Procom has developed two new combiners which, the company says, ensure the highest possible decoupling between several TETRA radios.

The two- and four-station TETRA combiners provide trouble-free connections for two or four TETRA stations into an arbitrary TETRA antenna.

The four-station combiner has a highly selective helical duplex filter for each input. This filter separates the transmitter (TX) signal from the receiver (RX) signal and sends the TX channel to an isolator and the RX channel to the passive RX splitter.

From the isolator the TX signal is fed through a low-pass filter into a hybrid. And from the hybrid the signal is fed to another helical duplex filter and is thence connected to the antenna.

The RX signal runs from the antenna through the output duplex filter to a hybrid splitter, where it is divided into two (two extra splitters are required for the four-station version) and sent to the two/four input duplex filters.