Strange Antennas

I recently (9/1/07) visitedMt. Constitution on Orcas Island (Northwest of Seattle, WA) and Mt. Erie (Just south of Anacortes, WA).

The views from both peaks were outstanding with water, land and other mountains in view.  The peaks were well populated with radio systems as many mountain tops are, but there were some strange antennas to be seen on each peak.  

On Mt. Constitution the main tower is shown below.  Nothing unusual about it - two broadcast stations and a bunch of other radio systems.

Top of antenna tower

However, inside the fence at the base of the tower was a shielded loop antenna.  It's typical of shielded loops used at HF, MF and below, obviously not for VHF or UHF so it wouldn't benefit from being on top of a 2400 ft. mountain.  It's certainly not whatI would expect to find at a Mt. top radio site.  Strange!  

Shielded loop antenna

FCC radio site 1033080 was on Mt. Erie, and the top of its tower is shown below.   The antennas that are new to me are the two flat semi-circular ones with the concentric circles or spiral atop them.  I had not seen anything like them in the past.  Again strange, at least to me.

Top of radio tower