I thought I'd try an experiment. My wife thinks I'm gardening, but if that's not a good time to play with my GPS, when is?
Monitoring my Aera 500 in between feeding my new Bosch garden shredder (a device that can only possibly have been designed by an off-duty aeronautical engineer), I'm getting a consistent predicted accuracy of 10ft, and a periodic signals on satellite 37 and 39.
That seems to imply that BEagle is correct.
G