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September Fact-of-the-Day Index

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DateFact of the Day Topic
September 1Feed-Line Impedance The characteristic impedance of a feed-line is not a rational function of frequency (i.e., does not depend on frequency), because ...
September 2Frequency Scaling The performance of small-scale models of large antennas, cavity resonators, and other expensive components sometimes is ...
September 3Resonant Cavity Bandwidth The relative bandwidth of an RF cavity at resonance is approximately equal to the inner-surface-area times the effective skin-depth ...
September 4Electron Trajectory If an electron that has an initial velocity is injected ...
September 5Flat Ribbon Resistance A flat rectangular strip (ribbon) conductor has a lower RF to DC resistance ratio than a solid round wire of the same cross-section if ...
September 6Skin Effect Nearly all the current carried by a solid conductor is concentrated very near its surface at frequencies sufficiently high that ...
September 7Litz Wire The RF to DC resistance ratio of a conductor can be made to very closely approach unity at low radio frequencies by ...
September 8Resistor Inductance and Capacitance Every resistor has both inductance and capacitance. Inductance exists because ...
September 9Parabolic Antenna Reflectors Some people may think parabolic reflector antennas are relatively new. However, in 1932 Ren Darbord explained ...
September 10Mutual Antenna Impedance If RF power is coupled into an antenna from a transmitter, the RF current that flows in the antenna will ...
September 11Harmonic Traps Antiresonant (parallel-tuned) circuits connected in series with an RF transmission line at current antinodes are very effective in ...
September 12Parasitic Oscillations Parasitic oscillations often occur at high frequencies in radio frequency amplifiers and most suggested remedies ...
September 13Signal-to-Distortion Ratio Intermodulation distortion is the principal type of distortion generated in SSB transmitters. Intermodulation distortion usually is ...
September 14Spacetime Wormholes Instead of electrical charges being material particle objects ...
September 15Isotropic Antenna An isotropic antenna is an antenna that radiates or receives equally well in all directions. Practical antennas ...
September 16Omnidirectional Antenna An omnidirectional antenna is an antenna that produces a constant field strength in azimuth, but ...
September 17Copper Wire Hardness Most people are familiar with soft and hard-drawn copper wire. However, there are more grades than ...
September 18Beverage Antennas Beverage antennas, one of the most effective types of LF directive receiving antennas, were invented by ...
September 19Multiband Antennas The frequency range over which an antenna can be used effectively depends on more than maintaining a satisfactory ...
September 20Tower Wind Loading Area exposed to wind is the greatest single contributor to tower wind load. Wind load is far less where ...
September 21Weather Bureau Speeds The U.S. Weather Bureau discovered in about 1898 that their anemometers were indicating wind speeds about 25% higher ...
September 22Falling Ice Ice tends to form on antennas and supporting towers under certain conditions of temperature and humidity. Ice falling ...
September 23Helical Antenna Patterns Helical antennas can be made to have maximum radiation either in axial directions (end-fire) or in directions ...
September 24Vertical Tower Member Load Vertical tower members should be designed to withstand combined compression and ...
September 25Copper-Clad Steel Wire Copper-clad steel wire is produced by cladding a rod of steel core material with a copper strip and then drawing ...
September 26Tower Guy Grounding The importance of tower grounding to lightning safety is well known, but many overlook the importance of ...
September 27Antenna Bandwidths Different bandwidths can be correctly specified for the same antenna, because ...
September 28Antenna Effective Height The effective height of an antenna is the height of the center of ...
September 29Buried Power Service Not only do buried power lines tend to radiate significantly less radio-frequency noise than ...
September 30Vertical Radiator Pattern The azimuth radiation pattern of an isolated vertical radiator is perfectly circular because ...

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