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This is the classic RF Power tetrode valve for VHF and low UHF applications. The base is a special because it has to incorporate the air system, a matching ceramic chimney was made for the base, and the control grid was connected to the central metal spigot.

We have the co-axial version in the museum as well as similar types. The anode to outer ring is filled with folded ribbon for a large surface area and this is clearly visible. All external metalwork is silver plated.

We have an example of the glass based 4X150A in the museum, this is almost identical but has a lower power rating.

Thanks to Graham, G3XTZ for providing details of the correct heater voltage, and to Derek G3GRO for providing this exhibit.

The co-axial envelope is 41 mm in diameter and, excluding the B8F base pins, is 45 mm tall.

References: Data-sheet & G3XTC. Type 4CX250FG was first introduced in 1960. See also 1960 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.