Block Diagram And Principle Of Operation - Acom Owner's Manual

User's Manual | ACOM 04AT | Remote Automatic Antenna Tuner and Switch

7.3. Block Diagram and Principle of Operation

Please, see
Figure 7-1 Tuner Block Diagram
The ACOM 04AT tuner consists of the following main assemblies:
Input switch board;
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Input sensor board (located on the Capacitors board);
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Inductors board;
•
Capacitors board;
•
Output sensor and antenna switch board;
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Control board (includes modem, four service LEDs and two buttons).
•
The matching RF circuit is an L-shape matching network configuration and is comprised of the Capacitors
board and Inductors board.
The Inductors board contains 9 discrete coils that can be bypassed or added in series by relays KL1 to KL9.
Together, they form an inductor with a maximum value of over 6.25 mH, variable in 0.015 mH increments.
The discretely controlled inductor is connected in series between the tuner input (to the transmitter) and
output (to the antenna).
The Capacitor board contains 10 discrete capacitors that can be switched off or connected in parallel by relays
KC1 to KC10. Together, they form a capacitor with a maximum value of over 2800 pF, variable in 3 pF
increments.
The discretely controlled capacitor can be connected in parallel to the tuner input (from the transmitter) or
to the output (to the antenna) using two relays: KCT and KCA, respectively, forming the two basic
configurations of an L or reverse L matching network, required for the different antenna impedances:
- L-network (KCT on, KCA off) - for matching of mainly low impedances;
- Reverse L-network (KCT off, KCA on) - for matching mainly high impedances.
After the matching circuit, the RF power passes through the output sensor and the antenna switch, reaching
the selected antenna output (1 of 4). The output sensor produces four analog signals for the output forward
and reflected power, antenna current and antenna voltage: fwda, rfla, ia, and ua. The antenna switch is
controlled by four relays, KA1 to KA4. There is a lightning surge arrestor (not shown in the block diagram) at
the output sensor to protect the tuner and the devices connected to it from atmospheric discharges.
The input RF power from the amplifier, along with the +26 VDC power supply and the modem 60 kHz control
signal is fed to the input switch board, at the RF Input connector.
Here, by using suitable filters, the 60 kHz modem signal is separated and fed to and from the Control board.
The power supply +26 VDC is separated and used to derive a +5 V power supply and three auxiliary DC
voltages: +180 V, +12 V, and -12 V for the MOSFET INPUT SWITCH. The CROWBAR relay has a protection
function and is normally open. The +180 V auxiliary voltage is enabled and disabled by the HVON signal from
the Control board.
May 2021
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