I used to work for a company that provided "emergency communication services" often for hurricanes, forest fires, and other adverse conditions. The poor man's repeater was a kit built with two CDM1250/1550 mobiles and a "controller" box sold by MRE1032 on online auction sites. Each radio had its own antenna, we used 25 watt radios turned down to about 10 watts (have to watch talk-in/talk-out issues). this worked well on large conex box comms trailers, toy hauler trailers, and even on vessels. We kept everything 5 MHz apart and low power as mentioned above. We could even use RG-58 to induce some expected loss, to make it less efficient, still gaining some distance as a repeater for handheld radio users. System worked well, and many videos abound for non duplexer repeater construction.