[Antennas] vertical dipoles

[Jim Reid]

Aloha from the Garden Island of Kauai,

A few of you have reported difficulty in getting to the
antenna photos out here at WWVH.  Try this link,  then
click on the particular photo of interest for the large view:

http://www.boulder.nist.gov/timefreq/stations/wwvh.htm

Click on the button "WWVH Photos".
The second row of photos down holds the antenna shots.

The reason for the radial cables on the ground is to provide
conductors to terminate the "E" fields from the lower ends of
the down sloping cables which form both guying and the lower
end of the vertical dipole (in sleeve antenna fashion; the sleeve
configuration allows the coax to go up to the center feed point
without the coax being exposed to the radiated RF fields; you
can just see the coax in the nearer 15 meter vertical if you
click to enlarge that photo).  With out those radial conductors,
the E fields (voltage gradients) would induce currents into the
soil;  this cost the installation a big drop in field strength out
in the far Western Pacific.  Installing the radial field restored
the signal strength out there.  Remember,  the ends of a dipole
are high voltage (high E field) places,  and,  of course,  no
current flow,  hi.

73,  Jim  KH7M