4 ms·

"One key point is that in neither case is any amplification or "gain" present." "Antenna gain relative to an isotropic radiator is a thing." Which is it? Gain

"One key point is that in neither case is any amplification or "gain" present." "Antenna gain relative to an isotropic radiator is a thing." Which is it? Gain clearly does not mean amplification always as I pointed to multiple references and you provided absolutely none. "There is no such term as electronics gain." Again: https://en.wikipedia.org/wiki/Gain_(electronics) https://en.wikipedia.org/wiki/Gain_(electronics) In electronics, gain is a measure of the ability of a two-port circuit (often an amplifier) to increase the power or amplitude of a signal from the input to the output port What game are you playing here, are you really just redefining the english language to win an internet argument?

entropicgravity 5y ago
At the transmitter there are two kinds of gain. The first is simply crack up the power and more signal energy will be received at the receiver. The other "gain" is where the physical shape of the transmitting antenna directs more of the energy it receives in one direction (usually straight ahead) rather than a different directions. The amount of gain due to the physical shape will vary with the frequency of radio wave relative to the physical shape the antenna. Think of a flashlight. The beam is brighter in the middle and falls off towards the sides. That's "gain" compared to a flashlight that beams light in all directions equally, like a sphere. So while the transmitter can "shape the beam" to create gain, the receiver cannot (though the path lose equation implies that it does). The receiver can physically just trap the amount of watts per square metre that it receives and this amount depends only on its size and not on the frequency of the incoming radiation. So the transmitter and receiver antennas are very different in their physics of how the operate but the Path Loss Equations fudges things to make it look like they are the same ie that the gain of either is equally dependent on the frequency/wave length when in fact that's false and the two antennas are asymmetric in how they respond the carrier frequency.
- SigmundA 5y ago
  So while the transmitter can "shape the beam" to create gain, the receiver cannot (though the path lose equation implies that it does). The receiver can physically just trap the amount of watts per square metre that it receives and this amount depends only on its size and not on the frequency of the incoming radiation. So radio telescopes don't shape the incoming radiation? You can't just have a big flat antenna with a lot of area, they use dish reflectors and wave guides to shape the incoming radiation down to the actual antenna that has a size determined by guess what, FREQUENCY. "Figure 3.3: Most high-frequency feeds are quarter-wave ground-plane verticals inside waveguide horns. The only true antenna in this figure is the λ/4 ground-plane vertical, which converts electromagnetic waves in the waveguide to currents in the coaxial cable extending down from the waveguide. According to the strict definition of an antenna as a device for converting between electromagnetic waves in space and currents in conductors, the only antennas in most radio telescopes are half-wave dipoles and their relatives, quarter-wave ground-plane verticals. The large parabolic reflector of a radio telescope serves only to focus plane waves onto the feed antenna. (The term “feed” comes from radar antennas used for transmitting; the “feed” antenna feeds transmitter power to the main reflector. Receiving antennas used in radio astronomy work the other way around, and the “feed” actually collects radiation from the reflector.) https://www.cv.nrao.edu/~sransom/web/Ch3.html https://www.cv.nrao.edu/~sransom/web/Ch3.html
  - entropicgravity 5y ago
    What ever it is you think might be happening at the receiver, if it violates conservation of energy it's unlikely to be correct.
    - SigmundA 5y ago
      Conservation of energy directly leads to the role of frequency in antenna reception and reciprocity: Figure 3.5: A cavity in thermodynamic equilibrium at temperature T containing a resistor R is coupled to an antenna, also at temperature T, through a filter blocking electromagnetic radiation but passing currents having frequencies in the range ν to ν+dν. Imagine an antenna inside a cavity in full thermodynamic equilibrium at temperature T connected through a transmission line to a matched resistor (whose resistance equals the radiation resistance of the antenna) in a second cavity at the same temperature (Figure 3.5). A filter between the cavities passes only currents in a narrow range of frequencies between ν and ν+dν. Because this entire system is in thermodynamic equilibrium, no net power can flow through the wires connecting the antenna and the resistor. Otherwise, one cavity would heat up and the other would cool down, in violation of the second law of thermodynamics.
CamperBob2 5y ago
The article casually equates gain to change in "power or amplitude of a signal." While not wrong per se, this is one of the drawbacks of using lay references in specific fields. Power and amplitude mean the same thing to 99% of people, but they are not the same thing at all. Amplitude is measured in volts, while power is measured in watts. Voltage doesn't do work, convey information, or obey conservation laws; power does. As a result, when engineers refer to gain in voltage alone, they will (or should) go out of their way to use the term "voltage gain." Otherwise it's a power ratio, in which the denominator is typically a given number of watts or the power present at the feedpoint of a hypothetical isotropic antenna. Antenna people rarely care about voltage gain outside the context of impedance matching or regulatory matters. Voltage is useful when discussing field strength in volts per meter, but at the end of the day, the antenna engineer's job is to deliver power, not voltage. (Also, to avoid embarrassing Steve Jobs.)
- SigmundA 5y ago
  You casually provide nothing contradictory to what I have stated and have multiple times dismissed power gain in antennas, electronic amplifiers have electronic gain, antennas have gain not dependent on electronic amplification, gain is the correct word. With antennas it is power gain not voltage gain, but gain non the less, thank you for confirming GAIN is the correct term in the most ridiculous concession possible...WTF.
  - CamperBob2 5y ago
    Sounds good, best of luck in your studies.

entropicgravity 5y ago

At the transmitter there are two kinds of gain. The first is simply crack up the power and more signal energy will be received at the receiver. The other "gain" is where the physical shape of the transmitting antenna directs more of the energy it receives in one direction (usually straight ahead) rather than a different directions. The amount of gain due to the physical shape will vary with the frequency of radio wave relative to the physical shape the antenna. Think of a flashlight. The beam is brighter in the middle and falls off towards the sides. That's "gain" compared to a flashlight that beams light in all directions equally, like a sphere. So while the transmitter can "shape the beam" to create gain, the receiver cannot (though the path lose equation implies that it does). The receiver can physically just trap the amount of watts per square metre that it receives and this amount depends only on its size and not on the frequency of the incoming radiation. So the transmitter and receiver antennas are very different in their physics of how the operate but the Path Loss Equations fudges things to make it look like they are the same ie that the gain of either is equally dependent on the frequency/wave length when in fact that's false and the two antennas are asymmetric in how they respond the carrier frequency.

SigmundA 5y ago
So while the transmitter can "shape the beam" to create gain, the receiver cannot (though the path lose equation implies that it does). The receiver can physically just trap the amount of watts per square metre that it receives and this amount depends only on its size and not on the frequency of the incoming radiation. So radio telescopes don't shape the incoming radiation? You can't just have a big flat antenna with a lot of area, they use dish reflectors and wave guides to shape the incoming radiation down to the actual antenna that has a size determined by guess what, FREQUENCY. "Figure 3.3: Most high-frequency feeds are quarter-wave ground-plane verticals inside waveguide horns. The only true antenna in this figure is the λ/4 ground-plane vertical, which converts electromagnetic waves in the waveguide to currents in the coaxial cable extending down from the waveguide. According to the strict definition of an antenna as a device for converting between electromagnetic waves in space and currents in conductors, the only antennas in most radio telescopes are half-wave dipoles and their relatives, quarter-wave ground-plane verticals. The large parabolic reflector of a radio telescope serves only to focus plane waves onto the feed antenna. (The term “feed” comes from radar antennas used for transmitting; the “feed” antenna feeds transmitter power to the main reflector. Receiving antennas used in radio astronomy work the other way around, and the “feed” actually collects radiation from the reflector.) https://www.cv.nrao.edu/~sransom/web/Ch3.html https://www.cv.nrao.edu/~sransom/web/Ch3.html
- entropicgravity 5y ago
  What ever it is you think might be happening at the receiver, if it violates conservation of energy it's unlikely to be correct.
  - SigmundA 5y ago
    Conservation of energy directly leads to the role of frequency in antenna reception and reciprocity: Figure 3.5: A cavity in thermodynamic equilibrium at temperature T containing a resistor R is coupled to an antenna, also at temperature T, through a filter blocking electromagnetic radiation but passing currents having frequencies in the range ν to ν+dν. Imagine an antenna inside a cavity in full thermodynamic equilibrium at temperature T connected through a transmission line to a matched resistor (whose resistance equals the radiation resistance of the antenna) in a second cavity at the same temperature (Figure 3.5). A filter between the cavities passes only currents in a narrow range of frequencies between ν and ν+dν. Because this entire system is in thermodynamic equilibrium, no net power can flow through the wires connecting the antenna and the resistor. Otherwise, one cavity would heat up and the other would cool down, in violation of the second law of thermodynamics.

CamperBob2 5y ago

The article casually equates gain to change in "power or amplitude of a signal." While not wrong per se, this is one of the drawbacks of using lay references in specific fields. Power and amplitude mean the same thing to 99% of people, but they are not the same thing at all. Amplitude is measured in volts, while power is measured in watts. Voltage doesn't do work, convey information, or obey conservation laws; power does. As a result, when engineers refer to gain in voltage alone, they will (or should) go out of their way to use the term "voltage gain." Otherwise it's a power ratio, in which the denominator is typically a given number of watts or the power present at the feedpoint of a hypothetical isotropic antenna. Antenna people rarely care about voltage gain outside the context of impedance matching or regulatory matters. Voltage is useful when discussing field strength in volts per meter, but at the end of the day, the antenna engineer's job is to deliver power, not voltage. (Also, to avoid embarrassing Steve Jobs.)

SigmundA 5y ago
You casually provide nothing contradictory to what I have stated and have multiple times dismissed power gain in antennas, electronic amplifiers have electronic gain, antennas have gain not dependent on electronic amplification, gain is the correct word. With antennas it is power gain not voltage gain, but gain non the less, thank you for confirming GAIN is the correct term in the most ridiculous concession possible...WTF.
- CamperBob2 5y ago
  Sounds good, best of luck in your studies.