World's Most Powerful Radio Transmitter
February 1954 Radio & Television News

February 1954 Radio & TV News

[Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Radio & Television News, published 1919-1959. All copyrights hereby acknowledged.

In the early 1950s, the U.S. Navy built what was at the time the world's largest and most powerful radio broadcast (abbreviated "b.c.'" in the article) transmitter station at the Jim Creek Naval Station on Wheeler Mountain in Washington state. Its 1.2 MW, 24.8-to-35 kHz VLF transmitter (call sign NLK) can reach anywhere in the world, even to submarines. A half wavelength at 24.8 kHz is 19,830 feet. Photos indicate that the transmitter is located in the middle of a dipole arrangement. "Catenary cables," if you are unfamiliar with the term, refers to the sagging shape assumed by both the antenna cables and the tower support cables. "Catenary" stems from the word "chain," since it is the form a chain takes when suspended at both ends and allowed to hang freely in a gravitational field. The hyperbolic cosine function describes it mathematically. It is also the root of the word "concatenate," meaning to string together.

Having grown up just a few miles from the U.S. Navy's VLF transmitter station (NSS) in Annapolis, Maryland, I remember seeing the long arrays of tall towers with antenna cables strung between them. You can click on this Google Street View image to see what remains of the antenna farm on the north shore of the Severn River. There were many more towers back in the 1970s with a spider-web-looking maze of cables. In fact, a newspapers.com search turned up this 1999 public notice (thumbnail at left) to tear down 19 of the towers.

World's Most Powerful Radio Transmitter

Signals are so strong they may be received even by submerged subs.

The world's most powerful radio transmitter has been put into operation by the U.S. Navy at Jim Creek Valley, Washington, in the heart of the Cascade mountains.

The new 1,200,000-watt radio-telegraph transmitter can send messages to Navy forces operating in any of the seven seas and its signals will penetrate to submarines cruising below the surface as well as to arctic outposts despite frequent magnetic storms and ionospheric disturbances.

The megawatt transmitter has been designed around the special RCA Type 5831, 500 kw. high-vacuum triode. Each of the two power amplifiers employs three 5831's, two in the push-pull circuit with the third available as a spare.

The transmitter also features micro-second fault protection developed especially for this equipment. This electronic device relieves overload faults in the super-power amplifier tubes in seven-millionths of a second and prevents the build-up of currents that could damage the tubes.

Tuning adjustments have been confined to remote push-button control of the antenna and power amplifier tuning. This is accomplished by special broadband amplifiers developed by RCA and used in its standard b.c. transmitters.

The antenna is a highly-efficient catenary-type with ten catenary spans, representing the largest antenna ever erected.

The transmitter itself is contained in an enclosure 80 feet wide by 50 feet deep. The transmitter is arranged in "U" shape with the supervisory control console and the operator's desk located between the wings of the "U."

The windowless transmitter station is several stories high and is shielded against the intense electromagnetic field. The structure also includes a machine, electrical, sheet metal, and other servicing shops as well as storage space.

ARLINGTON, Wash. (Aug. 12, 2013) Lt. Gregory Carter, the officer in charge of Naval Radio Station Jim Creek (click to visit their Facebook page), talks about the rich history and current operations of the 60-year-old radio station. Established in 1953, the station is used to transmit radio messages to the U.S. Navy's Pacific Fleet and at the time of its activation was the largest radio transmitter in the world. The recreation area and interpretive center located on the Jim Creek site are also discussed.

(U.S. Navy video by Mass Communication Specialist 2nd Class Jeffry Willadsen with contributions from Mass Communication Specialists 1st Class Kyle Steckler, Robin Hicks, Lt. Gregory Carter and navy-radio.com)

The above video was discovered on the Navy-Radio.com website, which also has lots of other great information on the U.S. Navy's VLF radio installations.

Posted November 3, 2022
(updated from original post on 2/3/2016)