The Alpha 87A
Typically robust Alpha RF power Section (A) uses two Eimac 3CX800A7 triodes in grounded-grid. Blower floats on foam for quiet cooling. Plate pi-L network has silver-plated heavy tubing main coil, 80-160M coil on grooved ceramic form, and toroid L coil for low cross-coupling.
Split-stator capacitors permit precise tuning and maximum efficiency at higher frequencies. Dual plate RF chokes allow optimum efficiency across the full frequency range. Nine separate pretuned input networks assure low input VSWR on all HF amateur bands* and most MARS frequencies.
Power supply (B) uses massive tape-wound Hipersil(R) transformer like the ALPHA 77Dx's, banks of matched, full-size computer-grade filter capacitors. Full-wave bridge rectifier optimizes transformer efficiency and HV regulation.
Microprocessor-based controller (C) performs scores of functions, including counting the incoming drive frequency to insure that the ALPHA 87A's band and tuning are always correct. Whenever bandchange is required, in less than one second the control system automatically by-passes exciter power to the antenna, changes bands and retunes, and switches the amplifier back in-line! Manual tune and AlphaMAX auto-tune, your choice.
The controller is packaged on a 6-layer circuit board which saves space and efficiently decouples digital, analog, and power distribution circuits. Microprocessor and EPROM sockets permit easy software upgrades if/as they become available.
Display section (D) provides bright, color-coded LED bargraphs for full-time monitoring of peak RF forward and reflected power plus grid current. A fourth display is shared by less frequently used tune assist, plate current, and HV functions. All displays are easily readable from 10-15 feet.
Front panel push buttons (E) make it simple to field-program tuning and loading in five segments across each band. LED codes also identify any protective trip out which occurs.