13.5 V
RF PA is unregulated
2.5 A
5.4
DUTY CYCLE/KEY-DOWN LIMITATIONS
The major heat generating component within the modules is the RF power amplifier which has a maximum
temperature limit that should not be exceeded. In addition, the temperature within the module itself must
be kept below the maximum temperature of the reference oscillator to ensure that regulatory frequency
stability limits are observed. As a result, depending upon the RF output power, the supply voltage, and the
ambient temperature, limits upon the average transmit duty cycle and the maximum continuous transmitter
on time exist. These limits are summarized below for operation in still air:
Ambient Temperature ( C)
Duty Cycle (%) Key-Down Time (s)
3 watts RF output
25
30
45
50
5
10
6 watts RF output
25
20
30
50
3
5
10 watts RF output
25
20
15
50
3
5
Blowing air across the unit and/or adding a heat sink to the rear of the unit where the PA module is located
can significantly improve the duty cycle/key-down times. Ritron offers an option where the case screws at
the rear of the module are longer allowing heat sinks to be attached. Contact Ritron for additional
information on this option and special instructions on attaching heat sinks without compromising the
mechanical integrity of the RF PA module.
