Abstract: Tuning a combiner filter, which includes two separate tuning modes: coarse adjustment applied when the combiner is taken into use by utilizing a measuring branch for forward power and a coarse measuring branch for reflected power; and fine adjustment applied in continuous operation by utilizing the measuring branch for forward power and a fine measuring branch for reflected power. The two-stage adjustment decreases the mutual interference of the filters during tuning. The correct tuning frequency of the combiner filter is obtained as the average point of the reversing points obtained in the adjustment process, the filter being driven to the average position. This so-called positional average tuning has two advantages: the effect of noise present in the power measuring line is reduced, and the tuning error caused by the termination of the dynamics of the A/D converter positioned after the detector at low power levels and good combiner filter settings is diminished.

Abstract: A device for tuning a combiner filter. The measuring signals (P.sub.rl . . . P.sub.rn, P.sub.F1 . . . P.sub.Fn) of a number of different combiner filters are multiplexed to the same detectors. Multiplexing allows the measuring and adjusting electronics required by the tuning and adjusting means of combiner filters to be simplified considerably especially with a high number of combiner filters. Multiplexing of measuring signals is used primarily to select the sample signals of the forward and reflected power of one and the same combiner filter to be tuned for the measuring electronics. In the invention selectors for reflected power and forward power are independent of each other, which allows isolation measurement between different channels. The sample signal of the forward power of one combiner filter and the sample signal of the reflected power of another combiner filter are thus connected to the measuring electronics.