When the fog rolled in, making it difficult if not impossible for mariners to find landmarks and lighthouse beacons, Sea Girt Lighthouse was the first lighthouse in America to transmit radio signals to enable sailors to navigate in low visibility.
In 1921, the U.S. Lighthouse Service chose Sea Girt to be the first land-based light station in America equipped with a radio fog beacon transmitter that broadcast guiding signals that could be heard by ships up to 100 miles away. It began transmitting May 1 of that year. Transmitters were also installed aboard Ambrose Channel Lightship in Lower New York Bay off Sandy Hook and Fire Island Lightship off Long Island.
“The stations are identified by the characteristics of the signal, thus Ambrose Channel sends one dash, Fire Island a group of two dashes and Sea Girt a group of three dashes, with brief intervals between the groups,” explained the U.S. Lighthouse Service at the time.
Ships anywhere within range of the radio beacons could navigate by triangulation – tracking the three signals to fix their own position. “This system, for the first time in navigation, affords a practicable means by which the navigator can take reasonably accurate bearings on fixed beacons which are not visible,” stated the U.S. Lighthouse Service.
Cannon Balls and Whistles
The first fog signal in America was sounded in 1719 at Boston Light in 1719, where a cannon was fired once every hour during fog. In time many other lighthouses were equipped with cannons, as well as whistles, horns, sirens and bells to be used by the keeper to warn ships away from fog-shrouded shoals and the shore.
The radio fog beacon system, a vast improvement over previous generations of audible systems, was an outgrowth of research done before World War I. In 1915-16 the Bureau of Standards was working on improvements of radio compasses. In 1917, the Bureau of Standards and the Lighthouse Service experimented with a radio transmitter at Navesink Twin Lights that sent signals to a radio compass receiver on a lightship miles offshore. Further work was put on hold during World War I but resumed afterwards with encouraging test results at three lighthouses in Chesapeake Bay.
Upon the successful deployment of the first radio fog beacon system at Sea Girt, Ambrose and Fire Island, other triangulating networks were then installed along the Atlantic Coast, Great Lakes and Pacific Coast. Within a decade there were 90 stations transmitting radio fog beacons. Where fog beacons were not installed, audible warning devices remained in use.
The need for the radio fog beacon system was underscored by a 1923 survey of New England and West Coast lighthouses which reported foggy conditions anywhere from 11% to 19% of the period covered by the survey.
Sea Girt Transmitter
The fog transmitter at Sea Girt was installed in the spring of 1921. “The transmitting apparatus now in use is a commercial panel-type transmitting set of simple and rugged construction of about 1-kilowatt power. In addition to this set a special automatic motor-driven timing switch for producing the desired signal at regular intervals is provided,” stated the Lighthouse Service.
“The antennas are the same as used for ordinary radio communication,” noted the Service. “The range of usefulness varies from 30 to 100 miles, depending upon the sensitivities of the receiving apparatus.” In contrast, lighthouse beacons, depending on the size of the lens, can be seen in good weather at distances between 12 and 21 miles. The antennas at Sea Girt were atop 60-foot-high metal skeleton towers – taller than the lighthouse itself. The towers stood on southeast and northwest corners of the property.
“No, I am not a radio operator,” noted William H.H. Lake, then Sea Girt’s light keeper, explaining the system to The Asbury Park Press. “One doesn’t have to be a radio man to operate the range signal apparatus. It is all automatic.”
The 1923 annual report of the Lighthouse Service stated: “The signals are operated continuously during thick or foggy weather, and also at the present time they are sent each day from 9 to 9:30 a.m., and from 3 to 3:30 p.m., so as to permit any vessel equipped with radio compass to try out the method and apparatus in clear weather.”
To help mariners distinguish one station from another, the Lighthouse Service and the Coast Guard published annual chart books such List of Lights and Fog Signals that listed and described the “characteristics” of each station’s light beam, the appearance of the lighthouse structure, and – if it had a fog beacon – the unique sequence of its transmission.
Sea Girt’s radio signal was changed by the Lighthouse Service after two years. “On April 23, 1923 the characteristic of the radio fog signal at Sea Light Station was changed from 3 dashes for 60 seconds, silent six minutes to 3 dashes for 30 seconds, silent three minutes,” announced Lighthouse Superintendent J.T. Yates.
The radio fog beacon continued to transmit from Sea Girt Lighthouse until 1928 when it was transferred to Barnegat Lighthship.
The towers were finally removed in late 1931 – not long after the arrival of a new keeper – on the orders of the Lighthouse Service. While nothing remains, the seven years the radio fog beacon system operated established Sea Girt Lighthouse as a pioneer in navigation.