I use a DPSI Twin on my big-scale Extra. Too big for my jet. Here I use a DPSI Mini with only one receiver.

MC-24 transmitters can be fitted with two HF modules in different frequencies (35 and 40MHz...). But you can't do this "at home". It transmit 2 freq on same antenna.

I use two MX-22 to transmit to those two receivers. I linked them with a cable. I only do that when are too many pilots on the field.