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File:KGO-AM transmission towers SF Bay.jpg

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The three-tower transmitter of KGO/810am, which has been the Bay Area's most popular radio station for more than half a century. KGO's three towers alongside the causeway at the east end of the Dumbarton Bridge, are perfectly sited for AM radio, which travels best over the most conductive ground. There is no more conductive ground than salt water, and salt ponds like this one are the saltiest water and land on Earth. KGO transmits with 50,000 watts from towers 1/4 wavelength high, or about 250 feet. The three towers radiate <a href="http://www.fccinfo.com/CMDProEngine.php?sCurrentService=AM&tabSearchType=Appl&sAppIDNumber=249372&sHours=U" rel="noreferrer nofollow">a directional pattern with two large lobes</a>, one to NNW, toward San Francisco and the other to the SSE toward San Jose. At night the signal reaches the whole West Coast by bouncing off the ionosphere. Its nulls between the lobes have the effect of minimizing signal toward the WSW, where there are unpopulated areas beyond the adjacent Bay Area (which still gets a good-enough signal), and toward the ENE, toward Schenectady, New York, where KGO protects WGY there — or did when the rules were created, back in the 1930s, and "clear channel" stations were protected at night. KGO by day covers a <a href="http://radio-locator.com/cgi-bin/pat?call=KGO&service=AM&status=L&hours=D" rel="noreferrer nofollow">large part of California</a> with fringe reception stretching from Eureka in the North nearly to the South Coast.

Oh, and two of the three towers that stood here until 1987 were destroyed in the 1987 Loma Prieta earthquake. KGO used the remaining tower as a non-directional radiator until all three were rebuilt a year or two later.
Date
Source 2008_11_09_bos-sfo_094
Author Doc Searls from Santa Barbara, USA

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This image was originally posted to Flickr by dsearls at https://flickr.com/photos/52614599@N00/3022109312 (archive). It was reviewed on 26 January 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-sa-2.0.

26 January 2019

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9 November 2008

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Date/TimeThumbnailDimensionsUserComment
current06:47, 26 January 2019Thumbnail for version as of 06:47, 26 January 20192,617 × 1,962 (3.88 MB)TillmanCropped 20 % horizontally, 20 % vertically using CropTool with lossless mode.
06:45, 26 January 2019Thumbnail for version as of 06:45, 26 January 20193,264 × 2,448 (6.03 MB)TillmanTransferred from Flickr via #flickr2commons

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