nc33/MultiSpan_SQUAD huggingface dataset:
Antenna_(radio)

The majority of antenna designs are based on the resonance principle. This relies on the behaviour of moving electrons, which reflect off surfaces where the dielectric constant changes, in a fashion similar to the way light reflects when optical properties change. In these designs, the reflective surface is created by the end of a conductor, normally a thin metal wire or rod, which in the simplest case has a feed point at one end where it is connected to a transmission line. The conductor, or element, is aligned with the electrical field of the desired signal, normally meaning it is perpendicular to the line from the antenna to the source (or receiver in the case of a broadcast antenna).

Question: What particle's migration does the resonance principle rely on?
Answer: electrons

Question: What is the basis for the way most antennas are developed?
Answer: resonance principle

Question: What type of surface is formed by the tip of a conductor?
Answer: reflective

Question: How would you place the conductor in relation to the signal you wished to obtain?
Answer: perpendicular
Antenna_(radio)

The ordinary half-wave dipole is probably the most widely used antenna design. This consists of two 1⁄4-wavelength elements arranged end-to-end, and lying along essentially the same axis (or collinear), each feeding one side of a two-conductor transmission wire. The physical arrangement of the two elements places them 180 degrees out of phase, which means that at any given instant one of the elements is driving current into the transmission line while the other is pulling it out. The monopole antenna is essentially one half of the half-wave dipole, a single 1⁄4-wavelength element with the other side connected to ground or an equivalent ground plane (or counterpoise). Monopoles, which are one-half the size of a dipole, are common for long-wavelength radio signals where a dipole would be impractically large. Another common design is the folded dipole, which is essentially two dipoles placed side-by-side and connected at their ends to make a single one-wavelength antenna.

Question: What is the most popular antenna type?
Answer: half-wave dipole

Question: What is the current usually beng put into it or pulled out of?
Answer: transmission line

Question: Elements in a half wave dipole and on an identical axis are said to be what?
Answer: collinear

Question: What antenna type is a portion of the half wave dipole?
Answer: Monopoles

Question: What popular type combines more that one antenna?
Answer: folded dipole
Antenna_(radio)

It is possible to use the impedance matching concepts to construct vertical antennas substantially shorter than the 1⁄4 wavelength at which the antenna is resonant. By adding an inductance in series with the antenna, a so-called loading coil, the capacitive reactance of this antenna can be cancelled leaving a pure resistance which can then be matched to the transmission line. Sometimes the resulting resonant frequency of such a system (antenna plus matching network) is described using the construct of electrical length and the use of a shorter antenna at a lower frequency than its resonant frequency is termed electrical lengthening.

Question: For use with more than one channel changes are made to increase what property?
Answer: impedance matching

Question: What could be coupled with an antenna to form pure resistance?
Answer: inductance

Question: What element would this pure resistance be coupled with?
Answer: transmission line

Question: What phrase describes the process of purposely using a lower standing antenna at a less than peak frequency?
Answer: electrical lengthening
Antenna_(radio)

Another extreme case of impedance matching occurs when using a small loop antenna (usually, but not always, for receiving) at a relatively low frequency where it appears almost as a pure inductor. Resonating such an inductor with a capacitor at the frequency of operation not only cancels the reactance but greatly magnifies the very small radiation resistance of such a loop.[citation needed] This is implemented in most AM broadcast receivers, with a small ferrite loop antenna resonated by a capacitor which is varied along with the receiver tuning in order to maintain resonance over the AM broadcast band

Question: What magnifies the small radiation resistance of a loop?
Answer: a capacitor at the frequency of operation

Question: What is resonated by a capacitor along with the receiver tuning that maintains resonance over the AM broadcast band?
Answer: small ferrite loop antenna

Question: What is used in most AM broadcaster receivers?
Answer: loop

Question: When using a small loop antenna at a low frequency, what may occur?
Answer: impedance matching
Antenna_(radio)

Antenna tuning generally refers to cancellation of any reactance seen at the antenna terminals, leaving only a resistive impedance which might or might not be exactly the desired impedance (that of the transmission line). Although an antenna may be designed to have a purely resistive feedpoint impedance (such as a dipole 97% of a half wavelength long) this might not be exactly true at the frequency that it is eventually used at. In some cases the physical length of the antenna can be "trimmed" to obtain a pure resistance. On the other hand, the addition of a series inductance or parallel capacitance can be used to cancel a residual capacitative or inductive reactance, respectively.

Question: What is left after antenna tuning?
Answer: resistive impedance

Question: Where does cancellation of any reactance seen?
Answer: antenna terminals

Question: What can be used to cancel a inductibe reactance or residual capacitative?
Answer: parallel capacitance

Question: What is an antenna designed to have?
Answer: purely resistive feedpoint
Antenna_(radio)

Rather than just using a thick tube, there are similar techniques used to the same effect such as replacing thin wire elements with cages to simulate a thicker element. This widens the bandwidth of the resonance. On the other hand, amateur radio antennas need to operate over several bands which are widely separated from each other. This can often be accomplished simply by connecting resonant elements for the different bands in parallel. Most of the transmitter's power will flow into the resonant element while the others present a high (reactive) impedance and draw little current from the same voltage. A popular solution uses so-called traps consisting of parallel resonant circuits which are strategically placed in breaks along each antenna element. When used at one particular frequency band the trap presents a very high impedance (parallel resonance) effectively truncating the element at that length, making it a proper resonant antenna. At a lower frequency the trap allows the full length of the element to be employed, albeit with a shifted resonant frequency due to the inclusion of the trap's net reactance at that lower frequency.

Question: What effect do cages have on the spectrum of usable frequencies?
Answer: widens

Question: What type of tubes are generally used for sturdier always of antennas?
Answer: cages

Question: How could one achieve the task of creating an antenna that can be Used over various bands?
Answer: connecting resonant elements

Question: What is an essential for dealing with directing the flow of power?
Answer: trap's
Antenna_(radio)

High-gain antennas have the advantage of longer range and better signal quality, but must be aimed carefully at the other antenna. An example of a high-gain antenna is a parabolic dish such as a satellite television antenna. Low-gain antennas have shorter range, but the orientation of the antenna is relatively unimportant. An example of a low-gain antenna is the whip antenna found on portable radios and cordless phones. Antenna gain should not be confused with amplifier gain, a separate parameter measuring the increase in signal power due to an amplifying device.

Question: Antennas with higher gain have what positive feature?
Answer: longer range

Question: What is a measure of how much efficient is improved by adding a device designed to make something stronger?
Answer: amplifier gain

Question: Dish network Tv takes example of what type of antenna?
Answer: parabolic dish

Question: What type of antenna would be best if placement was tricky?
Answer: Low-gain
Antenna_(radio)

Due to reciprocity (discussed above) the gain of an antenna used for transmitting must be proportional to its effective area when used for receiving. Consider an antenna with no loss, that is, one whose electrical efficiency is 100%. It can be shown that its effective area averaged over all directions must be equal to λ2/4π, the wavelength squared divided by 4π. Gain is defined such that the average gain over all directions for an antenna with 100% electrical efficiency is equal to 1. Therefore, the effective area Aeff in terms of the gain G in a given direction is given by:

Question: What must the relationship of an antenna and the receiving area be due to reciprocity?
Answer: proportional

Question: what could an antenna with complete electrical efficiency be said to have?
Answer: no loss

Question: Another term for the effective area is?
Answer: Aeff

Question: hat could an antenna with complete electrical efficiency be said to have?
Answer: 1
Antenna_(radio)

Efficiency of a transmitting antenna is the ratio of power actually radiated (in all directions) to the power absorbed by the antenna terminals. The power supplied to the antenna terminals which is not radiated is converted into heat. This is usually through loss resistance in the antenna's conductors, but can also be due to dielectric or magnetic core losses in antennas (or antenna systems) using such components. Such loss effectively robs power from the transmitter, requiring a stronger transmitter in order to transmit a signal of a given strength.

Question: A measure of the power that is useable and the power absorbed by the terminals?
Answer: Efficiency

Question: What happens to the power that is not absorbed by the antenna?
Answer: heat

Question: What can cause that reaction?
Answer: magnetic core losses

Question: What can cause that reaction?
Answer: transmitter
Antenna_(radio)

For instance, if a transmitter delivers 100 W into an antenna having an efficiency of 80%, then the antenna will radiate 80 W as radio waves and produce 20 W of heat. In order to radiate 100 W of power, one would need to use a transmitter capable of supplying 125 W to the antenna. Note that antenna efficiency is a separate issue from impedance matching, which may also reduce the amount of power radiated using a given transmitter. If an SWR meter reads 150 W of incident power and 50 W of reflected power, that means that 100 W have actually been absorbed by the antenna (ignoring transmission line losses). How much of that power has actually been radiated cannot be directly determined through electrical measurements at (or before) the antenna terminals, but would require (for instance) careful measurement of field strength. Fortunately the loss resistance of antenna conductors such as aluminum rods can be calculated and the efficiency of an antenna using such materials predicted.

Question: What would need to be placed into the transmitter to create ten W oh warmth? 
Answer: 100 W

Question: What would need to be investigated to determine how much power was radiated?
Answer: electrical measurements

Question: What factor may play a hand in lessened power from a transmitter?
Answer: impedance matching
Antenna_(radio)

According to reciprocity, the efficiency of an antenna used as a receiving antenna is identical to the efficiency as defined above. The power that an antenna will deliver to a receiver (with a proper impedance match) is reduced by the same amount. In some receiving applications, the very inefficient antennas may have little impact on performance. At low frequencies, for example, atmospheric or man-made noise can mask antenna inefficiency. For example, CCIR Rep. 258-3 indicates man-made noise in a residential setting at 40 MHz is about 28 dB above the thermal noise floor. Consequently, an antenna with a 20 dB loss (due to inefficiency) would have little impact on system noise performance. The loss within the antenna will affect the intended signal and the noise/interference identically, leading to no reduction in signal to noise ratio (SNR).

Question: What is the median level for measuring atmospheric noise?
Answer: thermal noise floor

Question: In what type of programs would low efficiency antennas not make a difference in effectiveness?
Answer: receiving

Question: At lesser frequencies what can account for incorrect assumptions about efficiency?
Answer: man-made noise

Question: What is SNR?
Answer: signal to noise ratio
Antenna_(radio)

The polarization of an antenna refers to the orientation of the electric field (E-plane) of the radio wave with respect to the Earth's surface and is determined by the physical structure of the antenna and by its orientation; note that this designation is totally distinct from the antenna's directionality. Thus, a simple straight wire antenna will have one polarization when mounted vertically, and a different polarization when mounted horizontally. As a transverse wave, the magnetic field of a radio wave is at right angles to that of the electric field, but by convention, talk of an antenna's "polarization" is understood to refer to the direction of the electric field.

Question: How many polarizations will a antenna have when mounted vertically?
Answer: one

Question: What is another name for electric-field?
Answer: E-plane

Question: When is a magnetic fields right angles to a electrical field?
Answer: transverse wave

Question: Whats understood in reference of direction of an E-plane?
Answer: polarization
Antenna_(radio)

Polarization is predictable from an antenna's geometry, although in some cases it is not at all obvious (such as for the quad antenna). An antenna's linear polarization is generally along the direction (as viewed from the receiving location) of the antenna's currents when such a direction can be defined. For instance, a vertical whip antenna or Wi-Fi antenna vertically oriented will transmit and receive in the vertical polarization. Antennas with horizontal elements, such as most rooftop TV antennas in the United States, are horizontally polarized (broadcast TV in the U.S. usually uses horizontal polarization). Even when the antenna system has a vertical orientation, such as an array of horizontal dipole antennas, the polarization is in the horizontal direction corresponding to the current flow. The polarization of a commercial antenna is an essential specification.

Question: Whats predictable about an antenna's geometry?
Answer: Polarization

Question: The polarization of what antenna is essential specification?
Answer: commercial antenna

Question: Most rooftop antenna's are polarized in which direction?
Answer: horizontal

Question: What is a more complicated type of polarization from an antenna's geometry?
Answer: quad antenna
Antenna_(radio)

Maximum power transfer requires matching the impedance of an antenna system (as seen looking into the transmission line) to the complex conjugate of the impedance of the receiver or transmitter. In the case of a transmitter, however, the desired matching impedance might not correspond to the dynamic output impedance of the transmitter as analyzed as a source impedance but rather the design value (typically 50 ohms) required for efficient and safe operation of the transmitting circuitry. The intended impedance is normally resistive but a transmitter (and some receivers) may have additional adjustments to cancel a certain amount of reactance in order to "tweak" the match. When a transmission line is used in between the antenna and the transmitter (or receiver) one generally would like an antenna system whose impedance is resistive and near the characteristic impedance of that transmission line in order to minimize the standing wave ratio (SWR) and the increase in transmission line losses it entails, in addition to supplying a good match at the transmitter or receiver itself.

Question: What requires matching of the empedance to an antenna system?
Answer: Maximum power transfer

Question: Why would a transmitter have additional adjustments?
Answer: "tweak" the match

Question: What is SWR?
Answer: standing wave ratio

Question: What is the desired design value for transmmiting circuitry?
Answer: 50 ohms
Antenna_(radio)

So an additional problem beyond canceling the unwanted reactance is of matching the remaining resistive impedance to the characteristic impedance of the transmission line. In principle this can always be done with a transformer, however the turns ratio of a transformer is not adjustable. A general matching network with at least two adjustments can be made to correct both components of impedance. Matching networks using discrete inductors and capacitors will have losses associated with those components, and will have power restrictions when used for transmitting. Avoiding these difficulties, commercial antennas are generally designed with fixed matching elements or feeding strategies to get an approximate match to standard coax, such as 50 or 75 Ohms. Antennas based on the dipole (rather than vertical antennas) should include a balun in between the transmission line and antenna element, which may be integrated into any such matching network.

Question: What is not adjustable when it comes to a transformer?
Answer: turns ratio

Question: How many ohms are in are in a standard coax?
Answer: 50 or 75

Question: A general matching network needs a minimum of how many adjustments to correct all components of impedance?
Answer: two adjustments

Question: What is included between the transmission line and the antenna element?
Answer: balun

Question: A balun should be integrated into what?
Answer: matching network
Antenna_(radio)

Unlike the above antennas, traveling wave antennas are nonresonant so they have inherently broad bandwidth. They are typically wire antennas multiple wavelengths long, through which the voltage and current waves travel in one direction, instead of bouncing back and forth to form standing waves as in resonant antennas. They have linear polarization (except for the helical antenna). Unidirectional traveling wave antennas are terminated by a resistor at one end equal to the antenna's characteristic resistance, to absorb the waves from one direction. This makes them inefficient as transmitting antennas.

Question: What antenna's are nonresonant?
Answer: traveling wave antennas

Question: How long are the wire antenna's that the voltage and current waves travel in the same direction?
Answer: one direction

Question: What are undirectional traveling wave directions terminated by?
Answer: resistor

Question: What antenna does not have linear polarization?
Answer: helical antenna

Question: What is the resistor equal to?
Answer: antenna's characteristic resistance
Antenna_(radio)

The phase of reflection of electromagnetic waves depends on the polarization of the incident wave. Given the larger refractive index of the ground (typically n=2) compared to air (n=1), the phase of horizontally polarized radiation is reversed upon reflection (a phase shift of  radians or 180°). On the other hand, the vertical component of the wave's electric field is reflected at grazing angles of incidence approximately in phase. These phase shifts apply as well to a ground modelled as a good electrical conductor.

Question: What is the refractive index of the ground?
Answer: n=2

Question: When is polarized radiation reversed?
Answer: reflection

Question: What is the refractive index of air?
Answer: n=1

Question: Besides a ground, what has these phases apply well to?
Answer: electrical conductor
Antenna_(radio)

When an electromagnetic wave strikes a plane surface such as the ground, part of the wave is transmitted into the ground and part of it is reflected, according to the Fresnel coefficients. If the ground is a very good conductor then almost all of the wave is reflected (180° out of phase), whereas a ground modeled as a (lossy) dielectric can absorb a large amount of the wave's power. The power remaining in the reflected wave, and the phase shift upon reflection, strongly depend on the wave's angle of incidence and polarization. The dielectric constant and conductivity (or simply the complex dielectric constant) is dependent on the soil type and is a function of frequency.

Question: Who proposed this theory?
Answer: Fresnel coefficients

Question: Is the ground has a great conductor, how much of the wave will be reflected?
Answer: 180° out of phase

Question: what is reflected and transmitted into the ground when a plane surface is struck?
Answer: electromagnetic wave

Question: What depends on the polarization and waves angle?
Answer: power remaining
Antenna_(radio)

The effective area or effective aperture of a receiving antenna expresses the portion of the power of a passing electromagnetic wave which it delivers to its terminals, expressed in terms of an equivalent area. For instance, if a radio wave passing a given location has a flux of 1 pW / m2 (10−12 watts per square meter) and an antenna has an effective area of 12 m2, then the antenna would deliver 12 pW of RF power to the receiver (30 microvolts rms at 75 ohms). Since the receiving antenna is not equally sensitive to signals received from all directions, the effective area is a function of the direction to the source.

Question: What is the portion of something that is reached by the radio transmission called?
Answer: aperture

Question: What effects the function of signals received by an antenna?
Answer: direction

Question: What is a measure of the power of an antenna?
Answer: microvolts

Question: How much power will be delivered to the reciever if the antenna has an effective area of 12 m/2?
Answer: 12 pW of RF power
Flowering_plant

The flowering plants (angiosperms), also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants, with about 350,000 species. Like gymnosperms, angiosperms are seed-producing plants; they are distinguished from gymnosperms by characteristics including flowers, endosperm within the seeds, and the production of fruits that contain the seeds. Etymologically, angiosperm means a plant that produces seeds within an enclosure, in other words, a fruiting plant. The term "angiosperm" comes from the Greek composite word (angeion-, "case" or "casing", and sperma, "seed") meaning "enclosed seeds", after the enclosed condition of the seeds.

Question: What are the most diverse group of land plants?
Answer: angiosperms

Question: How many species of flowering plants are there about?
Answer: 350,000

Question: What does an angiosperm produce its seeds within?
Answer: an enclosure

Question: What do angiosperms have in common with gymnosperms?
Answer: seed-producing plants

Question: What is the Greek word for "case" or "casing"?
Answer: angeion