874-GA

The General Radio 874-GA Adjustable Attenuator was introduced in Catalog M (1951) and remained available through Catalog Q (1961).

The Type 874-GA is a mutual-inductance (waveguide-below-cutoff) type attenuator. A micrometer-type barrel adjusts the distance between a pick-up loop attached to a three-foot coaxial cable and the short section of the input coaxial line. Both the barrel and adjusting sleeve are calibrated in decibels, one turn produces a change of 20 dB for a total or 120 dB of attenuation. Used with other coaxial elements the such as the 874-VI Voltmeter Indicator or the 874-VR Voltmeter Rectifier, the 874-GA can be used to attenuate and monitor signal generators and oscillators. The attenuator can also be used to measure the attenuation of a network by the substitution method.

Specifications

• Calibrated Range: 120 dB
• Insertion Loss:
  • At beginning of calibrated range: Approximately inversely proportional to frequency up to 1 GHz; approximately 20 dB at 1 GHz with tuned input; approximately 33 dB with input line terminated in 50 Ω
  • Outside of calibrated range: Approximately inversely proportional to frequency; approximately 18 dB at 1 GHz
• Accuracy of Attenuation: ±0.5 dB when corrected
• Frequency Range: 100 MHz to 3 GHz
• Waveguide Mode: TE_1,1; cutoff frequency 12.3 GHz

Links

• Experimenter January 1950 describing Type 874-GA

Photos

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