I had the same issue with my 7100 via USB. I called Icom and got a guy who knew the whole story. The USB cable sends out serial in packet format, so it sends it in bursts of data. A short "chat" line can take 3-4 keys of transmit. The data cable (I use orange RT Systems) sends a continuous serial data stream. Makes sense and those have been my results. I do not have this issue with bluetooth, FWIW. On either my 5100 or my 4100. Works exactly like the data cable.?
