History of the US Coast Guard coastal navigation radio beacons

[Radio KH6O]

Before GPS, recreational, commercial, and military vessels relied upon low-power, fixed location radio beacons for coastal navigation. These transmitters operated in the 300-400 kHz band. Each beacon transmitted a unique Morse code identifier (e.g., Point Sur along the central California coast sent "PS" in Morse). 

Reception of these beacons was usually done using a direction-finding receiver. Using a DF receiver, the operator would determine the bearing of at least two beacons, locate them on his navigation chart (via the beacon's unique frequency and identifier), and draw the bearing lines; where the lines crossed marked his location. Ideally, at least 3 beacon bearings would be determined for a more accurate fix. 

Rarely, the 3 bearing lines crossed at a single point -- instead they would form a triangle, what navigators called a "Cocked Hat." 

This was a very simple, reliable, and low-cost navigational system.

While stationed at US Coast Guard Station Monterey as a radioman (RM), I frequently accompanied the electronics technicians (ET) to the Point Pinos lighthouse. The radio beacon at that site sent "P" as its identifier via a code wheel. 

Here is a typical portable DF receiver that could be found on most pleasure vessels (note the rotatable magnetic loop antenna on top):

https://www.worthpoint.com/worthopedia/coastal-navigator-direction-finder-489125338

Here is the History and Status of the US Marine Radio Beacon System, dated 1982:

https://apps.dtic.mil/sti/tr/pdf/ADA125461.pdf

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Jeff KH6O / 6