RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while typing up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
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and text used on the RF Cafe website are hereby acknowledged.
Wax nostalgic about and learn from the history of early
electronics. See articles from Radio & Television News, published 1919-1959. All copyrights hereby
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.
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.
View from transmitter building along the antenna lead-in trunk, shows 145 foot bus tower halfway up mountain, one of thirteen
which support transmission line. The "doughnuts" are corona shields guarding the trunk from damage by corona discharge.
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.
Bird's-eye view through steel framework of 200-foot summit ridge tower shows transmitter building nestling in valley between
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.
This frame from the above video shows how the antenna was strung through Wheeler Mountain.
Posted February 3, 2016
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