Protections; Swr Protection; Overcurrent Protection; Thermal Protection And Fan Control - Kenwood TS-890S In-Depth Manual

Protections

The TS-890S employs a final amplifier circuit configuration for a 100 W transmit power output with sufficient margins.
Consequently, protections against large currents and excessive heating are provided, taking account of safety

SWR Protection

Not only does a high antenna SWR impede efficient radio wave radiation, distortion may occur in the final circuit due
to the reflected waves, and the TS-890S or the antennas may be damaged as a result. To prevent such a problem from
occurring, a protection circuit is implemented to reduce the transmit power to reflected waves. The protection circuit
starts reducing the transmit power when the SWR becomes 1.5 or higher.

Overcurrent Protection

A protection circuit is implemented to monitor currents in the final amplifier and prevent currents over a specified level
from passing through.

Thermal Protection and Fan Control

The TS-890S is equipped with two final amplifiers with thermistors placed near them. The thermistor monitors the
final FET temperature and switches the rotating speed to one of the three levels based on the detected temperature.
The "Cooling Fan Rotation Speeds and Final Amplifier Fan Activation Temperatures" table shows the relationship
between the speed of the cooling fan for the different components and the final amplifier temperature. If the final
amplifier temperature continues to rise even while the cooling fan is running, the transmission power will be limited or
transmission will be stopped and restored to the receiving state to prevent malfunction.
Table 5 Cooling Fan Rotation Speeds and Final Amplifier Fan Activation Temperatures
Fan Rotation Speed
Low
Medium
High
TRANSMISSION CIRCUIT 03
Final Amplifier
Approx. 60 °C
Approx. 70 °C
Approx. 75 °C
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