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 How do I turn the SWR Meter on? SR-447HPC2 Setup Guide Tuning Your Antenna for the Lowest SWR 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.. Comments 0 comments Article is closed for comments.