Description of a 144 MHz high power amplifier for 2 x 4CX250B     LA0BY, last updated 16.09.2000     View of anode circuit

This page provides information on the design and practical implementation of an inexpensive 144 MHz high power amplifier using a pair of ceramic tetrodes, type 4CX250B, in a push-pull configuration. The amplifier has been built in many variations. I have used it mainly for MS and EME operation for many years.

Important design features and measured operating parameters are displayed in the manual (WfW 2.0, 21 kB). The schematic diagrams were originally drawn by Designer 3.1. In order to make them come out independently, the drawings were exported into GIF and JPEG format. Those may be imported into Word documents and printed with reasonable, but not perfect quality.

 Schematic diagrams
 Switching and metering circuits: GIF 13 kB, JPEG 57 kB
 Mains power wiring and connectors: GIF 15 kB, JPEG 68 kB
 Power supply circuits: GIF 14 kB, JPEG 69 kB
 RF circuit: GIF 11 kB, JPEG 44 kB
 Equipment configuration for EME, including sequencing: GIF 14 kB, JPEG 71 kB
 Whole set of drawings as ZIP-file: Compressed GIF 64 kB, Compressed JPEG 205 kB

Pictures of power supply unit
 Front, rear and top (open chassis) view 
 Close up of HV circuit 
 Close up of grid/screen supply

Pictures of RF unit
 Front and rear view
 Anode compartment
 Close up of output circuit 
 Grid/cathode compartment 
 Close up of valve sockets and neutralising capacitors 
 Close up of grid circuit