Codan Radio Communications AMP-4-150 User Manual

Output power control.

In the local control mode, the 3-turn potentiometer “PWR CTRL” is used for the output power setup.
The range of regulation lays between more than 30 W (when the potentiometer is rotated completely
clockwise) and less than 20 W in opposite potentiometer position (both numbers are valid for the
nominal power supply voltage, greater than 13 V, and RF drive, greater than 6 W). The potentiometer
limit is indicated by a clicking noise.

In the remote control mode the output power depends on the voltage applied to pin Z22 of DC connector
(Vctrl). This voltage may change from 0 to 9.5 V. When Vctrl < 1 V, the PA works as an attenuator, and
no more than 0.2 W goes from its output. The minimum rated power (20 W) is reachable with Vctrl ~ 4
V; the maximum rated power (more than 30 W) is reachable, when Vctrl = 6…7 W.

The output power is also controlled by the load mismatch, overvoltage and overheating protection
circuits. In the case of the load mismatch, the power is reduced proportionally the VSWR value, starting
from VSWR > 2. In the case of overheating (when the temperature of heat sink exceeds +85°C), the PA
switches to stand-by mode. When the power supply voltage exceeds 17 V, the output power falls to less
than 0.2 W.

Unit Status Monitoring.

There are two features of PA status monitoring: front panel LEDs and signals at pins of DC connector.

LED “TX” is on, when the output power is not less than 20W.
LED “G/F” is on, when the power supply voltage exceeds 17 V (in active mode only), or if the
temperature of heat sink exceeds +85°C (in both active and stand-by modes).
LED “VSWR” is on, if the load VSWR is greater than 2:1.

LOW level of voltage (less than 2 V) at the monitoring pin of DC connector witnesses about the alarm:

at pin B24: The power supply voltage exceeds 17 V (appears in active mode only), or heat sink

temperature is greater than +85°C;

at pin B26: The output power is less than 20 W(appears in active mode only);

at pin Z26: The load VSWR is greater than 2:1.