GR-874 connector

General Radio 874 (GR-874) connectors are hermaphroditic (asexual) coaxial RF connectors developed by Eduard Karplus in the late 1940s, initially for applications up to "4500 Mc" (4.5 GHz).

GR-874 connectors are carefully engineered to keep a constant impedance throughout the signal path, by varying connector diameters between free-air and dielectrically supported sections. These connectors therefore exhibit very little reflection and are well suited for frequencies up to 9 GHz and pulse applications. For higher frequencies a smaller connector is required to avoid the excitation of wave guide modes.

Most GR-874 connectors came in 50 Ω impedance. Versions for 75 Ω and 125 Ω were also available using the same ground shield and housing, but different (thinner) center pin geometry. See for example the Tektronix 519 oscilloscope that had a 125 Ω GR-874 variant at the input.

Different versions of the connector have different maximum voltage ratings; 1000 V is typical. There are locking and non-locking versions.

By the 1970s, GR-874 connectors were being supplanted by SMA connectors in test equipment, also motivated by increasing bandwidth requirements.

GR-874 connectors and adapters continue to be available through IET Labs, Max-Gain Systems, Pasternack and possibly others.

The connector was also used by other manufacturers in the 1960s and 1970s, e.g. Tektronix (see https://w140.com/tekwiki/wiki/GR-874_connector), Hewlett-Packard, and Philips.

Links

• GR connector @ Wikipedia
• A Radically New Coaxial Connector for the Laboratory. General Radio Experimenter, Volume 23 No.5, October 1948
• New and Improved Coaxial Connectors. General Radio Experimenter, Volume 35 No.10, October 1961
• GR-874 Section of 1973 General Radio Catalog
• US Patent 2548457, Harold M Wilson, Coaxial connector for high-frequency transmission lines. Filed Jan. 10, 1947; Granted Apr. 10, 1951
• MGS sales list of GR874 hardware

Pictures

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  125 Ω GR-874 connector

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  Drawings from US Patent 2548457