Introduction
SRL-35 Special Features
5
SRL-35 Operator’s Manual
P/N: 1003224-01
Temperature Protection of RF Power Amplifier
RF power amplifier is protected against overheating. The power of transmitter is lowered step by step if the
inner temperature exceeds certain levels as shown below.
When the ambient temperature is under 30°C and transmitter duty cycle does not exceed 40%, the
temperature inside the modem does not exceed the trigger level.
The internal temperature is measured in the beginning of every transmission and at once when modem
cools down. The carrier power increases with falling temperature so that at 88°C carrier power goes to
10W, at 83°C to 20W, at 78°C to 25W and at 73°C the modem operates again at the full 35W carrier power.
Protection of Current
In case of a bad antenna impedance matching the current consumption of the Power Amplifier may be too
high. For this reason the maximum current is limited to 12 A. If the current tends to increase over 12 A, the
automatic power control decreases the power level until the current drops under 11.5 A. LCD indicates the
actual power level of the transmitter. A new transmission starts always with the nominal power level. The
power control scheme is applied only when the nominal power level is 35W.
Table 7. Temperature
Temperature inside a modem
Carrier power
Over 75°C
25 W
80°C
20 W
85°C
10 W
90°C
0 W (transmitter OFF)
