LBA Technology Supplies a Low-Profile Antenna for US Coast Guard NAVTEX System on Guam

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A new cost-effective antenna system for transmitting navigational messages to ships upgrades broadcast coverage by combining a compact and innovative dual frequency design and remote control - all while reducing the profile of the tower itself.

Ships sailing in waters near Guam have a new connection to shore. The US Coast Guard's NAVTEX coastal telex broadcast system has been upgraded by replacing three conventional 300-foot vertical towers with one small-aperture SAMWAS antenna.

The unique SAMWAS medium wave antenna system is a product of LBA Technology, a North Carolina telecommunications firm with more than 40 years experience in antenna innovations. The company's engineered solution for the Guam site can be replicated at most other NAVTEX locations worldwide.

The coastal telex broadcast system called NAVTEX is a vital link for commercial and military ships operating within 400 miles of a coastline. NAVTEX is a maritime safety system typically operated by navy, coast guard, or lighthouse authorities in coordination with the International Maritime Organization (IMO). Narrow band teletype messages carrying weather reports, search-and-rescue bulletins and other navigational information are beamed to text printers on ships from transmitters at coastal locations around the world. The shore-to-ship signals are sent out at either 518 kHz or 490 kHz.

For the US Coast Guard transmission facility on Guam, LBA Technology used a suite of subsystems called SAMWAS-200 that features an electrically short transmission antenna. Installed for LBA in the spring of 2009 by Guam contractor AIC International Construction, the antenna's propagation of medium wave signals has proven effective and efficient, though its physical footprint is much smaller than the three-tower system it replaced.

The SAMWAS antenna system is rated for 2,500 watts and incorporates a199-foot triangular grounded steel tower and proprietary radiating and tuning technology. The new antenna is stubby in comparison to conventional ¼ wave vertical NAVTEX antennas, yet provides similar broadcast coverage at much less cost. The antenna system operates at modest radio frequency voltages, yielding a more environmentally stable and broader bandwidth signal than a conventional series-fed tower of comparable height.

The relatively short tower avoids the need for aviation safety lights with associated installation and operating costs. Because it is grounded, the tower reduces system vulnerability to lightning and RF safety hazards. It was engineered by LBA Technology to withstand wind gusts of 170 mph.

The tower rises in a clearing in an otherwise verdant Guam landscape - with the transmitter building located fully 3,000 feet from the tower. Because AC power was not needed for tower lights, an existing coaxial cable was utilized and eliminated trenching and placement costs. LBA's Phantom-E™ remote control option uses the coax cable as its sole connection with the SAMWAS tower. The remote system both powers the circuitry in the tuning unit and selects between 490 and 518 kHz frequency modes.

As there are no moving RF parts in the tuning unit, it is expected to function reliably for years with minimal maintenance. The stability of the overall system means periodic retuning is not needed to accommodate changing environmental conditions.

Other SAMWAS antenna systems ranging in height from 65 to 350 feet are available to support DGPS, NAVTEX, and GMDSS medium wave transmissions. Dual NAVTEX frequency support and DGPS diplexing are options. LBA can perform as full turnkey contractor including installation of transmitters and message equipment.

For tactical communication situations, LBA Technology offers medium wave transmission systems integrated into trucks or trailers, and smaller emergency units that can be assembled on site by hand.

About LBA Technology, Inc.

LBA Technology is a leading manufacturer and integrator of radio frequency systems, components and test equipment for broadcast, industrial and government users worldwide. With consultant firm Lawrence Behr Associates, Inc., the company is a unit of the LBA Group, Inc., which has over 40 years experience in providing support for infrastructure assets of the wireless telecommunications industry. The companies are based in Greenville, NC.

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Dick Hansson
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