[Elecraft] DF antennas

[Stuart Rohre]

Michael,
Several years ago, FCC replaced manned field sites with remote controlled
Wollenweber arrays, antennas formed in circles at sites that can DF any
compass direction.  They are controlled out of MD FCC site.  Yes they can DF
well on sky waves.  They can remotely determine which sites have the best
versions of the signal they wish to track, and can use multiple sites to
triangulate the source.

If ever you see an old photo of the island on the carrier Enterprise circa
1968, it had a Wollenweber type set of dipoles all arrayed around the top of
the island, just below the bridge.  They have since changed those out for
other means.

Data that is sent in bursts is more difficult to track, if the period of the
signal is random.
Besides spread spectrum, there are many modulation types that can be used
effectively, besides coding the messages by crypto means.  We should be
vigilant and know what signals "should" be in our ham bands in case
intruders show up there.

The K2 with its great dynamic range and strong signal handling makes an
excellent receiver for catching stealthy low power transmissions in its
bands.

-Stuart
K5KVH