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Yes, that's exactly why, because the FCC said to do it that way. There are countless examples of "why is it this way" being answered "because that is what some

Yes, that's exactly why, because the FCC said to do it that way. There are countless examples of "why is it this way" being answered "because that is what some arbitrary person picked." My favorite example of this I remember reading in Andrew Tanenbaum's Networking book that the first frequency-hopping protocols used 88 frequencies because that is how many keys there are on a piano: https://en.wikipedia.org/wiki/Frequency-hopping_spread_spectrum#Multiple_inventors https://en.wikipedia.org/wiki/Frequency-hopping_spread_spect...

kkjkok 13y ago
The most interesting part of that is the WHO of spread spectrum... Hedy Lamarr (movie star) and George Antheil (composer). Very fascinating that two major Hollywood players were able to innovate in hard science/math. A different era. I think the piano keys stuff was because the idea was semi-based around a player's piano (if I recall the legend from my DSP prof). The roll moves around and different bumps make the notes sound - a similar concept (visually at least) to coding a communications signal and having it jump all over frequency. 88 notes -> 88 frequencies. I wouldn't be surprised if the experimental equipment was a modified version of a player's piano. Very cool stuff, though I may be recollecting the story wrong. Wikipedia agrees about the movie star + composer bit at least.
baddox 13y ago
Article with headlines like "Why X was chosen" are expected to actually provide explanations of human motivation, rather than the nearest proximate cause. For example, an article called "Why this stretch of highway has a speed limit of 30 mph" would be expected to say something like "because there is a history of accidents there due to the narrow shoulder and tight turns" rather than "because the transportation department, which is in charge of setting speed limits, posted 30 mph signs there."
bnegreve 13y ago
> [Why] the first frequency-hopping protocols used 88 frequencies because that is how many keys there are on a piano Well, it is a rather arbitrary reason but a valid explanation. In the case of FM frequencies, the question remains ... why did they picked odd frequencies?
- coin 13y ago
  The frequency is the center of a 200kHz channel. The first channel is 88.0 - 88.2 MHz, thus the center is 88.1.
- TallGuyShort 13y ago
  As they say, "The center frequency is located at 1/2 the bandwidth of the FM Channel, or 100 kHz (0.1 MHz) up from the lower end of the channel." It's natural to pick a range between round numbers. so 88.0 MHz - 108.0 MHz doesn't seem so strange a range to be allocated. Now if one band starts at 88.0 MHz and needs 200 kHz of bandwidth, it's going to go from 88.0 MHz to 88.2 MHz. The carrier frequency will be in the middle of this band, so it's represented as 88.1 MHz.
- qbrass 13y ago
  >Well, it is a rather arbitrary reason but a valid explanation. It's not exactly arbitrary, it was inspired by a player piano, and the original patent used piano rolls. Using all of the keys just makes sense in that context.
ds9 13y ago
Another example is the Fahrenheit scale. The eponymous originator calibrated his thermometer by the temperatures where he could obtain brine (0 F) and an inaccurate estimate of human body temperature (100 F). https://en.wikipedia.org/wiki/Fahrenheit https://en.wikipedia.org/wiki/Fahrenheit
- amalag 13y ago
  It is still nice because it is human centric, roughly 0 to 100 for temperatures is easily relatable to the human body. 90 is hot, 10 is cold. Celsius starting at the freezing point of water is not as human centric.
  - raverbashing 13y ago
    No, it's still a piece of crap "Human centric" is a false advantage. And it's not even human centric, the temperature of 100F is wrong, and what does brine have to do again with the human body?
    - fancyketchup 13y ago
      Gah. Can we please stop with this bullshit already? Fahrenheit has nothing to do with body temperature. The human body temperature is ~100F by coincidence, not by design. The Fahrenheit scale has 180 divisions (nice round number, evenly divisible by loads of integers) between the freezing point of water and the boiling point of water (212F-32F=180, for the math challenged). The 0F point is the equilibrium point of a frigorific mixture of equal parts ammonium chloride, ice, and water. One can easily produce two reference points for the F scale in a way that isn't sensitive to the local pressure using just ice brine (0F) and ice water (32F). The melting temperature of ice and the equilibrium temperature of the brine mixture are constant on the pressure scales and temperature scales available to metrologists before about the 19th century[1][2]. The same can't be said for the Celsius scale, which requires either a triple-point cell or a known atmospheric pressure (so that the boiling temperature of water is well-known). Edit: So the close out the point, the Fahrenheit is a unit which is much better matched for the calibration tools and computational methods available around the time it was invented. [1] Maybe a better way to state this sentence is that the temperatures are constant "to within the experimental uncertainty achievable at the time." [2] It's well known to anyone who has ever cooked that water boils at an appreciably different temperature in Denver than in Los Angeles.

kkjkok 13y ago

The most interesting part of that is the WHO of spread spectrum... Hedy Lamarr (movie star) and George Antheil (composer). Very fascinating that two major Hollywood players were able to innovate in hard science/math. A different era. I think the piano keys stuff was because the idea was semi-based around a player's piano (if I recall the legend from my DSP prof). The roll moves around and different bumps make the notes sound - a similar concept (visually at least) to coding a communications signal and having it jump all over frequency. 88 notes -> 88 frequencies. I wouldn't be surprised if the experimental equipment was a modified version of a player's piano. Very cool stuff, though I may be recollecting the story wrong. Wikipedia agrees about the movie star + composer bit at least.

baddox 13y ago

Article with headlines like "Why X was chosen" are expected to actually provide explanations of human motivation, rather than the nearest proximate cause. For example, an article called "Why this stretch of highway has a speed limit of 30 mph" would be expected to say something like "because there is a history of accidents there due to the narrow shoulder and tight turns" rather than "because the transportation department, which is in charge of setting speed limits, posted 30 mph signs there."

bnegreve 13y ago

> [Why] the first frequency-hopping protocols used 88 frequencies because that is how many keys there are on a piano Well, it is a rather arbitrary reason but a valid explanation. In the case of FM frequencies, the question remains ... why did they picked odd frequencies?

coin 13y ago
The frequency is the center of a 200kHz channel. The first channel is 88.0 - 88.2 MHz, thus the center is 88.1.
TallGuyShort 13y ago
As they say, "The center frequency is located at 1/2 the bandwidth of the FM Channel, or 100 kHz (0.1 MHz) up from the lower end of the channel." It's natural to pick a range between round numbers. so 88.0 MHz - 108.0 MHz doesn't seem so strange a range to be allocated. Now if one band starts at 88.0 MHz and needs 200 kHz of bandwidth, it's going to go from 88.0 MHz to 88.2 MHz. The carrier frequency will be in the middle of this band, so it's represented as 88.1 MHz.
qbrass 13y ago
>Well, it is a rather arbitrary reason but a valid explanation. It's not exactly arbitrary, it was inspired by a player piano, and the original patent used piano rolls. Using all of the keys just makes sense in that context.

ds9 13y ago

Another example is the Fahrenheit scale. The eponymous originator calibrated his thermometer by the temperatures where he could obtain brine (0 F) and an inaccurate estimate of human body temperature (100 F). https://en.wikipedia.org/wiki/Fahrenheit https://en.wikipedia.org/wiki/Fahrenheit

amalag 13y ago
It is still nice because it is human centric, roughly 0 to 100 for temperatures is easily relatable to the human body. 90 is hot, 10 is cold. Celsius starting at the freezing point of water is not as human centric.
- raverbashing 13y ago
  No, it's still a piece of crap "Human centric" is a false advantage. And it's not even human centric, the temperature of 100F is wrong, and what does brine have to do again with the human body?
  - fancyketchup 13y ago
    Gah. Can we please stop with this bullshit already? Fahrenheit has nothing to do with body temperature. The human body temperature is ~100F by coincidence, not by design. The Fahrenheit scale has 180 divisions (nice round number, evenly divisible by loads of integers) between the freezing point of water and the boiling point of water (212F-32F=180, for the math challenged). The 0F point is the equilibrium point of a frigorific mixture of equal parts ammonium chloride, ice, and water. One can easily produce two reference points for the F scale in a way that isn't sensitive to the local pressure using just ice brine (0F) and ice water (32F). The melting temperature of ice and the equilibrium temperature of the brine mixture are constant on the pressure scales and temperature scales available to metrologists before about the 19th century[1][2]. The same can't be said for the Celsius scale, which requires either a triple-point cell or a known atmospheric pressure (so that the boiling temperature of water is well-known). Edit: So the close out the point, the Fahrenheit is a unit which is much better matched for the calibration tools and computational methods available around the time it was invented. [1] Maybe a better way to state this sentence is that the temperatures are constant "to within the experimental uncertainty achievable at the time." [2] It's well known to anyone who has ever cooked that water boils at an appreciably different temperature in Denver than in Los Angeles.