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
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
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.