I assume you are using an Etherdongle? The E1.31 spec requires that a "keep-alive packet" be sent at least every second. So yes, the scheduler and tester were transmitting at the same time. That is one reason why, in the next version, the tester will be merged into the scheduler - only a single set of data will be sent for the scheduler and tester (as long as you are using only one computer!).
Matt