"They purposely built a 5/8 wavelength radiator design in order to
suppress
higher lobe radiation causing selective fading at a particular radius from
the antenna. "
Actually WSM started out with something close to 5/8 wave, 878 feet.
That does have some high angle lobes, and apparently those lobes were
causing the fading problem because they were recombining with the ground
wave at about 130 miles. They then shortened the antenna to something
close to 1/2 wavelength, 808 feet, which gives all low angle radiation
with no high angle lobes.
Did you notice the efficiency number for their transmitter? 90%.
Jerry, K4SAV
Pat Barthelow wrote:
>I wonder if the sweet spot/sour spot locations are due to local land
>conditions, or are simply areas of multipath cancellation, caused by
>interaction of ground wave, and sky wave components, from a given station.
>
>Another Antenna Tower that I had the great fortune to be given a tour of,
>was WSM, in Tennessee. An unforgettable visit and tour by then (1990) Chief
>Engr Everett Lawson (SK).
>A very distinctive tower, made by Blaw-Knox, one of a handful around the
>country, from the 30's era.
>
>http://hawkins.pair.com/blaw-knox.html
>
>They purposely built a 5/8 wavelength radiator design in order to suppress
>higher lobe radiation causing selective fading at a particular radius from
>the antenna. The big bulge in the middle of the tower apparently clouded
>their efforts, and they tweaked the total height to get the best, no fade
>reception at important distances.
>
>Check out WSM on the web:
>
>http://www.fybush.com/site-020424.html (and other locations)
>
>You gotta see the tower base insulator...a Lapis Ceramic pair supporting
>tons and tons of weight.
>
>So, on the sour spots, are they specific to a single location and station?
>Or, at a given location are many, (most?) stations noticeably weaker?
>Selective Fading?
>
>Sincerely, Pat Barthelow aa6eg@hotmail.com
>http://www.jamesburgdish.org
>Jamesburg Earth Station Moon Bounce Team
>http://www.cq-vhf.com
>
>
>
>
>
>
>
>
>
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