The ALPHA 77Dx (type accepted model PA-77DF and government/export model PA-77Dx)* is a high power HF linear amplifier of exceptional quality, ruggedness, and sophisticated design. It is much smaller than other amplifiers of comparable capability, yet provides greater operational versatility, cooler operation, and a lower acoustical noise level than much larger and heavier units. Unique design features of the ALPHA 7?Dx include ETO's exclusive full-cabinet ducted air cooling system, built-in CW break-in keying system, frequency coverage down to 1.8 MHz, and a highly efficient custom power transformer using a tape-wound core of grainoriented silicon steel. High efficiency of operation is maintained across the tuning range by a combination of vacuum variable output tuning capacitor and ETO's expertly designed mixture of silver plated, heavy copper tubing coils and multi-insulated, toroidal inductors.