WB2FCN SATELLITE STATION AMPLIFIERS 2 METER and 70 CM. (500W INPUT)
The Satellite station amplifiers here
run at an input of 500 watts. There
are (2) one on 2 meters and one on 70 cm.,
running on 2 meters a single 4CX250B,
and 70 cm. a single 4CX250K. The
4CX250K has a filament requirement
of 6.0 VAC but the 4X150G that came
in the original unit ran with 26 VAC,
and thus the change. These units were
purchased from FAIR RADIO SALES,
as an alternative to doing a lot of machining
to make the cavities for these bands.
The 2 meter amplifier is the model AM-912/GRC
module which was used in the T-302 transmitting set. The 70 cm
amplifier was from the AM-1178/GRC which comes with a 4X150
multiplier/driver
stage. I removed the front panel
from this unit also and both the 2
meter module and the 70 cm. module are
mounted on a single rack panel. I only used
the amplifier module from the
AM-1178. Both units are mil-spec cavities
for the band chosen, silver plated and require
air for cooling. The blower is a
single 150 cfm daytron blower w/squirrel
cage which feeds a fabricated plate on the
separate modules with air. A special
plate was machined for providing two
hoses to feed the individual air inlets, and
connected with 1 1/2 inch hose.
I designed the high voltage power
supply for it which provides 1500 VDC
adjustable for both units, along with full metering
(switched) for plate
voltage, grid current, screen current, and plate current. The bias and
screen power
supplies where bought from Herbach
and Rademan. I got linear power-one
supplies rated at 300 VDC (2) and
changed the resistor values for the
regulator LM723, to provide 350 VDC
continuous and 150 VDC continuous.
The 350 volt supply goes thru a
series resistor to a transistor and front
panel pot. to provide adjustable screen voltage
for setting the power level of the
amplifier. The 150 volt supply goes
thru a series resistor to a transistor and front
panel pot. to provide adjustable bias
voltage to set the operation mode
from class "C" to class "AB1", for CW or SSB use.
