1390-B

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

The Type 1390-B provides random noise on three ranges from 20 kHz to 5 MHz. It produces electrical noise 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 then of the noise signal before it is fed to a five position decade attenuator at the output.

Specifications

• Frequency Range: 5 Hz to 5 MHz in three bands.
• 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, .1, .01, .001, and .0001 times the RMS Voltmeter reading.

Links

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

Photos

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  Noise tube, V2, operating in magnetic field