Star Type Combining Filter
The power of TX1- see fig. 1 - transmitter crosses through F1 (Double cavity band pass filter) and is rejected by F2 (Double cavity band pass filter) and sent to star point connection. The same thing happens for the power of the TX2 transmitter, that crosses through F2, and is rejected by F1 and sent to star point connection where both powers are added up and sent to only one antenna. It is important that the lines connecting the star point to the filters, have the lenghts calculated so that all the power of each transmitter reaches the antenna without reflections. It is possible to use this configuration up to connecting four transmitters working at four different frequencies, even if, in this case is not always possible. With this system the minimum space between frequencies must be at least 2 MHz, using triple cavity filters this value can reach 1.2 MHz.