Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element. This second connection is done with an adjustable rod parallel to the radiating element. T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element. A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element. This second connection is done with an adjustable rod parallel to the radiating element. T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element. A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element. This second connection is done with an adjustable rod parallel to the radiating element. T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element. A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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An electrical quarter wavelength can be computed in metres as one fourth of 300 divided by frequency in megahertz. The physical length equals the electrical length times the Velocity Factor. In this example, 300 divided by 14.1 divided by 4 times 0.66 = 3.51 metre.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element. This second connection is done with an adjustable rod parallel to the radiating element. T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element. A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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An electrical quarter wavelength can be computed in metres as one fourth of 300 divided by frequency in megahertz. The physical length equals the electrical length times the Velocity Factor. In this example, 300 divided by 15 divided by 4 times 0.80 = 4 metres.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element. This second connection is done with an adjustable rod parallel to the radiating element. T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element. A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element. This second connection is done with an adjustable rod parallel to the radiating element. T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element. A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element. This second connection is done with an adjustable rod parallel to the radiating element. T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element. A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element. This second connection is done with an adjustable rod parallel to the radiating element. T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element. A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element. This second connection is done with an adjustable rod parallel to the radiating element. T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element. A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current. Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current. Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current. Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current. Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current. Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current. Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current. Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current. Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current. Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current. Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current. Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The polarization of an electromagnetic radio wave corresponds to the position of the electrical field with respect to the surface of the Earth: horizontal when the E field is parallel to ground and vertical when perpendicular to ground. The magnetic field is at 90 degrees (perpendicular) to the electrical field. Dipoles and Yagis are linearly polarized antennas (i.e., the electrical field has a constant orientation). Circular polarization, where the polarization rotates, can be obtained from helical beam antennas or with crossed linear antennas fed with the correct phase difference. "Sense" refers to the direction of the rotation: clockwise polarization for a receding wave is termed right-hand.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Crossed dipoles fed 90 degrees out of phase are the active elements of a turnstile antenna and produce circular polarization. The turnstile antenna is used for satellite communications.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Key word: NOT. Antennas featuring a fine wire wound around a shaft (e.g., HF mobile antennas) are "loaded helical-wound antennas"; these produce a linear polarization, i.e., vertical or horizontal depending on their positions relative to ground. The axial-mode helical antenna, with its corkscrew look, is used in satellite work and produces circular polarization.
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"Doppler shift: the change in frequency of a received signal due to the motion of the satellite. This requires adjustment of the transmit or receive frequency, with the common practice being to change the higher of the two frequencies in use" (http://www.amsat.org/). Low Earth orbiting satellites travel at speeds around 28 000 km/h. The higher the operating frequency, the higher the possible shift: for example, +/- 600 Hz on 10 m, +/- 3 kHz on 2 m and +/- 9 kHz on 70 cm.
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"A loss in signal strength of 20 dB or more can be expected with cross-polarization so it is important to use antennas with the same polarization as the stations with which you expect to communicate." (ARRL Antenna Book, 22nd ed., section 21.10.5 Polarization)
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Key word: NOT. Front feed (also known as focal feed or axial feed): circular reflector, the feed is centered in front of the reflector, very common on larger dish antennas. Offset feed (also known as off-axis): elliptical reflector, the feed is off to one side, out of the path of the radio waves, typical of domestic satellite receiving antennas. Cassegrain (based on the Cassegrain telescope): the feed is behind the dish and relies on a small convex secondary reflector in front of the dish. Newtonian: a bogus answer, valid for telescopes.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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A parabolic reflector dish provides significant gain because energy striking any point of the parabola is reflected to the focal point with the correct phase. On transmit, the inverse process takes place: all energy directed at the parabola from the feed antenna is reflected forward with the correct phase. High gain antennas used on UHF or microwave frequencies present a real risk to living tissues: never stand in front of a transmitting antenna.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The helical beam antenna is circularly polarized. Although it will respond to horizontally or vertically polarized waves, the full gain of the antenna can only be realized with a circularly polarized wave of the same "sense".
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The dipole, ground-plane and quad are all linearly polarized and thus respond optimally to waves polarized in a single given direction, horizontal or vertical as the case may be. Unless proper alignment is assured, a significant loss is incurred. The helical beam antenna is circularly polarized, it can deal with the rotating fields of a wave with circular polarization. Consequently, it can deal with any single polarization at any given angle.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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"Surface errors should not exceed 1/8 lambda in amateur operation. At 430 MHz, 1/8 lambda is 3.4 inches [8.6 cm], but at 10 GHz, it is 0.1476 inch [3.7 mm]! (...) Mesh can be used for the reflector surface to reduce weight and wind loading, but hole size should be less than 1/12 lambda." (ARRL Antenna Book 22nd ed., sect. 15.6.2)
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain. In this example, minus 3 dB plus 6 dB yields a net increase of 3 dB or twice the power.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Voltage peaks on the standing wave increase losses through the dielectric ( P = E squared divided by R ), current peaks on the standing wave increase conductor losses ( P = I squared times R ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain. In this example, minus 5 watts plus 3 dB yields a net increase of 3 dB or twice the remaining power of 195 watts.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain. In this example, minus 3 dB plus 9 dB yields a net increase of 6 dB or four times the power.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain. In this example, minus 1.5 dB plus 4.5 dB yields a net increase of 3 dB or twice the power.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain. In this example, a net gain of 3 dB yields twice the power.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain. In this example, minus 1 dB plus 10 dB yields a net increase of 9 dB or eight times the power.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain. In this example, an added 6 dB yields four times the power.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain. In this example, minus 1 dB plus 10 dB yields a net increase of 9 dB or eight times the power.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain. In this example, minus 1 dB plus 10 dB yields a net increase of 9 dB or eight times the power.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Greater antenna heights tend to lower the main radiation lobe where ground reflections end up in phase with direct radiation from the antenna.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Below one half-wavelength in antenna height, there is little point in selecting a given broadside direction: for example, choosing a north-south orientation to favour east-west radiation will not pay significant dividends for antennas close to ground.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Current penetration around an antenna depends first on frequency and then on soil conductivity and dielectric constant. At HF frequencies over salt water, penetration ranges from 5 to 18 centimetres. Over poor ground, penetration can exceed 10 metres.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Key words: DIPOLE AT A QUARTER WAVELENGTH HEIGHT. At heights below three eights of a wavelength, ground reflections cause horizontal dipoles to direct more energy straight up. At a height of one half-wavelength, radiation at 90 degrees is minimized and two lobes form at 30 degrees. In this comparison, the ground-mounted vertical undoubtedly exhibits a lower radiation angle as it cannot possibly radiate upwards.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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At heights below three eights of a wavelength, ground reflections cause horizontal dipoles to direct more energy straight up. At a height of one half-wavelength, radiation at 90 degrees is minimized and two lobes form at 30 degrees.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Below one half-wavelength in antenna height, there is little point in selecting a given broadside direction: for example, choosing a north-south orientation to favour east-west radiation will not pay significant dividends for antennas close to ground.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Depending on band (for example, 10, 15 and 20 metre) and distance, preferred radiation angles range from 1 to 25 degrees for long distance communication. A low radiation angle permits hitting the ionosphere at a greater distance for longer skip distances.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Depending on band (for example, 10, 15 and 20 metre) and distance, preferred radiation angles range from 1 to 25 degrees for long distance communication. A low radiation angle permits hitting the ionosphere at a greater distance for longer skip distances.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The impedance of a dipole in free space is known as 73 ohms. Below a height of a half-wavelength, impedance is greatly affected by ground proximity. At one wavelength and up, impedance begins to track the free-space value more closely.
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Near-Vertical Incidence Sky wave (NVIS) -- "The use of very low dipole antennas that radiate at very high elevation angles has become popular in emergency communications ("emcomm") systems. This works at low frequencies (7 MHz and below) that are lower than the ionosphere's critical frequency -- the highest frequency for which a signal traveling vertically will be reflected." (ARRL Handbook, 2012 ed., 21.2.12 NVIS Antennas)
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Near-Vertical Incidence Sky wave (NVIS) -- "The use of very low dipole antennas that radiate at very high elevation angles has become popular in emergency communications ("emcomm") systems. This works at low frequencies (7 MHz and below) that are lower than the ionosphere's critical frequency -- the highest frequency for which a signal traveling vertically will be reflected." (ARRL Handbook, 2012 ed., 21.2.12 NVIS Antennas)
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The power delivered to an antenna can be transformed in two ways: some of it is lost through heat and dielectric losses, the rest is radiated. The part that is radiated can be imagined to have "disappeared" into a virtual resistance. Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated. The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance. Except for electrically short antennas, radiation resistance makes up most of the antenna impedance. Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The power delivered to an antenna can be transformed in two ways: some of it is lost through heat and dielectric losses, the rest is radiated. The part that is radiated can be imagined to have "disappeared" into a virtual resistance. Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated. The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance. Except for electrically short antennas, radiation resistance makes up most of the antenna impedance. Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The power delivered to an antenna can be transformed in two ways: some of it is lost through heat and dielectric losses, the rest is radiated. The part that is radiated can be imagined to have "disappeared" into a virtual resistance. Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated. The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance. Except for electrically short antennas, radiation resistance makes up most of the antenna impedance. Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The power delivered to an antenna can be transformed in two ways: some of it is lost through heat and dielectric losses, the rest is radiated. The part that is radiated can be imagined to have "disappeared" into a virtual resistance. Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated. The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance. Except for electrically short antennas, radiation resistance makes up most of the antenna impedance. Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The power delivered to an antenna can be transformed in two ways: some of it is lost through heat and dielectric losses, the rest is radiated. The part that is radiated can be imagined to have "disappeared" into a virtual resistance. Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated. The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance. Except for electrically short antennas, radiation resistance makes up most of the antenna impedance. Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Beamwidth is defined as the width in degrees over which the major lobe is within 3 dB of maximum gain, this is equally described as the angle between the half-power points.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The power delivered to an antenna can be transformed in two ways: some of it is lost through heat and dielectric losses, the rest is radiated. The part that is radiated can be imagined to have "disappeared" into a virtual resistance. Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated. The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance. Except for electrically short antennas, radiation resistance makes up most of the antenna impedance. Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The power delivered to an antenna can be transformed in two ways: some of it is lost through heat and dielectric losses, the rest is radiated. The part that is radiated can be imagined to have "disappeared" into a virtual resistance. Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated. The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance. Except for electrically short antennas, radiation resistance makes up most of the antenna impedance. Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Beamwidth is defined as the width in degrees over which the major lobe is within 3 dB of maximum gain, this is equally described as the angle between the half-power points.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100. In this example, 72 divided by 74 is 97.3%
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100. In this example, 50 divided by 52 is 96.2%
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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