connection, if an amplifier, to the tube under test (TUT), and (5) external magnets or solenoids when required. b. Provide the specified cooling through all cooling systems. c. Turn on pressurizing and activate arc detectors when needed. d. Turn on the heater supply in such a manner that the rated maximum heater current is not exceeded. (Some heater systems allow snap-on of the heater by use of inherent current limitation.) e.
Turn on magnetic field supply and adjust as required. f. The electrode to be grounded may be either the cathode or the anode. (See the TSS for proper connections.) However, it is common to operate the cathode below ground with the anode and collector at ground, although some collectors may be depressed in potential toward cathode potential. The cathode is the reference point for voltages. The operating currents and voltages are indicated on each individual tube, accompanying data sheet, or TSS. g. Application of voltages: (1) Tubes without control electrodes (magnetrons, some traveling-wave tubes, klystrons, etc):
Turn on input power as stated on the TSS and adjust to operate the tube at the specified value of the indicated parameter. Unless abrupt application of voltage is specifically required, it is preferable to raise the voltage (cw or pulse) slowly, especially if the tube has been inoperative or in storage for a few months. (2) Tubes with control electrodes: (a) If the specified control electrode voltage is positive relative to the cathode, turn on all other voltages first in any desired sequence.
(b) If the control electrode is negative with respect to the cathode, the beam control electrode voltage should first be biased to cutoff beam current at the desired operating condition, then apply other voltages approximately simultaneously. (c) Adjust the control electrode voltage until the required cathode current is reached. (d) If required by the TSS, program the heater input downward to compensate for backheating. (e) Removal of voltages may be simultaneous or in the reverse order of application. For some high-power tubes, it may be necessary to program removal of the magnetic field and cooling to follow removal of tube voltages.
(f) Upon completion of testing, liquid cooling (if used), shall be completely drained, and all protective covers shall be attached. h. Frequency meter accuracy: (1) Frequency meters for measuring tunable tubes operating at frequencies less than 30 GHz shall be calibrated to an accuracy of 0.1 percent. (2) Frequency meters for measuring fixed-tuned tubes operating at frequencies less than 30 GHz shall be calibrated to an accuracy of 0.05 percent. (3) Frequency meters for measuring tubes operating at frequencies of 30 GHz, or higher, shall be calibrated to an accuracy of 0.2 percent. 5