144 MHz 1.2 Kilowatt Amplifier
Constructing a 1.2 kW 144 MHz amplifier using the GU74b tetrode for EME operations.
Description
A 144 MHz kilowatt amplifier project details the construction and performance of a high-power VHF linear using the GU74b tetrode. This Russian tube, equivalent to the Svetlana 4CX800, is noted for its conservative datasheet ratings, performing closer to 800-1000W anode dissipation in practical applications. The design prioritizes compactness and achieves 1.2 kW output with only 20W of drive power, demonstrating a 70% efficiency at 2.5 kV plate voltage. The amplifier has been successfully deployed in demanding EME (Earth-Moon-Earth) operations since June 1994.
Challenges encountered during development included achieving stability with a grid-1 input configuration. The author, CT1DMK, opted not to publish the full design due to its complexity, suggesting it might be difficult for less experienced builders to replicate successfully. However, he invites direct contact for those with specific interest in the design.
Future plans include a "144MHz GS35b compact amplifier" project, promising another kilowatt-plus design. This resource offers insights into high-power VHF amplifier construction and the practical application of specific power tubes.