A transmitter includes an up-converter and a modular receptacle. The up-converter is coupled to convert an input signal into a Radio Frequency (RF) signal having an output frequency, and is configurable to adjust the output frequency over a frequency range containing multiple sub-bands. The modular receptacle includes a first interconnection adapter coupled to the up-converter and a second interconnection adapter for coupling to an antenna. The receptacle is configured to receive between the first and second interconnection adapters a Power Amplifier (PA), which is selected from a group of power amplifiers each covering a respective sub-band in the frequency range.