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Why Do FM Frequencies End in an Odd Decimal?

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Re: Why Do FM Frequencies End in an Odd Decimal?

#41

Post by kkjkok »

datawander wrote: post #4
blueblob wrote: post #2

Did I miss something, or did this not answer the question in it's heading? It basically says it's like this in the US.

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/Freq…

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.

Re: Why Do FM Frequencies End in an Odd Decimal?

#42

Post by aestra »

mayonnaise23 wrote: post #35

I imported a car from Japan and it would get audio from TV stations as the radio went down to lower frequencies =)

Before the North American conversion to a digital only TV broadcasts, the audio for all analog channel 6 television stations in the United States could be picked up on 87.7 FM

Some channel 6 stations have expressed interest in/have implemented also broadcasting the sound for their broadcasts back on radio again after moving solely to digital broadcasts.

http://en.wikipedia.org/wiki/87.7_FM

Re: Why Do FM Frequencies End in an Odd Decimal?

#43

Post by marcosdumay »

Pxtl wrote: post #23
raverbashing wrote: post #22

Earlier quoted context omitted.

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?

Yeah, you could argue that if it was an accurate 100F for the human body, but you'd still want the bottom level to be something useful - freezing point of water is as good a zero as anything (well, short of absolute zero). My bigger question is why Metric stuck with Celcius and Kelvin instead of factoring in the Gas Constant (R) into Kelvin so the math would be completely constant-free. Of course, then you'd have wat…

The Metric system changes are all about preserving the measures people are used to, and not at all about removing constants from calculations.

Re: Why Do FM Frequencies End in an Odd Decimal?

#44

Post by baddox »

datawander wrote: post #4
blueblob wrote: post #2

Did I miss something, or did this not answer the question in it's heading? It basically says it's like this in the US.

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/Freq…

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."

Re: Why Do FM Frequencies End in an Odd Decimal?

#45

Post by baddox »

eigenvector wrote: post #36
amalag wrote: post #20

Earlier quoted context omitted.

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.

Fahrenheit is not intuitive, you just think so because you grew up with it. People who grew up with Celcius have no problem relating to how cold 30 C or 100 C or -20 C are.

Celsius is no more intuitive for everyday usage. Of all the scientific unit debates, the temperature one is by far the silliest. There are very few temperatures that people need to memorize, and they're trivial to memorize in either temperature scale.

Re: Why Do FM Frequencies End in an Odd Decimal?

#46

Post by baddox »

bcj wrote: post #40
stephencanon wrote: post #24

Earlier quoted context omitted.

0 is uncomfortably cold. 100 is uncomfortably hot. The temperatures that non-STEM people (“humans”) deal with on a day-to-day basis can be represented with satisfactory precision using two digits (OK, three in Australia), no negative numbers, no decimals. It’s a great system for casual temperatures. Whereas “reasonable” temperatures in C run from what, -18ish to 38ish? Where’s the sense in that? If you want to defend…

There are a lot of humans that live places where we regularly see negative temperatures. Where I live the temperature range is roughly -40–85ºF. Choosing the freezing point of water isn't really mystic. It lets you know whether it will rain or snow. It also means that any negative temperature is capable of causing frostbite.

> Choosing the freezing point of water isn't really mystic. It lets you know whether it will rain or snow.

Fahrenheit also has a chosen freezing point of water: 32 degrees. This is no more difficult to remember than Celsius' zero degree freezing point.

Re: Why Do FM Frequencies End in an Odd Decimal?

#48

Post by fancyketchup »

raverbashing wrote: post #22
amalag wrote: post #20

Earlier quoted context omitted.

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.

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?

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.

Re: Why Do FM Frequencies End in an Odd Decimal?

#49

Post by coin »

bnegreve wrote: post #9
datawander wrote: post #4

Earlier quoted context omitted.

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/Freq…

> [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?

The frequency is the center of a 200kHz channel. The first channel is 88.0 - 88.2 MHz, thus the center is 88.1.

Re: Why Do FM Frequencies End in an Odd Decimal?

#50

Post by saraid216 »

stephencanon wrote: post #24
raverbashing wrote: post #22

Earlier quoted context omitted.

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?

0 is uncomfortably cold. 100 is uncomfortably hot. The temperatures that non-STEM people (“humans”) deal with on a day-to-day basis can be represented with satisfactory precision using two digits (OK, three in Australia), no negative numbers, no decimals. It’s a great system for casual temperatures. Whereas “reasonable” temperatures in C run from what, -18ish to 38ish? Where’s the sense in that? If you want to defend…

> (mysticism about the vitality of water is not a real justification)

Water was also used in the original definition of a gram, which is a fairly good reason to reuse it in another definition.

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