Percy Spencer

Last updated
Percy Spencer
BornJuly 19, 1894
DiedSeptember 8, 1970(1970-09-08) (aged 76)
Education United States Navy
Employer Raytheon
Known for Microwave oven
Spouse(s)Louise Spencer, Lillian Ottenheimer Spencer
ChildrenJames, John, and George

Percy Lebaron Spencer (July 19, 1894 – September 8, 1970) was an American physicist and inventor. He became known as the inventor of the microwave oven. [1]

United States Federal republic in North America

The United States of America (USA), commonly known as the United States or America, is a country comprising 50 states, a federal district, five major self-governing territories, and various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is slightly smaller than the entire continent of Europe. With a population of over 327 million people, the U.S. is the third most populous country. The capital is Washington, D.C., and the most populous city is New York City. Most of the country is located contiguously in North America between Canada and Mexico.

Physicist scientist who does research in physics

A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate causes of phenomena, and usually frame their understanding in mathematical terms. Physicists work across a wide range of research fields, spanning all length scales: from sub-atomic and particle physics, through biological physics, to cosmological length scales encompassing the universe as a whole. The field generally includes two types of physicists: experimental physicists who specialize in the observation of physical phenomena and the analysis of experiments, and theoretical physicists who specialize in mathematical modeling of physical systems to rationalize, explain and predict natural phenomena. Physicists can apply their knowledge towards solving practical problems or to developing new technologies.

An inventor is a person who creates or discovers a new method, form, device or other useful means that becomes known as an invention. The word inventor comes from the Latin verb invenire, invent-, to find. The system of patents was established to encourage inventors by granting limited-term, limited monopoly on inventions determined to be sufficiently novel, non-obvious, and useful. Although inventing is closely associated with science and engineering, inventors are not necessarily engineers nor scientists.


Early life

Spencer was born in Howland, Maine. Eighteen months later, Spencer's father died, and his mother soon left him in the care of his aunt and uncle. His uncle then died when Spencer was just seven years old. Spencer subsequently left grammar school to earn money to support himself and his aunt. From the ages of twelve to sixteen, he worked from sunrise to sunset at a spool mill. At the later age, he discovered that a local paper mill was soon to begin using electricity, a concept little known in his rural home region, and he accordingly began learning as much as possible about the phenomenon. Therefore, when he applied to work at the mill, he was one of three people hired to install electricity in the plant, despite never having received any formal training in electrical engineering or even finishing grammar school. At the age of 18, Spencer decided to join the U.S. Navy. He had become interested in wireless communications after learning about the wireless operators aboard the Titanic when it sank. While he was with the navy, he made himself an expert on radio technology: "I just got hold of a lot of textbooks and taught myself while I was standing watch at night." He also subsequently taught himself trigonometry, calculus, chemistry, physics, and metallurgy, among other subjects. [1] [2]

Howland, Maine Town in Maine, United States

Howland is a town in Penobscot County, Maine, United States, which was settled in 1818. It was named after John Howland, one of the passengers on the Mayflower. The population was 1,241 at the 2010 census.

Grammar school type of school in the United Kingdom and some other countries

A grammar school is one of several different types of school in the history of education in the United Kingdom and other English-speaking countries, originally a school teaching Latin, but more recently an academically-oriented secondary school, differentiated in recent years from less academic secondary modern schools.

Paper mill factory that produces paper

A paper mill is a factory devoted to making paper from vegetable fibres such as wood pulp, old rags and other ingredients. Prior to the invention and adoption of the Fourdrinier machine and other types of paper machine that use an endless belt, all paper in a paper mill was made by hand, one sheet at a time, by specialized laborers.


By 1939 Spencer became one of the world’s leading experts in radar tube design. Spencer worked at Raytheon, a contractor for the U.S. Department of Defense, as the chief of the power tube division. Largely due to his reputation and expertise, Spencer managed to help Raytheon win a government contract to develop and produce combat radar equipment for M.I.T.’s Radiation Laboratory. This was of huge importance to the Allies and became the military’s second highest priority project during WWII, behind the Manhattan Project. At that time, magnetrons were used to generate the microwave radio signals that are the core mechanism of radar, and they were being made at the rate of 17 per day at Raytheon. While working there, Spencer developed a more efficient way to manufacture them, by punching out and soldering together magnetron parts, rather than using machined parts. It also saw Spencer’s staff rise from 15 employees to 5,000 over the course of the next few years. His improvements were among those that increased magnetron production to 2,600 per day. For his work, he was awarded the Distinguished Public Service Award by the U.S. Navy. [2]

Radar object detection system based on radio waves

Radar is a detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna and a receiver and processor to determine properties of the object(s). Radio waves from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed.

Raytheon American industrial corporation

The Raytheon Company is a major U.S. defense contractor and industrial corporation with core manufacturing concentrations in weapons and military and commercial electronics. It was previously involved in corporate and special-mission aircraft until early 2007. Raytheon is the world's largest producer of guided missiles. On June 9, 2019, Raytheon announced a merger of equals with the aerospace companies of United Technologies.

United States Department of Defense United States federal executive department

The United States Department of Defense is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national security and the United States Armed Forces. The DoD is the largest employer in the world, with nearly 1.3 million active-duty service members as of 2016. More employees include over 826,000 National Guard and Reservists from the armed forces, and over 732,000 civilians bringing the total to over 2.8 million employees. Headquartered at the Pentagon in Arlington, Virginia, just outside Washington, D.C., the DoD's stated mission is to provide "the military forces needed to deter war and ensure our nation's security".

One day while building magnetrons, Spencer was standing in front of an active radar set when he noticed the candy bar he had in his pocket had melted. Spencer was not the first to notice this phenomenon, but he was the first to investigate it. He decided to experiment using food, including popcorn kernels, which became the world’s first microwaved popcorn. In another experiment, an egg was placed in a tea kettle, and the magnetron was placed directly above it. The result was the egg exploding in the face of one of his co-workers, who was looking in the kettle to observe. Spencer then created the first true microwave oven by attaching a high-density electromagnetic field generator to an enclosed metal box. The magnetron emitted microwaves into the metal box blocking any escape, allowing for controlled and safe experimentation. He then placed various food items in the box, while observing effects and monitoring temperatures.

Candy bar type of sugar confectionery that is in the shape of a bar

A candy bar is a type of sugar confectionery that is in the shape of a bar.

Popcorn A variety of corn kernel, which expands and puffs up when heated

Popcorn is a variety of corn kernel, which expands and puffs up when heated.

Kettle appliance for boiling water

A kettle, sometimes called a tea kettle or teakettle, is a type of pot, specialized for boiling water, with a lid, spout, and handle, or a small kitchen appliance of similar shape that functions in a self-contained manner. Kettles can be heated either by placing on a stove, or by their own internal electric heating element in the appliance versions.

Raytheon filed a patent on October 8, 1945 for a microwave cooking oven, eventually named the Radarange. In 1947, the first commercially produced microwave oven was about 6 feet tall, weighed about 750 lbs, and cost about 5,000 US$. In 1967 the first relatively affordable ($495) and reasonably sized (counter-top) microwave oven was available for sale. [2]

Patent Intellectual property conferring a monopoly on a new invention

A patent is a form of intellectual property that gives its owner the legal right to exclude others from making, using, selling, and importing an invention for a limited period of years, in exchange for publishing an enabling public disclosure of the invention. In most countries patent rights fall under civil law and the patent holder needs to sue someone infringing the patent in order to enforce his or her rights. In some industries patents are an essential form of competitive advantage; in others they are irrelevant.

Microwave oven kitchen appliance

A microwave oven is an electric oven that heats and cooks food by exposing it to electromagnetic radiation in the microwave frequency range. This induces polar molecules in the food to rotate and produce thermal energy in a process known as dielectric heating. Microwave ovens heat foods quickly and efficiently because excitation is fairly uniform in the outer 25–38 mm(1–1.5 inches) of a homogeneous, high water content food item.

Spencer became Senior Vice President and a Senior Member of the Board of Directors at Raytheon. He received 300 patents during his career, and a building at the Raytheon Missile Defense Center in Woburn, Massachusetts is named in his honor. Other achievements and awards, besides the Distinguished Public Service Award, included a membership of the Institute of Radio Engineers, Fellowship in the American Academy of Arts and Sciences, and an honorary Doctor of Science from the University of Massachusetts, despite having no formal education.

Woburn, Massachusetts City in Massachusetts, United States

Woburn is a city in Middlesex County, Massachusetts, United States. The population was 38,120 at the 2010 census. Woburn is located 9 miles (14 km) north of Boston, Massachusetts.

The Institute of Radio Engineers (IRE) was a professional organization which existed from 1912 until December 31, 1962. On January 1, 1963 it merged with the American Institute of Electrical Engineers (AIEE) to form the Institute of Electrical and Electronics Engineers (IEEE).

American Academy of Arts and Sciences United States honorary society and center for independent policy research

The American Academy of Arts and Sciences is one of the oldest learned societies in the United States. Founded in 1780, the Academy is dedicated to honoring excellence and leadership, working across disciplines and divides, and advancing the common good.

For his invention, Spencer received no royalties, but he was paid a one-time $2.00 gratuity from Raytheon, the same token payment the company made to all inventors on its payroll at that time for company patents. [3]

Personal life

Spencer and his wife, Louise, had three children: John, James, and George. He counted Vannevar Bush, Omar Bradley, William Redington Hewlett and David Packard as friends. Later, he was married to Lillian Ottenheimer on November 18, 1960.


Raytheon Integrated Defense Systems, which deals extensively in radar systems, has named a building after Spencer in the Woburn, Massachusetts facility. An early Radarange model sits in the lobby, across from the dining center.

Related Research Articles

Cavity magnetron device for generating microwaves

The cavity magnetron is a high-powered vacuum tube that generates microwaves using the interaction of a stream of electrons with a magnetic field while moving past a series of open metal cavities. Electrons pass by the openings to these cavities and cause radio waves to oscillate within, similar to the way a whistle produces a tone when excited by an air stream blown past its opening. The frequency of the microwaves produced, the resonant frequency, is determined by the cavities' physical dimensions. Unlike other vacuum tubes such as a klystron or a traveling-wave tube (TWT), the magnetron cannot function as an amplifier in order to increase the intensity of an applied microwave signal; the magnetron serves solely as an oscillator, generating a microwave signal from direct current electricity supplied to the vacuum tube.

Texas Instruments American semiconductor designer and manufacturer

Texas Instruments Incorporated (TI) is an American technology company that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globally. Its headquarters are in Dallas, Texas, United States. TI is one of the top-10 semiconductor companies worldwide, based on sales volume. Texas Instruments's focus is on developing analog chips and embedded processors, which account for more than 80% of their revenue. TI also produces TI digital light processing technology and education technology products including calculators, microcontrollers and multi-core processors. To date, TI has more than 45,000 patents worldwide.

Oven thermally insulated chamber used for the heating, baking or drying of a substance

An oven is a thermally insulated chamber used for the heating, baking, or drying of a substance, and most commonly used for cooking. Kilns and furnaces are special-purpose ovens used in pottery and metalworking, respectively.

Ivan Alexander Getting was an American physicist and electrical engineer, credited with the development of the Global Positioning System (GPS). He was the co-leader of the research group which developed the SCR-584, an automatic microwave tracking fire-control system, which enabled anti-aircraft guns to destroy a significant percentage of the German V-1 flying bombs launched against London late in the Second World War.

History of radar aspect of history

The history of radar started with experiments by Heinrich Hertz in the late 19th century that showed that radio waves were reflected by metallic objects. This possibility was suggested in James Clerk Maxwell's seminal work on electromagnetism. However, it was not until the early 20th century that systems able to use these principles were becoming widely available, and it was German inventor Christian Hülsmeyer who first used them to build a simple ship detection device intended to help avoid collisions in fog. Numerous similar systems, which provided directional information to objects over short ranges, were developed over the next two decades.

Robert Noel Hall was an American engineer and applied physicist. He demonstrated the first semiconductor laser and invented a type of magnetron commonly used in microwave ovens. He also contributed to the development of rectifiers for power transmission.

Microwave popcorn

Microwave popcorn is a convenience food consisting of unpopped popcorn in an enhanced, sealed paper bag intended to be heated in a microwave oven. In addition to the dried corn, the bags typically contain cooking oil with sufficient saturated fat to solidify at room temperature, one or more seasonings, and natural or artificial flavorings or both. With the many different flavors, there are many different providers.

William C. Brown was an American electrical engineer who helped to invent the crossed-field amplifier in the 1950s and also pioneered microwave power transmission in the 1960s.

Robert Vincent Decareau was an American food scientist who was involved in the development of microwave applications in food technology, specifically technology that would lead to the development of the microwave oven. He also served in the United States Navy during World War II and in the United States Army during the Korean War. Decareau also was charter member of Phi Tau Sigma while pursuing his Ph.D. at the University of Massachusetts Amherst.

The Radiation Laboratory, commonly called the Rad Lab, was a microwave and radar research laboratory located at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts (US). It was first created in October 1940 and operated until 31 December 1945 when its functions were dispersed to industry, other departments within MIT, and in 1951, the newly formed MIT Lincoln Laboratory.

International Home + Housewares Show

The International Home + Housewares Show is staged every year by the International Housewares Association (IHA). It is the center of the IHA's yearly activities. In 2008, the Show covered 785,000 net square feet (72,900 m2) of exhibit space. It is one of top 20 largest trade shows in the U.S. and in the top 10 in Chicago.

Kinjiro Okabe was a Japanese electrical engineering researcher and professor who made major contributions to magnetron and radar development. He did work after the Second World War on medical instruments using ultrasounds.

Rudolf Kühnhold (1903–1992) was an experimental physicist who is often given credit for initiating research that led to the Funkmessgerät in Germany.

Sir John Turton Randall, was an English physicist and biophysicist, credited with radical improvement of the cavity magnetron, an essential component of centimetric wavelength radar, which was one of the keys to the Allied victory in the Second World War. It is also the key component of microwave ovens.

Microwave engineering pertains to the study and design of microwave circuits, components, and systems. Fundamental principles are applied to analysis, design and measurement techniques in this field. The short wavelengths involved distinguish this discipline from Electronic engineering. This is because there are different interactions with circuits, transmissions and propagation characteristics at microwave frequencies.

John G. Trump American engineer and physicist

John George Trump was an American electrical engineer, inventor, and physicist. A professor at the Massachusetts Institute of Technology from 1936 to 1973, he was a recipient of U.S. President Ronald Reagan's National Medal of Science and a member of the National Academy of Engineering. John Trump was noted for developing rotational radiation therapy. Together with Robert J. Van de Graaff, he developed one of the first million-volt X-ray generators. He was the paternal uncle of Donald Trump, who would later go on to become the 45th president of the United States.

Anaren, Inc. provides high-frequency microwave microelectronics, components, and assemblies for wireless, aerospace, and defense electronics applications.


  1. 1 2 "Inventors Hall of Fame" . Retrieved 30 November 2012.
  2. 1 2 3 "Inventor of Microwave Oven" . Retrieved 30 November 2012.
  3. "NNDB Noteworthy Name Database Historical Facts" . Retrieved 30 November 2012.