FAQs from Rohde & Schwarz

Antifreeze Mode in THx9


Description of Antifreeze Mode in liquid cooled transmitters THx9


Transmitter THx9 are equipped with a „so-called“ Antifreeze mode. This mode allowes the fans in a heat exchanger remain in operation with low speed to avoid freezing under very cold weather conditions (snow & ice). The Antifreeze mode is only active when the transmitter has been switched OFF. In this state (e.g. a standby transmitter in a N+1-system) the pumps are not running and no heat is created in the power amplifiers. There is no flow through the heat exchangers, the heat exchanger has nearly outside temperature. To avoid freezing therefore the fans are constantly operated with a very low speed of 8%.

As soon as the transmitter is switched ON, the Antifreeze mode is deactivated. The amplifiers are creating heat and due to the running pumps there is a constant flow of warm coolant through the heat exchangers. Therefore a freezing of the fans is very unlikely. When the set point temperature in the cooling control can not be reached, the fans are reduced in their speed down to 0% until the coolant temperature is reaching the set point value again. Then the fans are starting.

Depending on the usual environmental conditions it is important to set a reasonable setpoint temperature: If it is set too low, the fans are permanently running with full speed, this creates noise and higher energy consumption. If it is set too high the fans are permanently fluctuating between zero and high speed.

To avoid condensation inside the transmitter due to cold coolant, the fans are automatically disconnected from mains supply by a thermal switch when the coolant temperature drops below 15°C.

  • Path to activate the Antifreeze Mode: Task View (Home) > Setup Cooling > Fan Control
Antifreeze Mode in THx9