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 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, 0.1, 0.01, 0.001, and 0.0001 times the RMS Voltmeter reading
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Noise tube, V2, operating in magnetic field
