Some years ago I was listening to the NASA audio feed of a high inclination orbit space shuttle launch.
Shortly after the external tank tank was jettisoned the crew remarked "looks like we're going to have to secure uniform, we've been advised by an RAF bomber crew that we're transmitting on an unauthorized frequency".
The shuttle in that era had a wafer switch that selected 296.8, 259.7 or 243.0 on the UHF control panel.
See:
http://spaceflight.nasa.gov/shuttle/...bcomm/uhf.html
There is no small irony in Americans trying to enforce R/T discipline. Before 911 domestic flights rarely monitored guard and international types used it mostly for ride reports and sports scores over the water. After 911, it is monitored religiously even on domestic flights lest you be intercepted and have to fill out paperwork.