Blog Post #2 - How The Technology Works

Let's recall... Low Power FM radios are locally based nonprofit frequencies that have to avoid full-power FM stations in order to minimize interference. (http://arstechnica.com/tech-policy/news/2009/03/a-comeback-for-low-power-fm-radio.ars)

Graphic from http://spindelvev.net/gallery/d/514-4/radio.jpg

Let's start with the basics.

1. What is a radio? According to the Wikia Engineering website, a radio is the "wireless transmission of signals, by modulation of electromagnetic waves with frequencies below those of light." ( http://engineering.wikia.com/wiki/Radio)

2. What are radio waves?

Radio waves are a form of electromagnetic radiation that gets created as a result of a charged object that accelerates with a frequency that lies in the radio frequency (RF- This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves) portion of the electromagnetic spectrum. This ranges from a few tens of Hz (hertz) to a few hundred GHz.

Electromagnetic radiation travels through oscillating electromagnetic fields that pass through the air and the vacuum of space. It does not require a medium of transport. When radio waves pass an electrical conductor, the oscillating electric or magnetic field (depending on the shape of the conductor) induces an alternating current and voltage in the conductor. This can be transformed into audio or other signals that carry information.

It is interesting to note that...

Although the word 'radio' is used to describe the above phenomenon, the common transmissions we know of today as television, radio, radar, and cell phone are all classed as radio frequency emissions.

How is a radio signal created, transmitted and received?

Important terms:

Wavelength - distance from crest to crest of a wave

Frequency - the number of waves passing a given point a second.

Electromagnetic wavelengths are measured the same way.

Radio signals are usually in the form of AM or FM radio transmissions.

AM RADIO

AM radio takes the electrical image of a sound source to modulate the amplitude of a carrier wave. At the receiver end in the detection process, that image is stripped back off the carrier and turned back into sound by a loudspeaker. (http://hyperphysics.phy-astr.gsu.edu/hbase/Audio/bcast.html#c3)

FM RADIO

According to the diagram on the left, FM radio takes the electrical image of a sound source to modulate the frequency of a carrier wave. At the receiver end in the detection process, that image is stripped back off the carrier and turned back into sound by a loudspeaker.

Diagrams and text from http://hyperphysics.phy-astr.gsu.edu/hbase/Audio/bcast.html#c3

Simple signal transmissions can be done by something called straightforward amplitude modulation or frequency modulation. More complex transmissions require a signal upon a carrier wave that produces sidebands arising from the sum and difference frequencies.

Radio transmission

When electromagnetic waves come in contact with an antenna, they create a voltage (potential) in the antenna circuit which alternates (travels back and forth) with the frequency of waves, assuming that the circuit is of proper length. It is important for the circuit to be of proper length. In order to adjust the electrical length or tune it, a "Tuning Coil" is placed in the antenna circuit and connected to the ground. The coil is adjustable by which the number of coil turns is increased or decreased, thus changing the electrical length of the antenna circuit. By this adjustment the antenna frequency is tuned and synchronized with the frequency of the electromagnetic wave length which it is desired to receive. If not properly tuned, the antenna potential alternations (frequency) and the electromagnetic wave frequency clash.

FINDINGS

The search tool you used and why

I used Yahoo because I wanted to see if any of the search items from this search engine would have similar results to ones I found on Ask.com in the last project. I also want to explore what Yahoo has to offer that Google doesn't. I like how there is a tab on the side that has options for showing only Wikipedia results or if you want to show all results. The exact search terms you used

"Radio signal transmission" "Radio signal fm" "Low power fm technologies"

The two best sites you found:

Critical Past - http://www.criticalpast.com/video/65675043000_Radio-transmission-and-Reception_coil-with-pendulum_filament-circuit_sound-waves

Wikia - http://engineering.wikia.com/wiki/Radio

What individual or organization is responsible for the site and what is their purpose or mission?

CriticalPast.com was formed by a team of archival research, film, and Internet professionals, that decided to create the largest privately held online archival footage sources in the world. The collection includes thousands of hours of video, millions of still photos, and more.

Wikia is a collaborative publishing platform that allows individuals and communities to discover, create and share content on any topic in multiple languages. It is not the same as Wikipedia, as Wikia focuses on being the true resource on many topics that do not fit into the typical encyclopedia model, so it builds its communities around pop culture content.

How is the site funded? No information on how the site is funded.

How current is the information?

Critical Past - uses clips from 1941, however there is no need to be current with the technicalities behind radio transmissions as it is a rather old concept. However, as for the site itself, it is fully maintained and kept up to date until today.

Wikia - no definite publishing date of information, however most current source used in Wikia for the Radio page is 2003.

What useful information about how your technology works is there on the site? Be sure to note any useful images and diagrams that would help explain and translate technical information for an audience of your peers.

Critical Past - It had a wonderful (but old) clip of how radio transmission and reception worked, which helped better my understanding of the technology behind radios. Easy to understand. Full of information.

Wikia - This website broke down the topic into different sub-categories that made it easier to understand the overall idea behind radios and how their signal transmissions work.

Given your answers to the questions above, what kind of information might be missing or unreliable on the site? What other kinds of sites should you search for that might provide the missing information?

Critical Past - no mention of any new advancements in the technology as the mission of the website is to provide an archive of old footage and films that can help us understand our world today better. It might help to go to a site with more recent updates on the technology to gain a more holistic perspective on our topic.

Wikia - No diagrams that helped illustrate the points being made. It would be more helpful to go to a less information-dense website to find diagrams that will help support the research being made.

Other websites

Arstechnica - http://arstechnica.com/tech-policy/news/2009/03/a-comeback-for-low-power-fm-radio.ars

Hyper Physics - http://hyperphysics.phy-astr.gsu.edu/hbase/Audio/bcast.html