This amplifier build using GU-74B tetrode, which is used in wideband nontunable amplifiers and for single-sideband power amplification in stationary and mobile RF equipment. It is useful at full ratings through 250MHz. The GU-74b tetrode is generally considered to be similar to the 4CX800A, although some users report that it acts more like a tube having 900 or 1000W anode dissipation. For more information see http://www.ok1rr.com/tubes/gu74b.pdf.
This PA has input 25-30 Watt, and gives output up to 650 Watt.