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? Tuning Your Antenna for the Lowest SWR SR-447HPC2 Setup Guide When I transmit the CH Display shows 00 and 2.1. What is my radio showing? Comments 0 comments Article is closed for comments.