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
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.
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.
Bird's-eye view through steel framework of 200-foot summit ridge
tower shows transmitter building nestling in valley between 3000-foot mountains.
This frame from the imbedded video shows how the antenna was
strung through Wheeler Mountain.
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)
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