1390-B

The General Radio 1390-B is a random noise generator introduced in Catalog Q (1961) that remained available through Catalog 1978.

The Type 1390-B provides random noise on three ranges from 20 kHz to 5 MHz, produced using a 6D4 gas-discharge tube, V2, operated in the field of a permanent magnet. The noisy plate voltage of the 6D4 tube drives two stages of amplification. Between the amplifier stages, filter networks shape the three bands.

A voltmeter displays RMS voltage of the noise signal before it is fed to a five-position decade attenuator at the output.

Specifications

• Frequency Range: 5 Hz to 20 kHz, 500 kHz, or 5 MHz
• Output Voltage: 3 V for 20 kHz range, 2 V for 500 kHz range, and 1 V for 5 MHz range
• Output Impedance: 900 Ω
• Output Attenuator: 1, 0.1, 0.01, 0.001, and 0.0001 times the RMS Voltmeter reading

Links

• Experimenter December 1951 describing 1390-A
• Experimenter January 1960 describing 1390-B

Photos

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  Noise tube, V2, operating in magnetic field