Thursday, August 17, 2006

inner dork: television and radio

I thought this weeks, '"inner dork" appropriate to this weeks, "just askin''

Did you know....
There isn't a channel 1 on TV's.
Want to know why?
Of course you do.

In the 1930's , virtually all radio was AM and it took up a very small part of the available radio spectrum. Most companies wanted to use the rest of the spectrum for FM.

David Sarnoff, president of RCA, had another plan. He wanted the FCC to allocate part of the spectrum to 12 television channels which would provide three networks to every part of the country.

The FCC wasn't quick to jump on this idea because each television station would eat up to 30 times as much spectrum as a single FM channel. The FCC chairman thought the spectrum should be for radio, which the majority of Americans enjoyed, rather than for television which only a few wealthy families had at this time.

Sarnoff tried to force the FCC's speedy approval by demonstrating television at the 1939 World's Fair, hoping it would see the value of allocating room for 12 television channels. Rather than win over the FCC, Sarnoff's brash act angered the chairman, who quickly assigned RCA's proposed television Channel 1 to FM radio.

Today channel 1 is devoted to FM mobil services such as two-way radios for taxis. The other channels were never renumbered, and the original 12 television channels are still numbered 2-13. There is still not a Channel 1.

Prior to 1920, radio was used mainly for maritime, military, and commercial uses. No one considered using it for entertainment.
In 1915, David Sarnoff propsed his idea for a 'radio music box' to his superiors at the Marconi Wireless Telegraph Company of America. They turned it down. In 1920 he presented the idea to the newly formed Radio Corporation of America (RCA), which agreed to provide the money. Ta dah! Commercial radio was born.

The first licensed radio station in the U.S. was KDKA in Pittsburgh, PA.

David Sarnoff joined with General Electric and Westinghouse to create the first national radio network, the National Broadcasting Company (NBC). It was the first company in the U.S. created soley to operate a network of radio stations.


TrappedInColorado said...

Did you know... that the FCC was created to regulate the wireless spectrums after the Titantic disaster. Why? Because the wireless morse code transmitters of the day were all over the place. Unregulated. As they were attempting to transmit the names of the survivors they kept getting interrupted by other wireless operators on the same frequency. It was a mess.

puerileuwaite said...

As a dunce, I had no idea that there is no Channel 1. Oh, the time I have wasted.

Party Girl said...

Okay, I can't do links on my blog from this computer, but here is an interesting article I just found. I was going to make Farnsworth next week's power of one. I still might, but I thought this article was appropriate to share today.

Party Girl said...

..and Trapped: No, I didn't know that. Makes sense though. Thanks, for sharing. I do love my trivia.

Party Girl said...

p: me too. Me too.

I remember there being a Channel 1 when I was in high school, but it was a news magazine type thing that we had to watch.

Jay said...

Outer Dork: AM and FM.

AM stands for amplitude modulation,

AM radio ranges from 535 to 1705kHz (kilohertz, or thousands of cycles per-second of electromagnetic energy). These are the numbers you see on your AM radio dial, and some stations seen to endless repeat when they promote themselves. Stations can theoretically be placed every 10kHz, along the AM band. This means that there are a total of 117 different channels available for AM radio stations.

If it all stopped there, things would be rather simple; but, unfortunately, a lot of other factors come into play.

First, you can't put stations on the same frequency that are too close together in a geographic area. They will interfere with each other. And within an area you can't have two stations close together in frequency (too close to each other on the radio dial). So these are the first things that limit the number of radio stations in an area.

The good news is that since the signals of stations tend to be limited in their range, you can use some of the frequencies many times — as long as the stations are far enough apart geographically. This is why the United States can have nearly 5,000 AM radio stations on only 117 different frequencies.

How far an AM station's signal travels depends on such things as the station's frequency (channel), the power of the transmitter in watts, the nature of the transmitting antenna, how conductive the soil is around the antenna (damp soil is good; sand and rocks aren't), and, a thing called ionospheric refraction. (The ionosphere is a layer of heavily charged ion molecules above the earth's atmosphere.) Ionospheric refraction is a very big issue, since AM radio waves can end up hundreds and even thousands of miles away, and in the process interfere with all other stations on the same frequency. That's why at sunset most AM radio stations in the U.S. have to:

* reduce power

* directionalize their signal (send it more in some directions than others), or

* go off the air (sign off until sunrise of the next day)

This may explain why your favorite AM radio station goes off the air at sunset, or becomes much harder to hear (because of reduced power).

FM (frequency modulated) radio and TV waves don't' act in the same way as AM radio waves.

For starters, they are on a higher frequency in the RF spectrum. (The name RF, for radio frequency, was obviously named for radio, but when TV came along they just stuck with the name).

The FM radio band goes from 88 to 108 MHz (megahertz, or millions of cycles per second). Again, you can see these numbers on your FM radio dial. FM stations must be 200kHz apart at these frequencies, which means that there's room for 200 FM stations on the FM band.

But, unlike AM radio stations, FM stations don't end up being assigned frequencies with nice round numbers like 820 or 1240. Thus, an FM station may be at 88.7 on the dial.

You may have noticed that FM stations don't reduce power or sign off the air at sunset. That's because ionospheric refraction doesn't appreciably affect FM or TV signals. For the most part, FM and TV signals are line-of-sight. Although this means that FM stations don't interfere with each other, this characteristic creates a couple of other problems.

First, these waves go in a straight line and don't bend around the earth as AM ground waves do. They quickly disappear into space — which may be fine if you are sitting on Mars trying to listen to your FM radio.

If not, then the farther away from the FM or TV station you are, the higher you have to have an antenna to receive the FM or TV signal. Note that the earth is round — I hope this doesn't come as a shock to anyone — and, therefore, these signals will literally leave the earth after 50 miles or so.

And, there's another problem. Since FM and TV signals are line-of-sight, they can be stopped or reflected by things like mountains and buildings. In the case of solid objects like buildings, reflections create ghost images in TV pictures and that "swishing sound" when you listen to FM radio while driving around tall structures.

Of course, the higher the FM or TV transmitter antennas are the greater area they will cover — which explains why these antennas are commonly very tall, or placed on the top of mountains. AM radio doesn't need that kind of advantage, since AM radio waves don't behave in the same way.

Note also from the drawing above that FM and TV signals tend to go through the ionosphere rather than being refracted form it. Again, this means that no matter what the station's power, it's signal will at some point leave the earth.

Party Girl said...

ah, I love dorking.