GR-874 connector

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General Radio 874 (GR-874) connectors are hermaphroditic (asexual) coaxial RF connectors developed by Eduard Karplus at General Radio 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. The Tektronix 519 uses the 125 Ω GR-874 variant.

The regular 50 Ω version is used in the 1S1, 1S2, 3S1, 3S7, 3T7, 4S1, 4S2, 5T1, 5T1A, 5T3, 7M11, N, S-1, S-2, 106, 109, 110, 113, 191, 261, 280, 281, 282, R293, 661, P6025, P6032, P6051, 017-0086-00, 017-0088-00, 035-5031-00, 067-506, 067-0511-00, 067-0513-00, 067-0578-99, 067-0594-00, 067-0832-01, and possibly others.

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, see e.g. the progression from the S-1 to the S-4 sampling heads, also motivated by the higher bandwidth requirements.

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