A Deeper Look at the Funcionality of Radio

With the previous post I was able to gain insight into the history of radio and how it has evolved today (primarily focusing on the development of LPFM); now I hope to do research upon the functionality of radio in order to gain a greater sense of understanding for the radio as a whole. In order to begin my research I turned to http://www.ipl.org, which is a reliable website designed to answer questions. In the search bar I simply typed in "radio". Upon doing so I was presented with 500 pages of material. I knew that within these pages I would find something of value so I began to skim and soon enough I found http://www.vwlowen.co.uk/radio/howradioworks/index.htm, a detailed website on how radio works. This website is run by John Owen, who lives in the UK. His website is designed to educate people on various technologies. The site is funded and supported by http://www.icra.org, http://www.safesurf.com, and http://www.w3c.org. This source is relevant because its copyright date is 2011 and the information it has on the functionality of radio is clear, detailed, and easy to understand (not to mention it is full of useful diagrams). The only thing that could be missing from this website is, perhaps, the usage of a time-line to detail when certain radio functions were emerging. Despite the lack of time-line, after having analyzed the credibility of this site I decided it would be a perfect source for my research.

Furthermore, I needed to find another useful website that would give me a closer look at the functionality of AM and FM radio. Fortunately, while perusing the first site I was directed to another extremely helpful website, http://www.electronics-radio.com/. This website is especially helpful because it has sections on amplitude modulation (AM) and frequency modulation (FM) which is the next focus of my research. In order to use this website I needed to validate that it is a credible source. While analyzing the website I found out that this site is run by Ian Poole of Adrio Communications Ltd. and the site is funded through Google advertising. Moreover, this site is extremely current featuring daily posts on interesting technological advances or just a random tech fact. It also doesn't hurt that this site is extremely reliable because of all the citations throughout the posts. Another part that caught my attention was the goal of the website which clearly states that, "Electronics and Radio Today contains a vast amount of information, data and articles about basic electronics." Perhaps the only thing missing from this website is their lack of a summary of the functionality of radio. Nonetheless, this is also a very useful and credible source.


Below are my notes on the two websites:

1.  How Radio Works

• radio waves are everywhere
• a radio wave should be the shape of a sine wave
• first device used to make waves: vacuum tube aka thermionic valve
• the vacuum tube was later replaced with semiconductors in form of transistors & integrated circuits
• waves are based around the concept of amplification and positive feedback
• when oscillation occurs it is known as positive feedback
• resonance-the ear-piercing howl sound
• capacitor-"two parallel metal plates separated by a small gap"
• inductor- coil of wire 
• together (refer to image on page 9)... 
1. a capacitor will block low frequencies but let higher ones pass
2. the high frequencies will ground through capacitor, leave low freq's at output
3. with a coil it will block higher frequencies and allow lower freq's to pass
4. will block lower frequencies and allow higher freq's to pass
• frequency modulation-amplitude of radio is fixed and the frequency is varied
• antenna is used as receiver
• antennas used for: VHF/FM, MW, and SW
• radio waves travel at speed of light
• higher frequency=shorter wavelength

2. Amplitude Modulation & Frequency Modulation (From Electronics and Radio Today)

Amplitude Modulation

• modulation form used for radio transmissions for broadcasting as well as two way radio comm
• first modulated signal was transmitted in 1901
• became standard for voice transmissions
• is used for audio broadcasting on the long medium and short wave bands
• AM use is declining
• audio must be modulated to be carried or broadcasted
• the "apmlitude of the signal is changed in line with the instantaneous intensity of the sound"

"Therefore when a tone of 1 kHz is mixed with a carrier of 1 MHz, a "sum" frequency is produced at 1 MHz + 1 kHz, and a difference frequency is produced at 1 MHz - 1 kHz, i.e. 1 kHz above and below the carrier."

Summary: AM is advantageous because of its simplicity but it is not the most efficient

Frequency Modulation

• widely used on frequencies above 30MHz
• well known for its used for VHF HM broadcasting
• can provide near interference free reception
• is far more popular then older transmissions
• used for fixed or mobile radio communication systems
• when signal is modulated the new frequency signal moves up and down
• the amount by which it moves is known as deviation
• it is resilient to signal level variations
• its easy to apply modulation at a low power stage of the transmitter
• is possible to use RF amplifiers with frequency modulated signals

Summary: FM is more commonly used for its greater advantages over AM