Acom AOM 04AT User Manual page 71

User's Manual | ACOM 04AT | Remote Automatic Antenna Tuner and Switch
The process of full tuning runs in a number of steps (see Section ) and at each
5.1 What a Full Tuning Cycle Does
step the Control board enables and blocks the RF power through the MOSFET INPUT SWITCH mentioned
above. During that time, the transceiver feeds continuous RF power. At each step the controller first activates
the sensors with a short pulse of RF power by blocking the MOSFET for a short time, and in a few milliseconds
reads out the status of the sensors, then it blocks the power to the relays by saturating MOSFET again, and
in this manner switches the relays synchronously with the power and keeps the contacts safely clean (see
Section ).
5.1 What a Full Tuning Cycle Does
After each relay switchover cycle, the control board applies RF power to update sensor measurements and
read their new state. This is done by the *RFON signal and only lasts a few milliseconds (until the sensor
readings are stabilized); then the control analyzes again the information read by the input sensor - "R", "G",
"PH", "fwd" and "rfl", in order to evaluate the current position of the transformed impedance against the
goal (50+j0) Ohm. While the RF power is enabled the relays will not switch.
After analyzing and evaluating the result of the subsequent relay switching, the Controller board makes a
decision which capacitors and inductors to be included and which ones to be excluded from matching circuit
at the next step. The decision is made following a specific tuning algorithm in the program memory of the
Controller board.
The algorithm is built in such a way that the process is always convergent, i.e., the transformed impedance
converges to the circle with SWR < 1.3:1 toward 50 Ohm, regardless of the wide variety of expected antenna
impedances in the frequency range, using the available resource of coils and capacitors to the maximum
possible extent, according to the operating frequency.
At each subsequent step, the Controller board enables RF power briefly, analyzes again the result from the
data of the input sensor, makes a decision for the subsequent commutation, etc.
The tuning proceeds with multiple successive attempts, following the controller algorithm. Before switching
each relay, the power is stopped and the new relay state is set.
After waiting a certain amount of time for the relay contacts to settle, a new RF pulse follows, with sensor
reading power included, etc., until the impedance transformed by the L-network enters the range of
impedances with SWR < 1.3:1, or until the coil and capacitor resource is depleted (e.g., if the SWR of the
antenna is too high, so no tuning can be found).
At the end of the tuning process, the tuner Controller board reports the result of the tuning to the amplifier,
and waits until the operator stops transmitting. Then the tuner Controller board disables the relays KS1 and
KS2 (RF power delivery to the tuner is stopped). This switches the RF output of the amplifier directly to the
input of the already tuned antenna circuit, and the tuner is ready for operation. The combination of relays
found to achieve good tuning is stored in the tuner nonvolatile memory automatically.
October 2023 S e c t i o n MAINTENANCE | Page 71 of 88