Acom 03At Matching Circuit Schematic Diagram - Acom 03AT Operating Manual

5-3. ACOM 03AT Matching Circuit Schematic Diagram

The AATU ACOM 03AT comprises the following main units: RF Matching Circuit, RF Sensor, ATU Control, and ATU
Power Supply – located in the remote ATU.
Look at Fig.5-1 – the RF matching circuit schematic diagram. All relay contacts are shown de-energized (no coil
current). The matching RF circuit comprises:
A block of 8 capacitors connected in parallel to the transmitter input (CT1 - CT8), that can be activated in the
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circuit and their capacitance can be accumulated via energizing the relays KCT1 - KCT8 (the normally open
contacts are used). The capacitance for numbers one through eight increases from 27 up to 1800pF in a
geometrical progression. This makes it possible to combine random capacitance values for CT using binary
combinations between 00 and FF (0 – 255 decimally) in the range from 27 up to 4100pF with a resolution step of
27pF.
A block of 9 inductors connected in series between the transmitter input and the antenna output – inductors L1
-
through L9 - can be activated in the circuit and their inductance can be accumulated via energizing the relays
KL1 – KL9. The normally closed contacts are used in order to shunt an unused inductor when its relay is de-
energized. The inductance for numbers one through nine increases from 0,065 up to 10uH in a geometrical
progression. This makes it possible to combine random inductance values for the series L using binary
combinations between 000 and 1FF (0 до 511 decimally) in the range from 0,065 up to 23uH with a resolution
step of 0,065uH.
A block of 6 capacitors connected in parallel to the antenna side (CA1 – CA6), that can be activated in the circuit
-
and their capacitance can be accumulated via energizing the relays KCA1 – KCA6 (the normally open contacts
are used). Similarly, to the groups described above, the capacitance for numbers one through six increases from
27 up to 680pF in a geometrical progression. This makes it possible to combine random capacitance values for
CA using binary combinations between 00 and 3F (0 – 63 decimally) in the range from 27 up to 1400pF with a
resolution step of 27pF.
A single capacitor is connected in series to the antenna output (CSA) that can be activated in the circuit via
-
energizing the relay KCSA. The normally closed contacts are used in order to shunt the capacitor when its relay
is de-energized). In this way, a 250pF capacitor can be inserted in series to the antenna.
Besides the components mentioned above, there are two balanced transformers: TV2.1 and TV2.2 included between
the matching-circuit output and the antenna. The first transformer is step-up 50:200
balance for frequencies where the antenna impedance is higher than the nominal (200
Ω
200:200 and reduces the unbalance for frequencies where the antenna impedance is below 200
In parallel to each antenna insulator is connected a standard metal-sphere spark gap to guard the AATU and
correlated apparatus against atmosphere electricity during thunderstorms. A RF choke - RFC2 (80uH) is connected
in parallel to the RF input in order to bleed eventual electrostatic charges from the connected antenna to the ground.
The input signal is fed to the connector "50
connected in parallel to the input is adjusted to minimize the SWR of the input wiring for the higher band edge (it
could be omitted).
Energizing the relays KAT1 and KAT2, the RF signal can be turned to the RF sensor input J2-Sin during a tuning,
while the matching-circuit input is connected to the sensor output J3 – Sout. With both relays KAT1 & KAT2 de-
energized, the input RF power is directly fed to the matching circuit input and the sensor input is grounded. Besides,
a part of the input voltage on JP1 is taken by the capacitance divider Cu/C1 and is then detected by the diode D1.
The DC voltage on its output "+inp" is a criterion about RF power presence at the input.
During a tuning procedure, the input RF power is fed to the "RF Sensor" PCB through J2 – Sin, F1, R4, C8, C9, F2,
and then to the primary winding of the voltage transformer TV1. The RF power from TV1 secondary is split in two:
through the current-transformer TA1 primary – to the matching circuit input;
-
through the current-transformer TA2 primary – to the reference resistive load R10a,b (C10 serves for frequency-
-
compensation of the load for higher frequency band edge).
Ω
RF INPUT" - J1 on the schematic diagram. The capacitor Cc*, that is
Ω
and also provides for outputs
Ω)
. The second transformer is
Ω.
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