http://www.lazygranch.com/sound/beacons/basecamp209_2.wav
AEC 209Khz.

There is a beacon at the TTR putting out XSD on 278Khz
http://www.lazygranch.com/sound/beacons/xsd278.wav
There are incorrect references to the TTR airport code being XSD. [It
is TNX] Finding a beacon at the TTR putting out XSD only adds to the
confusion.
http://www.lazygranch.com/images/ttr/xsd278.gif

Lastly, there is a beacon perhaps at Groom Lake (though it could be at
the NTS) putting put PYD on 414Khz.
http://www.lazygranch.com/sound/beacons/pyd414.wav
http://www.lazygranch.com/images/radio/pyd414.gif