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General Radio 1604-B
Comparison bridge
General Radio 1604-B Comparison Bridge

Available from 1954 to 1956

Catalog History
 Document Year Page
Catalog N 1954 93
Catalog O 1956 31
(All manuals in PDF format unless noted otherwise)

The General Radio 1604-B Comparison Bridge was introduced in Catalog N (1954) and remained available through Catalog O (1956).

It was designed for sorting, adjusting and comparing two devices at three different frequencies.

Impedance difference can be measured in two ranges, 5% or 20%, selected by a front panel switch, using a built-in generator and detector equipped with a 2AP1 CRT. Balance is achieved when the vertical deflection is at a minimum.

Dissipation factor difference is read directly from the dial in one range. The main change from the 1604-A is the addition of a 400 Hz test frequency.


  • Deviation Range: Impedance difference, ±5% and ±20%, switched. Dissipation factor difference, ±0.006 at 400 Hz, ±0.015 at 1 kHz, ±0.075 at 5 kHz
  • Test Frequency: 400 Hz, 1 kHz, or 5 kHz within ±3%
  • Voltage Applied to Unknown: Approximately 1 V for impedances above 500 Ω, decreasing for lower values of impedance