Down Converters are parts of a microwave link. Microwave signals like DVB-T with COFDM modulation are for example generated from a wireless video transmitter in different frequency bands. Common video receiver input frequency range goes up to about 1 GHz. All frequency bands above 1 GHz like L-Band, S-Band or C-Band can be converted in the receiver input frequency with a frequency converter. These frequency converters are named down converter, LNC (low noise converter) or LNB (low noise block). The down converter normally is a combination of low noise amplifier, RF filter, RF mixer and a local oscillator to generate the mixing frequency. Water resistant down converters can be installed directly at the antenna. The down converted signal (IF signal) of the converter can transferred with a coaxial cable to the receiver. In most applications the supply voltage for the down converter comes from the receiver (remote power supply).Microwave links can be found in very different applications. A main part is the transmission of video and audio signals from events, sport events or surveillance applications.
Helicopters or air crafts are used as relay stations in microwave links. In this applications there are down converters, receiver, modulator and power amplifiers installed in the helicopter of air plane to receive the signal and transmit it to a radio van.