Editorial
Wanted—Present Terms
Our editorial of last month “Wanted – New Terms” seems to have touched several tender spots. From letters which have come in, the consensus of opinion seems to be that there is a more immediate need for the standardization of “present” terms – while the field is still young – rather than confining our efforts to new terms. As a result, we are reprinting the available lists of definitions as used by the Air Force and Signal Corps, together with a list kindly submitted by the Radio Interference Laboratories of the Burroughs Corporation and reference to the Institute of Radio Engineers (IRE) Standards.
Several correspondents suggested that we try to get a Discussion Group together to talk this – and other problems in the Interference Field—over. We would like to make an additional suggestion that Area Groups be organized—for the East, Middle-West and Pacific Coast—in order to broaden the viewpoints. The recommendations of these Groups could then be collated and the results presented to the IRE for inclusion in any definitions which they might contemplate for the Interference Field.
We would be very glad to attempt to start such Groups and would welcome hearing from those who would like to serve – and suggestions as to who might act as temporary chairman of each. It will, of course, require time and effort on the parts of those interested but, on the other hand, the effort would be most valuable and rewarding.
There will be new problems constantly being put up to these Groups, many of which manufacturers will be most interested in. Take, for example, the problem which would seem to be facing the Metal Textile Corporation, makers of electronic weather-stripping and RF gaskets.
In their new brochure “Suppressing Radio Interference with Metex Electronic Weather-strips and RF Gaskets,” they have used the term “Insertion Loss” to describe the db attenuation resulting from the use of their shielding products. This is truly an applicable descriptive term in as much as it gives a measure of the amount of loss which can be expected when a voltage on one side of the shielding is referred to the voltage on the other side. However, it can be confusing to a person – not well versed in the art when he looks up the definition of the term – who finds only reference to filters and condensers. This leads to the conclusion that the definition of “insertion loss” should be broadened to include the above-mentioned category or others which may fall in with the idea of loss of voltage when passing through a medium – or a new term should be coined to include all these cases, exclusive of filters and condensers.
As another example, the term “impedance” is normally used to define that which retards the flow of alternating current, whereas the term “resistance” is normally used to describe that which retards the flow of direct current. It appears that our present definition should take into account the type of current which is flowing when we describe the term “impedance.” Burroughs comes closest to it.
We would appreciate hearing from you as to whether something should be done.
Articles of Interest—from the Journal
of Applied Physics
January 1955:
Measurements of Electrical Polarization in Thin Dielectric Materials, by R.W. Tyler, J.H. Webb, and W.C. York; Research Laboratories, Eastman Kodak Company, Rochester, N.Y.
Relaxation Oscillations and Noise from Arc Discharge, by M.I. Skolnik and H.R. Puckett, Jr.; Radiation Laboratory, The Johns Hopkins University, Baltimore, Md.
February 1955:
Radiation of Plasma Noise from Arc Discharge, by T. Takakura, K.Baba, K. Nunogaki and H. Mitani; Osaka City University, Kitaku, Osaka, Japan.
Short-Time Frequency Measurement of Narrow-Band Random Signals by Means of a Zero Counting Process, by H. Steinberg, P.M. Schultheiss, C.R. Wogrin and F. Zweig; Dunham Laboratory of Electrical Engineering, Yale University, New Haven, Conn.
March 1955:
Barkhausen Noise from a Cylindrical Core, by D.Haneman; University of Sydney, Sydney, Australia.
April 1955:
Theory of Frequency Modulation Noise in Tubes Employing Phase Focusing, by John L. Stewart; Department of Electrical Engineering, University of Michigan, Ann Arbor, Mich.
Variation of Noise with Ambient in Germanium Filaments by T.J. Maple, L. Bess and H.A.Gebbie; Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, Mass.
May 1955:
Noise in One-Dimensional Electron Beams, by Herman A. Haus; Research Laboratory of Electronics, M.I.T., Cambridge, Mass.
Arcing at Electrical Contacts on Closure, Part VI, The Anode Mechanism of Extremely Short Arcs, by W.S. Boyle and L.H. Germer,
Noise at the Potential Minimum in the High-Frequency Diode, by D.A. Watkins; Stanford University, Stanford, Calif.
Papers to be given:
1955 Toronto Meeting of American Physical Society, June 22–24, 1955:
U8. Noise Characteristics of Silicon Photovoltaic Junctions, by U.F. Gianola; Bell Telephone Laboratories.
U11. Noise Fluctuations and Irreversible Processes, by D.L. Falkoff; Brandeis University, Waltham, Mass.
Glossary of Radio-Interference Terms
(The following glossary of interference terms is submitted by Sylvester Pelowski, Burroughs Corp. Radio Interference Laboratories, due to “the necessity of defining terms to non-initiated personnel.”)
Ambient Interference. The interference level resulting from sources other than that being measured. This includes atmospherics, man-made interference and the internal noise of the measuring set.
Bond. An electrical path of low impedance at radio frequencies.
Bulkhead-Mounted Filter. A filter which is installed so that a metal wall isolates the filter input terminals from the filter output terminals.
Conducted Interference. Interference transmitted along an electrical conductor.
Feed-Through Condenser. A condenser with capacity between a metal case and a lead passing through the case; effectively, a lead-less container.
Field-Intensity Value of Interference. Interference measured in terms of its average value.
Filter. A network which reduces the amount of radio interference transmitted away from the interference source by current-carrying conductors. Usually a configuration of condensers and inductors enclosed in a single container.
Frequency. The number of cycles completed each second.
Ground. A chassis, housing or other equipotential system used as a reference potential.
Ground Plane. A large copper plate that is bonded to the earth or screen room shielding. Used as a voltage reference level for interference measurements taken in a screen room.
Impedance. The opposition to current flow that is offered by an electrical path at a particular frequency.
Impedance Stabilization Network. A network which properly terminates the radio-interference measuring set cable at the line where conducted interference is being measured and isolates the effect of the screen room filter.
Impulsive Interference. Discontinuous interference consisting of sharp pulses which are relatively infrequent and clearly separated.
Indicated Microvolts. The interference measurement that is given by the radio-interference measuring set before conversion to standard units.
Internal Noise of Meter. A very low interference level originating in the circuit of the radio-interference measuring set.
Kilocycle (kc). A frequency of a thousand cycles per second.
Megacycle (Mc). A frequency of a million cycles per second.
Metal-to-Metal Contact. Intimate contact between two metallic surfaces with no non-conducting layer such as paint, corrosion, or anodized surfaces, separating them.
Microvolt. One millionth of a volt.
Peak Value of Interference. Interference measured in terms of its maximum value.
Quasi-Peak Value of Interference. Interference measured in terms of a value weighted to indicate the nuisance effect of interference.
Radiated Interference. Interference measured in terms of a valued weighted to indicate the nuisance effect of interference.
Radio Interference. An electrical disturbance which can affect the satisfactory operation of electrical or electronic equipment.
Radio-Interference Measuring Set. A highly sensitive radio receiver of special design which is calibrated and operated as a radio-frequency voltmeter at various frequencies.
Radio Interference Tests. Measurements conducted in an area of low ambient interference to determine how the magnitude of interference from a test item varies over a range of frequencies.
Screen Room. An area enclosed by shielding where the ambient interference is at a very low level, usually less than one microvolt per meter.
Shield. A metallic structure which reduces the radiated interference leaving or entering a specified region.
Shielded Cable. One or more insulated conductors enclosed by shielding.
Trace. An interference measurement too small for an accurate scale reading.
Definitions
From: Radio Interference Suppression Techniques, Coles Signal Laboratory, Fort Monmouth, New Jersey, pages 222–224.
Application Approved Suppression Component. Any capacitor, filter, etc., not covered in all respects by applicable subsidiary specifications having been properly submitted to and approved by the designated agency for a specific suppression application.
Battery Timer. A distributor and ignition coil combined physically as a single shielded electrical subassembly.
Bond. A low-impedance connection between two points.
Bonding. The process of connecting two points through a low-impedance path.
Conducted Interference. Radio-interference transmitted through metallic leads.
Corona Discharge. A high-voltage discharge between a conductor and the surrounding atmosphere.
Decibel. A unit of the ratio of two powers. The ratio of powers, P1 and P2, in decibels is equal to 10 log10(P1/P2).
Effective Bandwidth. The area divided by the Peak Height of the voltage-versus-frequency curve, measured from antenna to peak detector.
Electrical Accessory Unit. Any electric motor or electro-mechanical device, such as electric windshield wipers, electric heaters, relay mechanisms, etc., capable of operation independent of the unit or its electrical subassemblies except for the power source, and which is not associated with the basic functioning of the equipment.
Electrical Subassembly. Any engine or engine generator electrical sub-assembly such as spark plugs, generator, regulator, distributor, etc., associated with the basic functioning of the unit or its electrical system, which is supplied, stored and issued as a complete operating assembly.
Energy Spectrum. The energy-versus-frequency curve of any disturbance.
Faraday Shield. An electrostatic shield between the windings of a transformer.
Filter. A network designed to freely transmit currents or voltages of certain frequencies while attenuating all others.
Ground. A point of “zero” or “reference” potential, equipotential with all other ground points of the system such as frame, housing, chassis, etc.
Harmonic. A sinusoidal component of a periodic quantity whose frequency is an integral multiple of the fundamental frequency.
Ignitor. See: Battery Timer.
Impedance. The ratio of voltage to current.
Insertion Loss. The ratio of the voltage across a load impedance before and after insertion of the network under test.
Interference-Free Area. A test site suitable for radio-interference investigations, 1200 feet or more from buildings, trees, power and communication lines, underground cables, and similar natural or man-made obstructions.
Laboratory Tests. Radiated or conducted radio-interference measurements or a test item in a screened laboratory room or confined area of low ambient interference under controlled conditions.
Microvolt per kilocycle. Interference intensity in microvolts per kilocycle is equal to the number of rms sinewave microvolts (unmodulated), applied to the input of the measuring circuit at its center frequency, which will result in peak response in the circuit equal to that resulting from the interference pulse being measured, divided by the effective bandwidth of the circuit in kilocycles.
Microvolt per Megacycle. Interference intensity in microvolts per megacycle is equal to the number of rms sinewave microvolts (unmodulated), applied to the input of the measuring circuit at its center frequency, which will result in peak response in the circuit equal to that resulting from the interference pulse being measured, divided by the effective bandwidth of the circuit in megacycles.
Non-Sinusoidal Wave. A wave whose form differs from that of a sine wave and which hence contains harmonics.
Parasitic Oscillations. Unintended self-sustaining oscillations at a frequency different from the operating frequency or its harmonics or outside a tank circuit.
Radio Interference. Any electrical disturbance which causes undesirable response or malfunctioning in any receiver.
Shield. A metallic enclosure surrounding a source of interference or a circuit sensitive to interference.
Suppression. The reduction of interference by means applied to or at the source.
Suppression System. All components, materials, and their application used for suppression of radio interference.
Transient. A disturbance of short duration during an interval of readjustment of current or voltage in a circuit.
Type Approved Suppression Component. A component for which samples of the same make and type have previously been submitted and tested and approved as being suitable for suppression purposes in accordance with the applicable subsidiary specification.
Undesirable Response. Any audible, visible, or otherwise measurable response of a receiver not produced by a desired signal, provided that either its duration is longer than ten seconds or its highest recurrence rate is great than once every sixty seconds.
Institute of Radio Engineers (IRE) –
Definitions – Index
Master Index of IRE Definitions, Issue 3, February 1953.
“…It covers all terms which have been defined and standardized by IRE and all terms which are presently in the process of being defined. The list is intended for distribution to all members of the IRE technical committees and its main purpose is to form a quick reference for members who are working on definitions. It will be made available also to Definitions committees of other societies such as AIEE, ASA, etc.”
List of the IRE Standards which are available in printed form – selected subjects.
52 IRE 17.S1 Standards on Receivers: Definitions of terms, 1952 Reprinted from the December 1952, Proceedings $0.60
51 IRE 20.S1 Standards on Pulses: Definitions of Terms – Part I, 1951 Reprinted from June 1951, Proceedings $0.50
52 IRE 20.S1 Standards on Pulses: Definitions of Terms – Part II, 1952 Reprinted from the May 1952, Proceedings $0.50
48 IRE 21.S1 Standards on Abbreviations, Graphical Symbols, Letter Symbols, and Mathematical Signs, 1948 $0.75
49 IRE 21.S1 Standards on Designations for Electrical, Electronic, and Mechanical Parts and their Symbols, 1949 Reprinted from February 1950, Proceedings $0.60
51 IRE 21.S1 Standards on Abbreviations of Radio-Electronic Terms, 1951 Reprinted from April 1951, Proceedings $0.50
50 IRE 8.S1 Standards on Electronic Computers: Definitions of Terms, 1950 Reprinted from March 1951, Proceedings $0.75
Definitions
From: Design Techniques for Interference-Free Operation of Airborne Electronic Equipment, U.S. Air Force, Wright Air Development Center, Wright-Patterson Air Force Base, Dayton, Ohio. Appendix II.
Atmospheric Disturbances. Interference generated by thunderstorms and similar electronic disturbances.
Blooming. The destruction of focus on visual indicator caused by excessive beam intensity.
Break Transient. Transients produced by the opening of a switch.
Characteristic Impedance. The ratio of voltage to current along a transmission line on which no reflected wave is present.
Conducted Interference. Any interference transmitted through metallic leads.
Corona Discharge. A high voltage discharge occurring at the surfaces of conductors, accompanied by bluish-reddish light.
Coupling Factor (referring to receivers). The ratio of antenna input voltage to the voltage input required at the various coupling paths to produce the same output.
Decibel. A measure of the ratio of two powers. Power ratio (decibels) is equal to 10 log10 P1/P2
Depth of Penetration. The distance from the surface of a metal at which and electromagnetic wave or current has decreased to l/e times its value at the surface.
Dielectric Strength. The ratio of breakdown voltage to the thickness of the dielectric between contacts.
Faraday Shield. Is a set of grounded metallic prongs, somewhat like the teeth of a comb, placed between two coils for the prevention of capacitive coupling.
Ferrites (Ferrospinels). Mixtures of crystalline iron oxides of ceramic like structure.
Field Fixes. The modification of existing equipment and installations to insure comparative freedom from radio interference.
Field Tests. Are those conducted in an “open space” under actual operating and load conditions. Tests of conducted interference performed at the actual site of permanent installation meet the requirements of Field Tests.
Filter. A four-terminal network designed to freely transmit currents or voltages of certain frequencies while attenuating all others.
Frequency Translation. The production of new frequencies in a non-linear element.
Ground. A point of “zero” or “reference” electrical potential, often used in the following sense: (1) To connect to the aircraft structure through a low impedance path, (2) To make equipotential with all other “ground points” in the system.
Impedance Concept. Consideration of impedance as the ratio of cause to effect leads to the idea which regards the entire aircraft as a single network.
Impedance (referring to networks). The ratio of voltage to current.
Impedance (referring to media). The ratio of electric to magnetic field intensity.
Improvement Threshold. The minimum signal-to-interference ratio necessary at the input to produce an intelligible signal at the output.
Insertion Loss. The amount, usually expressed in decibels, by which the current in a transmission line, on the load side of the network, has been changed by the insertion of the network.
Interference-Voltage Reduction Factor. The ratio of the signal-to-interference ratio at the output to that as the input of a receiver.
Intrinsic Impedance. The ratio of electric to magnetic field intensity in a medium in which no reflected wave is present.
Laboratory Tests. Are measurements of radiated or conducted radio interference in which the test item is placed in a screened laboratory room or in a confined area of low ambient interference under controlled conditions.
Major Unit. In an assembly of parts, connected mechanically or electrically, such as a radar transmitter or a power pack, to perform a specific function.
Microvolts per kc. Interference intensity in microvolts per kc is equal to the number of r.m.s. sine wave microvolts (unmodulated), applied to the input of the measuring circuit at its center frequency, which will result in peak response in the circuit equal to that resulting from the interference pulse being measured, divided by the effective bandwidth of the circuit in kilocycles. The effective bandwidth is the area divided by the height, of the voltage-response-versus-radio-frequency selectivity curve, from antenna to peak detector.
Mismatch Ratio. The ratio of impedances looking to the right and to the left of the pair of terminals.
Non-linear Impedances. Impedances that vary with current through them or voltage across them.
Open Space. In a site ideally in open, flat terrain, 100 feet or more from buildings, trees, power lines or communication lines, underground cables and similar obstructions.
Parasitic Oscillations. Oscillations which occur at other than a desired frequency or its harmonics, or outside a tank circuit.
Precipitation Static. Radio interference experienced when the flight path is through precipitation.
Radiation. The phenomenon of electromagnetic waves spreading out in space from a source according to the laws of wave propagation.
Radio Interference. Any electrical disturbance which causes an undesirable response or malfunctioning in any electronic equipment.
Random Noise. An electrical disturbance that is completely without regularity in its detailed properties.
Receiver. Any electronic equipment in which unwanted signals may cause an undesirable response.
Shield. A partition between two regions of space such that electric and magnetic fields of interest are attenuated in passing from one region to the other.
Shot Effect. The irregularity of plate current in a vacuum tube due to variations in cathode emission.
Skin Effect. The crowding of current toward the surface, or skin, of a conductor.
Spurious Response. To minimize cross modulation and overloading, good engineering practice requires that one or more tuned circuits shall be placed ahead of the first RF amplifier stage of an interference meter. The meter should also be capable or rejecting spurious responses resulting from combinations with the fundamental or harmonics of the conversion oscillator system of the super-heterodyne section of the meter. The degree of rejection is measured in terms of attenuation in db relative to the desired signals. This spurious response rejection should be at least 40 db.
Surface Contact Transients. Transients resulting from the variation in contact resistance across sliding surfaces of rotating electrical machines.
Surface Transfer Impedance. The ratio of longitudinal voltage drop along the outside of a tubular shield to the current carried by the shield.
System. Contains two or more Sets or Major Units located at different positions but accomplishing their objective through interdependent or interrelated operations, as for example a Propeller Control System.
Thermal Agitation. The thermal motion of the conduction electrons in a resistor causing minute interfering currents.
To Bond. To connect between two points through a low impedance path.
Transmission Factor (referring to networks). The ratio of the voltage in the transmitted wave to that in the incident wave at a point of discontinuity.
Transmission Factor (referring to media). The ratio of the electric field intensity in the transmitted wave to that in the incident wave at a surface of discontinuity.
Transmit-Receive (TR) Box. A device used in radar sets to prevent the transmitted pulse from entering the receiver.
Undesirable Response. Any audible, visible, or otherwise measurable response of a receiver not produced by a desired signal provided that either its duration is longer than one second or its highest recurrence rate is during normal operation of the aircraft is greater than once every three minutes.
Wave Trap. A circuit designed to attenuate greatly one frequency or a very narrow band of frequencies while passing without appreciable attenuation all other frequencies. EMC
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