I keep forgetting how to make this work, and it just came up in IRC again, so I thought I would archive the answer to the list:

per tnt:

in src/target/firmware/board/compal/rffe_dualband.c , the rffe_get_rx_ports might need to have PCS1900 instead of DCS1800

Some phones have different RF wiring and we can't autodetect it ... (the thing is that unless you try manually or look at the PCB you can't really tell ... some PCS phones have it wired to the DCS input ...)