As far as I can tell there is no way to display UTC time on the main operating screen on the 6600M. That would be very nice. I have the GPSDO installed, and it keeps great time. I can, of course, go into >Menu>Radio and see the displayed time, but I would like to have it displayed on the operating screen. There's plenty of space. I'd suggest just to the right of where the power level appears. Perhaps, some would not want this, so I'm just suggesting an option. Could this be done in a future firmware release?