Jim Dalke
SEATTLE - On
January 1, 2002, KKOL, 1300 kHz, began operating from temporary facilities
installed aboard the 175 foot cargo ship, the "Coastal Ranger," in
Seattle’s Elliott Bay. This 1000
watt transmitter facility is the only licensed broadcast station operating in
the United States aboard a ship. The combination of a Valcom fiberglass whip antenna installed
on the deck of this steel hulled ship and moored in seawater is providing
outstanding coverage for the Seattle area.
THE AUTHOR
James
A. “Jim” Dalke is an innovator in media and telecommunications technologies.
Jim is the holder of numerous telecommunication and media patents and has
presented papers on advanced broadcast technology projects for the National
Association of Broadcasters and the National Cable Telecommunications
Association. Jim is a Certified Professional Broadcast Engineer and a
member of the Society of Broadcast Engineers, the Society of Cable
Telecommunications Engineers, and the Society of Motion Picture and Television
Engineers. Jim holds Extra Class
Amateur Radio license W7CAN
HISTORY
KKOL AM, 1300 kHz, first went on the air in the 1920’s as KOL, one of Seattle’s first radio stations. For many years, the station’s studio and transmitter were located on Harbor Island, just south of downtown Seattle amid busy shipyards and stevedore operations.
In the mid 1970’s, the station abandoned the Harbor Island studios and the historic KOL call sign. The station continued to transmit from the aging 400-foot self-supporting tower on Harbor Island.
In the 1990’s, the Port of Seattle began aggressively upgrading and expanding their ship container operations on Harbor Island and needed the land occupied by the transmitter and tower facilities. In the summer of 2001, the Port came to an agreement with Salem Communications, KKOL’s owners to abandon the Harbor Island transmitter facilities by January 1, 2002.
An application was filed with the FCC for a new 50,000 Watt replacement facility about 15 miles south of the Harbor Island site.
THE CHALLENGE
To prevent the station from going dark while the new facility is being constructed, it was decided to search for a site for a temporary transmitter facility under the FCC rules for Special Temporary Authorization (STA). The objective was to preserve as much of the original licensed coverage area as possible. Since the operating power would be less than the licensed 5 kW, and a temporary site likely to be inefficient, a location as near the original Harbor Island site and downtown Seattle as possible was desirable.
Many towers and smoke stacks were evaluated for use as a temporary
antenna, but for various reasons, none appeared to be suitable.
Alternatively the temporary facility could be multiplexed with another
station. An antenna that has the
potential to be shared is located about a mile south of Harbor Island on a hill
in West Seattle known as Pigeon Point. The
tower is shared by KBLE 1050 and KKDZ 1250.
However, 1250 is too close in frequency to allow third transmitter on
1300. FCC and zoning issues preclude erecting a conventional tower,
even for temporary use.
Several years ago, Valcom Ltd., a Canadian manufacturer of fiberglass whip antennas developed a center-loaded version for AM broadcast applications. The Valcom antennas have proven use for marine applications, and it was determined that this type of antenna could be mounted on a steel hulled vessel and moored in seawater for efficient AM broadcast.
The Valcom antennas have been used with a traditional radial ground systems in several locations where the conventional taller antennas could not be used.
Harbor Island is a flat landfill between the industrial area south of
downtown Seattle and a peninsula across Elliot Bay known as West Seattle.
In the past the east shoreline of West Seattle was crowded with
commercial shipping docks and warehouses, fish processors, and marinas.
Over the years, much of this shoreline has been cleared and converted into a
shoreline park with a magnificent view of the downtown Seattle skyline.
The only significant commercial building left is Salty's, one of
Seattle's finest waterfront restaurants. To the south of the restaurant is
a cleared strip of land with one small building occupied by a fish processing
company.
A 300-foot deck pier parallels the shoreline of this narrow strip of
land. A plan was developed to mount
the Valcom fiberglass antenna on the deck of a steel-hulled ship or barge, and
moor it to the pier. The
steel-hulled vessel, moored in the conductive seawater of the bay, would provide
an effective ground system, substituting for the traditional copper wire radial
system.
THE SOLUTION
A search of the Seattle’s many waterfront docks and waterways was made for a suitable ship. The search included the Internet, and it became apparent that many old cargo ships and fishing boats were available.
The 175-foot cargo ship, the "Coastal Ranger," was identified as a possible vessel. The ship is one of a fleet owned by a Seattle company, Coastal Navigation. The fleet is used to deliver supplies to Alaskan fishing companies, and return to Seattle with the cargo holds filled with fish. The Coastal Ranger was one of the oldest of the fleet and with the Alaskan fishing industry not very profitable, it was not likely to be needed for shipping in the near future.
PUTTING IT TOGETHER
A lease for the boat and the necessary moorage for the boat near Harbor Island was obtained. The ship was moored at the Coastal facilities in the freshwater Lake Washington Ship Canal in the Ballard area of Seattle.
A 74 foot Valcom antenna was tuned for 1300 kHz operation and shipped to the Ballard location. A Broadcast Electronics 2.5 kW transmitter was also shipped to the Ballard site.
A Valcom steel hinge plate was welded onto the aft deck over an area that had substantial reinforcement directly below the deck plate. The plate was mounted on a 45-degree angle so the antenna could be assembled on the dock. The antenna was raised using a boom crane mounted on a truck. The boom truck normally was used to load freight onto the ships that were regularly in and out of the facility.
A
standard 20 foot cargo shipping container was lifted onto the aft deck and
secured to the deck using the deck retainer locks already in place for that
purpose. The double doors at the
end of the container were replaced with a wood wall with a door and a
ventilating fan installed. The BE
transmitter was installed in the container along with a rack with monitoring and
remote control equipment. The ATU
was installed on the container wall with a feed through for the antenna feed.
With the antenna and transmitter installed and secured, the ship was moved from the Ballard moorage through the Lake Washington Ship Canal locks to the new moorage on Elliot Bay.
The necessary 220 volt shore power and telephone lines were installed providing power and communications to the boat.
A simple ATU was constructed and pretuned to the Valcom specifications by Carl T. Jones Engineering. When the transmitter was powered up, very minor tuning was required for minimum SWR.
POWERING UP
The new "maritime" facility aboard the boat was turned on January 1, 2002 and has been operating reliably 24x7 since.
One concern was the effect of the tide levels. Elliott Bay gets more than 16 foot tide swings from time to time. Very little or no variation in base current or field strength has been detected even at the extremes.
Another concern was the effect of wind and waves as the boat pitched and rolled. The boat is in a protected moorage, so wind and wave action is minimal. There is virtually no pitch because of the boats 175-foot length, but some minor roll, probably less than a degree or two has been observed. You can see some minor sway at the top of the whip, but no variation in signal has been observed.
PERFORMANCE
The facility performance is outstanding. The signal from the STA site has been consistent and reliable, and covers a significant percentage of the original licensed coverage area. Several sets of field measurements were made to determine coverage and efficiency.
Included in this report is the 5-mv contour map based on some 40 field measurements. The contour covers a major portion of the area encompassed by the Seattle City limits.
Several
field measurements were made to compare the STA operation with the field from
KBLE 1050 kHz, and KKDZ 1250 kHz, both operating at 5 kW from a site known as
Pigeon Point about a mile south of the STA.
The measurements indicate the STA is operating at about the same
efficiency as the traditional tower and radial ground system on Pigeon Point.
The third set of measurements were made along the shoreline of Elliot Bay, across the bay from the STA site, in a NE quadrant to determine the 1 km field over saltwater. The measurements were plotted on the FCC’s Groundwave Field Strength Graphs for 1300 kHz. The results of this plot indicate the effective field at 1 km over the saltwater to be about 300 mv., considerably higher that the FCC requirements for traditional antenna systems.
Westward view of the boat. Note Valcom antenna and gray cargo container on the stern.
View of downtown Seattle looking east across Elliot Bay from the STA site.
View of mounted Valcom antenna and cargo container housing the transmitter
Closeup view of the Valcom antenna mounted on stern deck
Approximate
5 mv contour, KKOL STA
Based on actual field measurements
PERFORMANCE MEASUREMENTS
The antenna base impedance was measured with a standard impedance bridge connected between the ATU and the Antenna feed. The antenna base input was measured at 12.1 –25j ohms. The antenna base current was set at 9.05 amps to correspond with the FCC STA power level of 1.0 kW. With some minor tuning, the input impedance of the ATU network was set at 51.5 +0j ohms. The transmitter SWR meter indicated an excellent match.
Base Impedance measurements at 10 kHz Intervals
Five sets of field measurements were made to compare the STA operation with the field from KBLE 1050 kHz, and KKDZ 1250 kHz, both operating at 5 kW from a site known as Pigeon Point about a mile south of the STA. The values in the Diff dB column represent the relative difference in signal strength between the two stations, and the Norm dB value is a normalized value compensating for the power difference between the two (1 kW vs 5 kW) The measurements indicate the STA site is propagating at about the same efficiency as the traditional tower and ground system on Pigeon Point.
Ground Wave Field plotted from field measurements along
the periphery of Elliot Bay.
Seattle - A pier fire nearly engulfed the Coastal Ranger April 29, 2003. The Seattle Fire Department was able to pull the ship to safety.
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Copyright ©2002,2003,2004 James A. Dalke
No part of this site may be reproduced in any form without permission.
This site last updated September 28, 2002
For more information contact jim@dalke.com