Spark Gap Tubes, Trigger Tubes & Passives

This section is a catch-all for simple vacuum and gas-filled devices used in relay and passive applications.

Bomac JAN-CBNQ-724B
 Bomac JAN-CBNQ-724B

Devices included in this entry:

Bomac JAN-CBNQ-724B TR cell
Sylvania 724B (pictured in thumbnail)


The 724B is a TR cell, a device used to protect the receiver portion of a microwave transceiver which shares the same antenna for both transmit and receive functions. A TR cell functions like a triggered gap tube, and blocks the receiver hardware by shorting the receiver input during transmitter operation. Transmitter pulses cause the spark gap to break down, shorting the receiver input.

The 724B was used in several WWII-era 10GHz mobile radar systems, including the AN/APS-1, ASD (AN/APS-3) ASH (AN/APS-4) and AN/MPG-1.

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Bomac BL-693
 Bomac BL-693

The Bomac BL-693 is a TR cell doped with the beta emitter Co-60. The initial radioactivity at the time of manufacture was rated at 11.1 kBq, but at the time of this writing has decayed to approximately 10 Bq. The initial Co-60 content of the BL-693 was 0.00000000025g, most of which has now been converted into stable Ni-60.

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Bomac BL11 / 6282
 Bomac BL11 / 6282

The Bomac BL11 / 6282 is a small cobalt-doped K-band TR cell with an operating frequency range of 23.6 to 24.6GHz.

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Bomac BLA-009
 Bomac BLA-009

TR cell doped with Co-60.

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C.P. Clare XG-1288
 C.P. Clare XG-1288

The C.P. Clare XG-1288 is an unusual, large cermet spark gap tube of unknown specification.

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Eimac CIM-481274
 Eimac CIM-481274

The Eimac CIM-481274 is a typical vacuum capacitor of unknown specification, though it appears to be extremely similar to the Eimac VC50-32, a 32kV, 50pF device. Portions of the CIM-481274's envelope are doped with uranium.

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General Electric GL-6452
 General Electric GL-6452

The General Electric GL-6452 is a microwave reference cavity, probably the simplest type of vacuum device in existence. Reference cavities are little more than a vacuum enclosed in a metal box with two glass apertures, and perform the function of stabilizing the output frequency of magnetrons and other microwave sources. The GL-6452 operates in the X-band range, 9.35GHz.

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General Electric Co. VI507
 General Electric Co. VI507

The General Electric Co. (GEC) VI507 is an argon-mercury spark gap tube used as a TR cell in Great Britain's second-generation AMES Type 2 metric radar network. The VI507 is rated for several hundred hours of operation at 25kW.

A note of disambiguation, GEC should not be confused with the US company General Electric (GE).

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WE / GE 8047
 WE / GE 8047

The Western Electric (manufactured by GE) 8047 is a small, fairly typical vacuum capacitor. The device is rated at 50 pF, 5kV@5A.

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