A satellite communications interoperability module and method for frequency down-conversion. The module insertable in-line with an intra-facility link communicating a multiplexed signal between the outdoor unit (ODU) and the indoor unit (IDU). Electrical circuitry of the module transforming and forwarding the multiplexed signal over the intra-facility link, the multiplexed signal including at least direct current, a standard tone, and L-band data signals. Switching means of the module specifies operations performed by the electrical circuitry to transform the multiplexed signal frequencies, waveforms and voltages according to predetermined parameters compatible between the ODU and the IDU. An interoperability method for compatibility with a range of different indoor units applied by the interoperability module and or incorporated into an integral ODU is application of a second frequency shift upon the L-band signal output from the ODU primary down-conversion circuit.