One or more upstream line cards each include a digital or analog multiplexer front end circuit for a Cable Modem Termination System. Each upstream line card has only upstream receivers and allows a CMTS to share one or more receiver chips to receive and recover data from a larger number of input cables coupled to the front end multiplexer. A control circuit for the multiplexer uses MAP data and burst assignment data and upstream mini-slot counts for each of the input cables to determine when a burst is about to arrive on a cable and cause appropriate switching by the multiplexer or crossbar switch. In some embodiments, there is only one RF channel circuit coupled to the output of the multiplexer, so the multiplexer is controlled to couple the input cable upon which the burst is expected to the single RF channel. In some embodiments, the sample data generated by each RF channel is buffered and an arbiter picks one burst at a time for application to the input of a CMTS receiver or doles out bursts to different receivers. In other embodiments, no buffers or arbiter are used, and each RF channel has its own dedicated CMTS receiver.