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The Wattmeter unit is based on a bridge circuit which comprises the current transformer T401 and some other
components (not shown in the block diagram). It measures the forward and the reflected power at the amplifier
output and feeds information to the Control unit for indication and development of the protection functions of the
amplifier.
The DC bias voltages for the gates of the final transistors are produced by the “Bias control and Measurement”
circuit. In the Technical compact disk (CD – option to the amplifier) is given a procedure for adjusting the idling
current of the transistors.
b) The Control unit of the amplifier is based on a digital signal processor (DSP) manufactured by
MICROCHIP. The Control unit implements the following functions:
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controls the operating modes: Stand-by, Operate/RX, Operate/TX etc.;
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measures and monitors the analogue and digital signals in the amplifier;
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protects the amplifier from overloading and the critical regimes at wrong operation or abnormal ambient
conditions;
- files in the amplifier nonvolatile memory a log of the last 28 switching offs type “serious failure” (HARD
FAULT) and the amplifier parameters registered at the moment of faults rise. They can be visualized or
downloaded in a plain-text format file by the operator’s wish;
- by means of the system interfaces the Control unit monitors the staus and controls the operation of all
modules in the amplifier: display and keyboard, frequency counter, wattmeter, power supply unit,
FSK/ATU (for control of external Automatic Antenna Tuner or Antenna Selector from ACOM – ready for a
future development), Power Amplifier Module (PAM), and low-pass filters unit (LPF).
The user interfaces of the Control unit allow connection with additional external devices:
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CAT/AUX interface for connection with various transceivers;
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RS232 interface for connection with computer or Remote Control Unit.
In order to facilitate the diagnostics of possible failure, after which the amplifier modules should not be powered
before the failure has been repaired, a special regime is designed. By means of a low power DC external source
only the Control unit can be powered, so that the data from its nonvolatile memory can be downloaded and saved
in a computer plain-text format file for further analysis and troubleshooting (the FAULTS LOG with the history of
the last 28 protection trips of the type HARD FAULT). See also Sections 4-6(c), 5-5, and 7-4.
c) Power Supply Unit
The main power switch (POWER ON) is located on the rear panel of the amplifier. It interrupts the mains cable
right after the main fuses and cuts off supply to all internal circuits. When switched ON it starts only an extra- low-
power AC-DC converter providing the Low Energy (waiting) mode of the power supply with a negligible
consumption (below 1VA). There are three different ways to activate the amplifier from waiting in the working
mode:
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locally (manually) – by pressing the “ON-OFF” button on the front panel (Fig. 3-1) for 1-2s;
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remotely - by applying a low-power DC pulse to the remote turn-on and turn-off line “ON_RMT”: +4.5 to
+15V DC towards ground for 1-2s – see S. 2-4(a); this line is brought to connector CAT/AUX pin 11 and
its consumption does not exceed 3mA;
- remotely – by the serial RS232 interface – through the simultaneous activation of the RTS and DTR
hand-shake signals for 1-2s (normally they do not overlap while they serve for control of the serial data
flows exchange).
Irrespective of how the amplifier has been activated, it can be de-activated - returned to the Low Energy (waiting)
mode of the power supply - in any of the above three ways or using the “OFF” serial command by the RS232
interface. At tripping a protection of the HARD FAULT type, the amplifier is self-protected, returning to the same
Low Energy (waiting) mode of the power supply and only the extra-low-power AC-DC converter remains running
with a consumption below 1VA.