[TowerTalk] Half Wave Verticals @ WWV/VH

[Jim Reid]

Hi all,

Now,  those interested,  can view an excellent photo
of the 1/2 wave verticals at WWV and WWVH.  Read
the text below the photo.  There you will discover WWV/
WWVH use elevated 1/4 wave verticals for
these HF radiators each with 9  sloping,  elevated
resonant radials!!!  If you look closely at the photo, you
will see the several elevated radials;  they come down
at a very steep angle,  and probably act more as a
real lower vertical section than what we think of as
elevated radials.  The discussion about the antennas is
a paragraph or two down below the photo.  Note the
text says the radiating radials come down at a 45 degree
angle,  but sure does not appear to be so in the photo.

Go to: http://www.boulder.nist.gov/timefreq/stations/wwv.html

You can easily see the center insulators of the towers.
What is not shown, nor discussed is the huge and extensive
ground radial field at each site.  This ground "screen" field
had to be installed to recover several dB of signal strength
out in the far Western Pacific from WWVH.  Why? Because
of the high E-field at the lower end of the down sloping radials.
The E-field at the ends of these sloping radials is very intense
because of the very high RF voltage at the radial ends driven
by the 10kW transmitters!  These fields induced very high
currents into the ground,  but the radial field eliminates much
of the ohmic loss of the induced current,  thus recovering the
former lost field strength.  Also looking closely,  you can see the
feed coax going up to the center feed point in the inside of the
right hand tower in the photo (this photo is of one of the phased
array pair out here at WWVH).  Out here,  these arrays are
right on the beach within the confines of the Navy's Barking
Sands facilities.

If you are curious, there is much other info about these stations
available on the site link above.  Note that NIST is now conducting
a survey about the use of these stations to the HF using community.
Should you want to be sure these stations continue to operate( a
pretty high cost must be spent to replace the 30 year old antennas
out here at WWVH) you may participate in this survey at:

http://www.timesurvey.nist.gov/

Hope you find this info interesting as I have.

73,  Jim  KH7M
On the Garden Island of Kauai and only about
18 miles from WWVH.


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