Downloaded from https://www.everyspec.com MIL-STD-1311D METHOD 1341 POWER OUTPUT 1. Class A amplifier. Power output shall be measured with specified potentials applied to the tube. The specified signal shall be applied to the control grid and measurement made of the total power output delivered from the anode of the tube into the specified resistive load. Unless otherwise specified, the impedance of the signal source shall be very low as compared with the minimum peak grid impedance. For a change in power output with reduced filament or heater voltage, the reading at the reduced voltage shall be taken when the value of the power output is rising or stable. Precaution:
The impedance of all voltage supplies shall be limited to 1 percent of the load resistance. Where an anode coupling transformer or choke is used, the loss should be added to the power measured in the load resistance. 1.1 This test shall be made with the circuit shown on figure 1341-1. The specified load shall be inserted in the anode circuit, the specified potentials shall be applied to the tube elements, and an audio frequency sinusoidal voltage of specified value shall be applied directly to the control grid. The internal impedance of the signal source shall not exceed 2,500 ohms.
The rms alternating voltage across the load shall be measured with an rms measuring vacuum-tube voltmeter whose input impedance is at least 1 Meg, or with a current meter in series with the load, and the ac power in the load calculated. Meter: RMS values; Ch: Negligible dc resistance. C: Negligible reactance at the signal frequency. FIGURE 1341-1. Circuit for measuring class A power output. 2. Class B amplifier. This test shall be made on a tube or on each separate unit of multiunit tubes, in the circuit shown on figure 1341-2. The grid circuit shall have the specified impedance at the signal frequency and negligible dc resistance.
The grid signal shall be adjusted to the specified voltage without a tube in the socket. The impedance of the signal source shall be adjusted without a tube in the socket so that a resistor load of the same value as the specified impedance decreases the signal voltage 50 percent when connected across the grid circuit. The total harmonic distortion of the signal shall not exceed 5 percent excluding distortion introduced by the source impedance. A noninductive resistance load (R ) shall be inserted in the anode circuit of the tube without the use of shunting choke or transformer. The specified anode voltage (Eb) shall be regarded as supply voltage (Ebb) for this test.
The dc anode current shall be measured with no signal (Ibo) and with the specified signal (Ibs) and the power output calculated as follows: R Ibo Ibs Po 4 4 = π 2 2 METHOD 1341 1341-1 19 April 1968