When I try to transmit, my 447HPC2 displays E4 and won't key. Shawn November 11, 2016 22:43 You have a high SWR. E4 means SWR protection mode stopped the radio from transmitting to avoid damaging your radio. Related articles SR-447HPC2 Error Codes and what they mean SR-447HPC2 Setup Guide How do I turn the SWR Meter on? When i key up on channel 19 it changes to 00 and 2.1 trying to figure out what this means and if it's good or bad.. Tuning Your Antenna for the Lowest SWR Comments 0 comments Article is closed for comments.