I think I am okay for the short haul, which is the main requirement, but I had one of those what if moments, where I thought it would be nice for the guy in the tunnel where his instrument would send data to a data display unit just outside the tunnel for the attendant to view. 10 dBm is like the max level of a sig gen so I don't imagine that working out well, but I do have a way to go up to +27 dBm. To conserve battery power on the remote unit I would want some sort of power control where we start at a high power then drop the power as low as possible to maintain a link. Kinda like they do in cellphones.