I've just tried that and it gives a much better result. Pin 11 with a straight key/constant send was 4.98V and the voltage at the dummy load was a constant 13.8V. I've also checked pins 12 and 13 and they are behaving correctly. 5V on receive, dropping to 0 on transmit.
Sadly, having connected it to an antenna I still can't detect any signal using my SDR.
