(electronics) Undesired oscillation in an amplifying system or transducer, usually of a pulse type, occurring at a subaudio or low-audio frequency.
motorboating
| Sci-Tech Dictionary: motorboating |
(′mōd·ər′bōd·iŋ)
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| Columbia Encyclopedia: motorboating |
motorboating, sport of navigating a motor-powered vessel on the water. It is done on either fresh- or saltwater and may be competitive or recreational. The first successful motorboat traveled (1887) a few yards on the Seine River in Paris. As the internal-combustion engine was improved, the motorboat became a practical means of transportation and motorboating became a popular sport. In 1903 the Harmsworth Trophy Race, one of the sport's most prestigious international competitions, was inaugurated in Great Britain. In the following year the Gold Cup Race, the premier U.S. competition, was first held.
Motorboating did not become widely popular until after World War II. Since then, however, it has grown tremendously, as greater affluence, increased leisure time, and mass production made it possible for more and more people to own motorboats. By 1996 there were estimated to be 12 million such boats in U.S. waters, and calls were increasing for stricter licensing and training of operators.
The smaller motorboats, traditionally called runabouts, range from 10 to 22 ft (3-6.7 m) in length; cabin cruisers, often equipped with facilities for cooking, dining, and sleeping, may be from 20 to 60 ft (6.1-18.3 m) long. The larger and more luxurious cabin cruisers are often called yachts.
Recreational boats are generally powered by a gasoline or diesel engine that turns a submerged propeller located behind the boat. Engines may be of either the outboard or inboard type. Outboard engines, generally found in smaller boats, are mounted at the back of the craft, which is steered by rotating the engine. The larger inboard-type vessels have their engine in the middle of the boat and are steered with a wheel-controlled rudder; the engine is attached to the propeller by a drive shaft beneath the craft. Certain classes of racing boats are jet-powered and are able to attain speeds of 250 mph (402 kph). The fastest propeller-driven racing boats can travel about 175 mph (282 kph).
Bibliography
See J. West, Modern Powerboats (1970); N. E. Fletcher and J. D. Ladd, Family Sports Boating (1972); E. A. Zadig, The Complete Book of Boating (1972).
| Wikipedia: Motorboating |
Motorboating is one of many problems that can afflict radio transmitters and similar devices. Radio transmitters are vulnerable to unwanted feedback; one possible symptom of unwanted feedback are rapid changes in power output, which repeats about 20 to 20,000 times per second; this is called motorboating because when the radio transmission is received, it resembles the sound of a motorboat engine.
Contents |
Technical description
Motorboating is a term for a self-inflicted EMC problem where Radio frequency (RF) from a device leaves through one route and then re-enters the unit through another conduit where it causes an increase in the level of the RF generated by the unit. When this RF output climbs above a given level a catastrophic change occurs which causes the RF power output to drop rapidly. This causes a series of audio frequency pulses to be generated, in an AM system these can be heard clearly as a sound which is like the engine of a motorboat.
In general, as the intended RF power output of the device is increased the possibility of motorboating is increased. If motorboating is occurring in a system then the rate of the low frequency oscillation will increase.
Theory
If an electronic device is considered as a black box whose output is related to a series of inputs by a mathematical function, then if one of the inputs to the device is leaking RF into the system then the output will be a function of the RF input.
If the RF leaks into the device which generates the RF it can alter the RF power output, it might cause an increase in the RF power level, which in turn leads to an increase of the effect which causes the effect increasing the RF output to increase. This, if unchecked, will lead to a greater and greater increase in power output.
Assuming that the device does not fail due to this power surge, then it is likely that the system will reach a state where it is either insensitive to any further increase in RF input (then the power increase will cease), or a sudden catastrophic change will occur to state where the RF power output is smaller. The second of these cases can lead to an oscillation.
Example
Imagine a 27 MHz CB radioset connected to an external 12 volt DC supply, if the decoupling capacitors which link the supply wires to the RF ground (case) are missing then it is possible for RF to enter the radio set through the supply wires. This then causes the motorboating to occur.
External links
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 | Sci-Tech Dictionary. McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/. Read more |
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