Codan Radio Communications AMP-4-470 User Manual

Output power control.

In the local control mode, the 3-turns potentiometer “PWR CTRL” is used to set the output power. The
range of regulation lays between more than 30 W (when the potentiometer is rotated completely
clockwise) and less than 20 W in the opposite direction (both numbers are valid for the nominal power
supply voltage, greater than 13 V, and RF drive, greater than 6 W). The potentiometer will start clicking
when the end of the range is met.

In the remote control mode, the output power depends on the voltage at pin Z22 of the DC connector
(Vctrl). This voltage may change from 0 to 9.5 V. When Vctrl < 1 V, the PA works as an attenuator,
and not more than 0.2 W is available at 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…7V.

The output power is also controlled by the load mismatching, overvoltage and overheating protection
circuits. In the case of the load mismatching the power is reduced proportionally to the VSWR value,
starting from VSWR > 2. In the case of overheating (when the temperature of the heatsink exceeds
+85°C), the unit 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 unit status monitoring: LED at the Front Panel and signals at pins of the DC
connector.

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

A LOW level of voltage (less than 2 V) at the monitoring pins of DC connector gives details about the
alarm:

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

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.