GR-874

General Radio 874 (GR-874) Connectors are hermaphroditic (asexual) coaxial RF connectors developed by Eduard Karplus, Harold M. Wilson and William R. Thurston at General Radio in the late 1940s, initially "for applications up to 4500 Mc" (4.5 GHz).

They first appeared in Catalog L (1948). The original versions were friction-supported, in Catalog Q (1961) a locking series was introduced.

GR-874 connectors are carefully engineered to keep a constant impedance throughout the signal path, by varying conductor 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.

Different versions of the connector have different maximum voltage ratings; 1000 V is typical.

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 1-GHz Oscilloscope uses a 125 Ω GR-874 variant.

Many GR instruments came with GR-874 connectors standard. A large variety of adapters to other coax connector standards was available that allowed the end user to configure their instruments according to their interconnection needs.

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

From Arthur E. Thiessen, A History of the General Radio Company (1965):

Also, in 1948, after field tests and demonstrations lasting two years, the unique Type 874 coaxial connectors were announced. These were a joint development by Karplus, Harold M. Wilson (M. I. T. '31), and William R. Thurston (M. I. T. '43). A feature of the unique design is that any two connectors fit smoothly together without the usual complication of matching male and female assemblies. This feature, together with excellent electrical and mechanical performance, made them an immediate success. It is not known exactly how many of them are in use today in all their forms, but the number is in the millions.

Links

• GR-874 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
• 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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  50 Ω vs 75 Ω GR-874 connectors

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  GR-874 connectors on a Tektronix 106 Pulse Generator (1966)

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  Drawings from US Patent 2548457

GR-874 Series Coax Components

Product	Description	Introduced In
874-B	Coaxial connector	1948
874-C	Cable Connector	1948
874-P	Panel Connector	1948
874-PC	874-PC panel connector and cap	1948
874-Q2	874 to binding post adapter	1948
874-Q7	874 to 774 coax adapter	1948
874-C8	Cable Connector	1951
874-D20	Adjustable Stub	1951
874-EL	Coax right angle adapter	1951
874-G10	3.16× coax attenuator	1951
874-G20	10× coax attenuator	1951
874-GA	Adjustable Attenuator	1951
874-JR	Coax rotary joint	1951
874-K	Coaxial coupling capacitor	1951
874-L10	10cm airline	1951
874-L20	20cm airline	1951
874-L30	30cm airline	1951
874-MR	Mixer Rectifier	1951
874-T	874 coax tee	1951
874-VR	Voltmeter rectifier	1951
874-WM	874 50 Ω terminator	1951
874-WN	874 short-circuit termination	1951
874-WO	874 open-circuit termination	1951
874-P58	Panel Connector	1954
874-P8	Panel Connector	1954
874-QBJ	874 to BNC jack adapter	1954
874-QBP	874 to BNC plug adapter	1954
874-QCJ	874 to C jack coax adapter	1954
874-QCP	874 to C plug coax adapter	1954
874-QHJ	874 to HN jack coax adapter	1954
874-QHP	874 to HN plug coax adapter	1954
874-QNJ	874 to N jack coax adapter	1954
874-QNP	874 to N plug coax adapter	1954
874-QUJ	874 to UHF jack adapter	1954
874-QUP	874 to UHF plug adapter	1954
874-VC	Variable Capacitor	1954
874-X	Coax insertion unit	1954
874-G3	1.4× coax attenuator	1956
874-G6	2× coax attenuator	1956
874-LBA	Slotted Line	1956
874-LV	Micrometer Vernier Attachment for Slotted Line	1956
874-QLJ	874 to HL (LC) jack coax adapter	1956
874-QLP	874 to HL (LC) plug coax adapter	1956
874-VQ	Voltmeter detector	1956
874-W100	874 100 Ω coax standard	1956
1607-P2	Coax tee	1959
874-QTNJ	874 to TNC jack coax adapter	1959
874-QTNP	874 to TNC plug coax adapter	1959
874-L10L	10cm airline	1961
874-QBJL	874 to BNC jack adapter	1961
874-QUJL	874 to UHF jack adapter	1961
874-TO58	Crimping Tool	1961
874-TO8	Crimping Tool	1961
874-TOK	Tool Kit	1961
874-C8A	Cable Connector	1963
874-G10L	3.16× coax attenuator	1963
874-G6L	2× coax attenuator	1963
874-L20L	20cm airline	1963
874-L30L	30cm airline	1963
874-M	Coax component mount	1963
874-ML	Coax locking component mount	1963
874-MRL	Mixer Rectifier Locking	1963
874-R20LA	Patch Cord	1963
874-R22LA	Patch Cord	1963
874-TL	874 coax tee	1963
874-VQL	Voltmeter detector	1963
874-QMMJ	874 to SMA jack coax adapter	1965
874-QMMP	874 to SMA plug coax adapter	1965
874-TPD	Resistive power divider	1965
874-TPDL	Resistive power divider	1965
874-U	Coax right angle adapter	1965
874-W50B	874 50 Ω terminator	1965
874-W50BL	874 50 Ω terminator	1965
874-G14	5× coax attenuator	1968
874-G14L	5× coax attenuator	1968
874-QUPL	874 to UHF plug adapter	?