Thanks for the responses so far.
@stuart, what RFM module settings are you referring to? The frequency etc, as configurable through the serial interface, are the same (433MHz, network group 210, node 15, no frequency offset, quiet mode off). Part of the problem is I don’t know how to tell what code the pre-compiled hex file in that repo was produced from, so I can’t tell what’s different (if anything) about the CPP files I’m using (which are the ones at the head of master).
@pb66: yes I did also try compiling using the Arduino IDE and then copying over, this had the same behaviour. (Works in as far as interacting over serial, but doesn’t print any received data.) Normally I get about a packet per second that doesn’t match the CRC (with quiet mode off) and a packet every five seconds or so from an EmonTX that is in the house - it’s fairly close (1m) to the receiver and the pre-compiled sketch reports -20dBm signal strength for those messages.
I agree my problem might not be JeeLib, that was just one idea and I thought it would be worthwhile trying to determine what the exact version of code used to produce the pre-compiled firmware so I could try to reproduce that to begin with.