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