A combining arrangement comprises a power combiner having at least four ports. A first match-dependent oscillator is connected to input power at a first frequency to a first input port of the power combiner. A second match-dependent oscillator is connected to input power at a second frequency to a second input port of the power combiner. A mismatch is connected to a third port of the power combiner. The power combiner is operative to combine power from the first and second oscillators and, when the first and second frequencies are different, to apply a fraction of the combined power to the mismatch. The mismatch reflects at least some of the fraction of the combined power to the first and second oscillators to phase and frequency lock their outputs. A fourth output port of the power combiner is connected to receive the combined power. The power combiner attenuation is variable to adjust the proportion of the combined power split between the third port and fourth output port from 0% to 100% of the total combined power for any power values at the first input port and second input port.