1B57 — Fixed-Tuned ATR Gas Switching Tube

The 1B57 is a fixed-tuned ATR (Anti-Transmit-Receive) gas switching tube designed for operation in the $S_a$ band. Sponsored by the Sperry Gyroscope Co., Inc., and registered under RMA Release Number 444 on October 5, 1945, this specialized microwave tube is designed for high-frequency radar and communication systems.

Electrical and RF Characteristics

The 1B57 is engineered to operate at a specific resonant frequency with defined electrical limits to ensure proper impedance matching and switching performance in waveguide or transmission line assemblies. Its primary electrical and radio-frequency characteristics include:

• Resonant Frequency: The tube is fixed-tuned to a nominal resonant frequency of 3325 Mc. (megacycles per second) with a tolerance of $\pm$ 1/2%. This precise tuning ensures optimal performance within its designated portion of the $S_a$ band.
• Loaded Q ($Q_L$): The maximum loaded quality factor ($Q_L$) is rated at 4.5. This relatively low Q-factor indicates a broad operating bandwidth around the resonant frequency, which is typical for gas switching devices of this class.
• Tuning Susceptance ($B/Y_0$): The normalized tuning susceptance is specified within a range of $\pm$ 0.05, ensuring minimal mismatch when integrated into the transmission system.
• Equivalent Conductance ($G/Y_0$): The maximum normalized equivalent conductance is 0.1, representing low insertion loss and high efficiency when the tube is in its non-operating or unfired state.
• Transmitter Peak Power: The tube is rated to handle a minimum transmitter peak power of 20 kW, making it suitable for high-power pulsed microwave applications.

Mechanical and Environmental Characteristics

The physical construction and environmental tolerances of the 1B57 are designed to withstand demanding operating conditions while maintaining stable electrical characteristics.

• Ionizable Medium: The tube utilizes Argon gas as its internal ionizable medium. When subjected to high-power RF energy from a transmitter, this gas ionizes to form a conductive path, facilitating the switching action.
• Mounting Position: The 1B57 can be operated in any permissible mounting position, offering flexibility in system layout and waveguide configuration.
• Environmental Limits: The device is rated for reliable operation across a wide ambient temperature range, spanning from -50 to +100 °C. This wide range ensures stability in extreme environmental conditions, such as those encountered in military or aerospace installations.
• Physical Dimensions and Mounting: The physical envelope of the tube includes 10-32 diameter mounting holes to facilitate secure mechanical attachment to the waveguide or system chassis.

Technical Summary

The 1B57 is a fixed-tuned $S_a$-band ATR gas switching tube containing an Argon ionizable medium. It is characterized by a resonant frequency of 3325 Mc. $imes$ 1/2%, a maximum loaded Q of 4.5, a tuning susceptance of $\pm$ 0.05, and a maximum equivalent conductance of 0.1. Capable of handling a minimum transmitter peak power of 20 kW, the tube is designed for versatile installation in any mounting position and is rated to operate across an ambient temperature range of -50 to +100 °C.