165003HB Radar Display Tube

The 165003HB (also designated as the 1650/03HB) is a 16-inch diameter radar display tube designed for professional radar applications. Manufactured by Ferranti, this cathode-ray tube features a metal-backed screen, magnetic deflection, and low-voltage electrostatic focusing. It is designed to provide high-resolution displays with a nominal deflection angle of approximately 50 degrees.

Screen and Phosphor Characteristics

The 165003HB is equipped with a specialized Type "H" phosphor screen. This screen configuration is characterized by:

• Fluorescence: Orange
• Afterglow: Orange
• Persistence: Very Long

Due to the nature of the Type "H" phosphor material, the screen is highly sensitive to thermal and beam-intensity damage. It is liable to burn if operated with a stationary or slow-moving spot, even when the beam current is kept at low values.

A closely related variant, the 1650/03JB, shares the same physical and electrical structure but utilizes a Type "J" phosphor screen, which exhibits blue fluorescence, a yellow afterglow, and long persistence.

Physical Specifications and Basing

The tube is constructed with a glass envelope featuring a nominal diameter of 406 mm and a maximum overall length of 600 mm. It utilizes a standard B12A (Duodecal) base and a CT8 Cavity Type anode cap.

Dimensional Tolerances

• Overall Diameter: 406 ± 4 mm
• Overall Length: 600 ± 10 mm
• Neck Diameter: 35 ± 0.5 mm
• Reference Line Diameter: 36 mm
• Distance from Reference Line to Faceplate Edge: 380 ± 5 mm
• Distance from Cavity Cap to Faceplate Edge: 290 ± 10 mm
• Faceplate Spherical Radius: 700 mm

Mounting and External Coating

The 165003HB can be mounted in any position except vertically with the screen facing downwards. The tube is manufactured with an external conductive coating. This coating, when combined with the internal anode structure, forms a capacitance of approximately 1500 pF, which can be utilized for Extra High Tension (E.H.T.) smoothing.

Pin Connections

The B12A base connections, viewed from the underside, are allocated as follows:

Electrical Ratings and Operating Conditions

The 165003HB operates with an indirectly heated cathode requiring a nominal heater supply of 6.3 V at 0.3 A.

Absolute Maximum and Minimum Ratings

To ensure reliable operation and prevent damage, the following limits must be observed:

• Maximum First Anode ($A_1$) Voltage: 500 V
• Minimum First Anode ($A_1$) Voltage: 200 V
• Maximum Combined Second and Fourth Anode ($A_2 + A_4$) Voltage: 18 kV
• Minimum Combined Second and Fourth Anode ($A_2 + A_4$) Voltage: 8 kV
• Maximum Positive Third Anode ($A_3$) Voltage: +500 V
• Maximum Negative Third Anode ($A_3$) Voltage: -500 V
• Maximum Heater-to-Cathode Voltage ($V_{h-k}$): 200 V
• Maximum Grid-to-Cathode Resistance ($R_{g-k}$): 1.5 MΩ
• Maximum Heater-to-Cathode Resistance ($R_{h-k}$): 1.0 MΩ

Typical Operating Points

Under typical operating conditions, the tube is configured with the following parameters:

• Heater Voltage: 6.3 V
• First Anode ($A_1$) Voltage: 300 V
• Second and Fourth Anode ($A_2 + A_4$) Voltage: 15 kV
• Third Anode ($A_3$) Voltage (for Focus): -300 V to +300 V
• Grid Voltage ($V_g$) for Visual Cut-off: -40 V to -100 V

Modulator Operating Constraints

The modulator (grid) must never be allowed to become positive with respect to the cathode during normal operation. The only exception is immediately after switching off the equipment, at which point the grid voltage may be permitted to rise to a maximum of +1 V.

Deflection, Shielding, and Capacitances

The 165003HB employs magnetic deflection with a nominal deflection angle of 50 degrees.

Magnetic Shielding Requirements

When external static shift coils are used in conjunction with the main deflecting system, the neck and lens regions of the tube must be carefully shielded from fringe magnetic fields. Failure to provide adequate shielding will result in deflection de-focusing.

Interelectrode Capacitances

• Cathode to all other electrodes ($C_{k-all}$): 8 pF
• Grid to all other electrodes ($C_{g-all}$): 8 pF
• Anode to external conductive coating ($C_{a-ext. coating}$): Approximately 1500 pF

Technical Summary

The 165003HB is a specialized 16-inch radar display tube featuring a metal-backed screen with a very long persistence Type "H" orange phosphor. It utilizes low-voltage electrostatic focusing and 50-degree magnetic deflection. Operating with a 6.3 V, 0.3 A heater, the tube requires a typical high-voltage supply of 15 kV on its combined second and fourth anodes, with a focusing range of -300 V to +300 V on the third anode. Housed in a glass envelope with a B12A Duodecal base and a CT8 cavity cap, it is designed for precise radar display systems where long-persistence tracking is required, provided that precautions against screen burn and magnetic fringe fields are strictly maintained.