GU-81M tube power amplifier

The shortwave power amplifier is made according to the classical scheme by a common cathode on a GUU-81M tube.
This is an "old", reliable, time-tested lamp with graphite anodes and does not require forced cooling.
With anode supply voltage + 3kV, stabilized supply voltage of the second grid + 750V and a resting current of 100mA,
the amplifier develops an output power of 1kW on the 50Ohm load in the frequency range 1.8 ... 29.7 MHz.
At the input of the amplifier power is supplied 25 ... 30W.

The operational characteristics of this amplifier are fast (2 ... 3 s) readiness for operation,
"soft" switching and silent operation, protection against short-circuit and overloads.
After power-up and warm-up of the VL1 lamp, for 2 ... 3 s the amplifier is ready for operation,
with a significant advantage of the use of GG-71, GU-13, GU-81M lamps, with excellent linearity and no interference.
The level of the second harmonic at the output of the UM, at Pout = 1 kW, was -40 ... -55 dB at 28 ... 1.8 MHz.

The front panel of the amplifier contains controls, indication and control.
On the rear panel there are input and output connectors, control socket, ground terminal,
fans and circuit breakers. All RF connectors, ground terminal, CPE and blocking capacitors
The RF unit is connected to each other by a copper strip (bus) running along the centerline of the
housing between the front and rear panels.