Where “Wireless” Began!
On This Day: December 11, 1909 — Guillermo Marconi was awarded the Nobel Prize In Physics for his work and invention of wireless telegraph communication
“At my home near Bologna, in Italy, I commenced early in 1895 to carry out tests and experiments with the object of determining whether it would be possible by means of Hertzian waves to transmit to a distance telegraphic signs and symbols without the aid of connecting wires.
After a few preliminary experiments with Hertzian waves I became very soon convinced, that if these waves or similar waves could be reliably transmitted and received over considerable distances a new system of communication would become available possessing enormous advantages over flashlights and optical methods, which are so much dependent for their success on the clearness of the atmosphere.” — from the acceptance speech of Marconi on December 11, 1909
Facts & Information:
“Radio Waves” are electromagnetic waves.
“Like ocean waves, radio waves have a certain speed, length, and frequency. The speed is simply how fast the wave travels between two places. The wavelength is the distance between one crest (wave peak) and the next, while the frequency is the number of waves that arrive each second. Frequency is measured with a unit called hertz, so if seven waves arrive in a second, we call that seven hertz (7 Hz).” — explainthatstuff
Radio waves are invisible.
Radio waves are completely undetectable by human ears.
Radio waves are used by . . . .
- cell phones
- baby monitors
- radio stations
- emergency service radios
- garage door openers
- radio-controlled toys
- Ham radios
- satellite communications-GPS
- wireless computer networks
- bluetooth devices
- Short-wave radios
- wireless mics
- wireless powerpoint devices
- car key fobs
- wireless security systems
Radio waves surround us and are sending information at all different frequencies.
The frequencies of those radio waves run from VHF (Very High Frequencies) to Infrared (just before visible light).
“In the United States, the FCC (Federal Communications Commission) decides who is able to use which frequencies for which purposes, and it issues licenses to stations for specific frequencies.”
AM & FM stations involve “amplification” and “frequency” modulation. Modulation means change – a rapidly changing electrical current.
PM: Pulse Modulation — simply turn the current on and off, such as was used to send morse code over wires. PM can also be sent through the air.
AM = Amplitude Modulation: The music or voice combined with the steady stream of the frequency produces changes in the amplitude or strength of the wave (no change to the frequency) when it is an AM channel
FM = Frequency Modulation: The music or voice combined with the steady stream of the frequency produces changes of low and high to the frequency (no change to the amplitude) when it is an FM channel
“An example makes this clearer. Suppose I’m on a rowboat in the ocean pretending to be a radio transmitter and you’re on the shore pretending to be a radio receiver. Let’s say I want to send a distress signal to you. I could rock the boat up and down quickly in the water to send big waves to you. If there are already waves traveling past my boat, from the distant ocean to the shore, my movements are going to make those existing waves much bigger. In other words, I will be using the waves passing by as a carrier to send my signal and, because I’ll be changing the height of the waves, I’ll be transmitting my signal by amplitude modulation. Alternatively, instead of moving my boat up and down, I could put my hand in the water and move it quickly back and forth. Now I’ll make the waves travel more often—increasing their frequency. So, in this case, my signal will travel to you by frequency modulation.” — explainthatstuff
If you are listening to an AM radio station, broadcasting at 770, that means that the station is broadcasting at 770 kilohertz — or 770,000 cycles per second
If you are listening to an FM radio station, broadcasting at 91.5 Mhz that means that the station is broadcasting at a frequency of 91.5 megahertz — cycling at 91,500,000 cycles per second!
There are approximately 300 billion frequencies — modulating at Hertz, Kilohertz, and Megahertz.
A transmitter transmits at a set the frequency.
A receiver or “tuner” is tuned to receive the frequency.
“Tuners work using a principle called resonance. That is, tuners resonate at, and amplify, one particular frequency and ignore all the other frequencies in the air.”
An antenna is used to increase the range of the transmission and/or the ability to receive the transmitted frequency. An antenna can be a simple piece of wire to a 200-foot diameter satellite dish used to receive radio waves from space.
The radio stations across the US are licensed by the FCC, which controls the strength of a radio station’s signal and the distance between radio stations so that one station does not interfere with another station’s broadcast.
If a radio station’s transmitter is not properly calibrated or functioning, sometimes it will accidentally “steps-on” another frequency and interferes with that radio station’s broadcast.
The FCC controls radio transmission because there are a limited number of frequencies which can be broadcast without interfering with each other across the United States.
Frequencies east of the Mississippi River begin with the call letter “W,” and west of the Mississippi begin with the call letter “K.”
Other stations can and do broadcast on the same frequency if they are far enough apart geographically so as not to interfere with that other station — for instance, there are 207 stations in the US broadcast at 89.3 FM
There are “pirate stations” which broadcast unlicensed AM and FM signals in violation of the FCC regulators. Some of these stations operate outside of the territorial waters of a sovereign country or state.
AM radio signals bounce around at night, unlike FM. The AM waves bounce off the ionosphere after sunset, and you might hear a station in California while driving in New Jersey.
FM signals do not bounce because they travel in a straight line of approximately no more than 100 miles — due to the curvature of the earth at that range.
Key Illustrative Thoughts:
• “turn your radio on”
• “tuned into the wrong frequency”
• Oscillating a million or millions of times a second!
• one particular frequency and ignores all the others frequencies
• Does it resonant?
• the world is broadcasting on a lot of different frequencies
• frequency modulation — how often the Lord keeps saying it
• amplitude modulation — how strong the signal is
• theological “pirate” broadcasters
• we can’t pick up that signal — not equipped
• the invisible
• receivers catch and interpret what the signal is carrying
• some are not tuned in
• transmitting another message received by other radios around us
• modern-day theological bouncing
• the local church broadcasts in much more of a limited area – FM
• Marriage: two different frequencies
• stay tuned in
• hearing God
• other broadcasters
• “stepping on” the voices of others
Other Information & Links:
“Radio can be incredibly simple, and around the turn of the century this simplicity made early experimentation possible for just about anyone. How simple can it get? Here’s an example:
- Take a fresh 9-volt battery and a coin.
- Find an AM radio and tune it to an area of the dial where you hear static.
- Now hold the battery near the antenna and quickly tap the two terminals of the battery with the coin (so that you connect them together for an instant).
- You will hear a crackle in the radio that is caused by the connection and disconnection of the coin.
Your battery/coin combination is a radio transmitter! It’s not transmitting anything useful (just static), and it will not transmit very far (just a few inches, because it’s not optimized for distance). But if you use the static to tap out Morse code, you can actually communicate over several inches with this crude device!” — howstuffworks
Link to “A brief history of radio” — https://www.explainthatstuff.com/radio.html