Thanks Chas. I have a Radar Maint.Cert. but never come across that set-up, I guess a waveguide would need some sort of rotating joint....but, these days I should think the signals are "video-only" exiting the transceiver within the external casing. Modern electronics eh? How things change.....

The radar and mast are seperate items. The radar just pivots around hinge on rear of wheelhouse. see http://www.shipspotting.com/gallery/photo.php?lid=2178617

Of course! Seems obvious now, especially with the guard rails all around.
Many thanks!

A radar antenna on a fold-down mast.

What is that round white object, starboard-aft of the wheelhouse? Looks like some kind of transponder?

Superb photo, Netty. Just look at that water (as well as the tug, of course)