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A Guide to the Differing Frequencies in Portable Radios

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A Guide to the Differing Frequencies in Portable Radios

"This is London" was the historic sound that heralded the birth of organised public radio in 1922; 18,000 listeners who tuned into the medium waveband radios heard it. The British Broadcasting Company is said to have started the entertainment revolution using the famous Aldwych 2LO broadcasting in London, paving the way to an important stage in the broadcasting industry that happened many years later—the golden age of radio.

Portable radios, which were developed in the 50s, became the most ubiquitous broadcasting medium from the 60s up to the 70s, but even today, households and establishments still tune into a portable radio for news and music. There are thousands of radio frequencies that permeate the air, and a radio has a tuner that picks up a certain frequency range. A discussion about how a portable radio collects frequencies and the differing frequencies in portable radios is important for buyers to have a better understanding on how radios and frequencies interact.

Portable Radio

Portable radios, following its inception in 1954, became the most popular electronic communication device until the 70s. From the 60s to the 70s, the general consumers, fascinated by the device allowing them to tune in to AM and FM broadcasts anywhere they went, bought billions of portable radios. Although the original portable radio peaked and declined towards the end of the 70s, the concept of portable music and radio has been present in other gadgets until today.

The First Portable Radio: Regency TR-1

The companies Texas and Industrial Development Engineering Associate (IDEA) and Texas Instruments of Dallas created the first fully-functional portable or transistor radio, the Regency TR-1. Texas Instruments originally designed the electronic communication device and tried to pitch it to major radio manufacturers, such as RCA, Philco, and Emerson to make the product a mass-market commodity, but the industry giants were not thrilled about the concept.

The president of IDEA, Ed Tutor, saw things differently and jumped at the opportunity to manufacture the TR-1, predicting that they could sell 20 million portable radios in a matter of three years. The TR-1 was released to the public in November 1954 and sold 100,000 units in a span of one year. According to Billboard in 1954, the TR-1 consists of four transistors: one acts as a combination mixer-oscillator, one as an audio amplifier, and the two as intermediate-frequency amplifiers.

The Second Portable Radio: Raytheon 8-TP-1

The company Raytheon introduced the second portable radio, the 8-TP-1 in 1955. The 8-TP-1 was larger than its predecessor, with eight transistors and approximately 10 centimetre speaker. The device has better sound quality than TR-1, and it is also praised for its efficient battery consumption. After the success of Raytheon's portable radio, Zenith, RCA, DeWald, and Crosley also produced alike models.

Modern Applications

The traditional transistor radios fell into decline towards the end of the 70s; however, the feature that allows people to tune into AM and FM broadcasts never left the succeeding portable audio devices. The Walkman cassette players of the company Sony became the most-coveted portable audio device in the 80s, and its later developments include a tuner that captures radio frequencies, very much like the capability of traditional transistor radios, only Walkman brands have an additional cassette tape-playing capability.

When CDs replaced the cassette tapes in the minds of consumers, portable CD players became a common item in the pockets and bags of music lovers. There are CD players, just like Walkman cassette players that include an AM/FM feature. Today, digital audio players also carry the ultimate function of transistor radios. Even computers with an Internet connection can funnel in broadcasts from radio stations. Traditional transistor radios that exist today are very useful devices, and those that can run on batteries are an essential item when there is a power outage.

How Portable Radios Pick Up a Frequency

Portable radios receive radio signals through its antenna. The antenna of a portable radio does not discriminate any frequency, and it can be quite a problem if there is no type of subsystem that allows the radio to zero in on a particular frequency or range of frequencies. The resonator in a radio tuner does the job; it amplifies oscillations within a particular frequency band so listeners can only hear the signals coming from that band. As the resonator amplifies the oscillation of that frequency band, it reduces oscillations at other frequencies so listeners would not hear them.

Different Radio Frequencies

Radio frequency is a rate at which the resonator oscillates to correspond to the frequency of radio waves and alternating currents that carry radio signals. The term radio frequency can also refer to the use of wireless communication as opposed to communication using wires. There are 12 types of radio frequency ranges, with each frequency range varying in wavelength. Out of the 12 types of frequency ranges, two are generally used by radio broadcasting: the very high frequency (VHF) for FM broadcast, and medium frequency (MF) for AM broadcast.

Very High Frequency (VHF)

The use of very high frequency with electromagnetic waves from 30 to 300 MHz goes back to the early 20th century. The International Telecommunications Union (ITU) standardised the name. In the hierarchy of range of frequencies, VHF is above the high frequency (HF) and below the ultra high frequency (UHF). FM radio is broadcasting at frequencies ranging from 88 to 108 MHz. Aside from radio broadcasting, VHF is also used in television broadcasting, land mobile stations for business, military, private, and emergency purposes. It is ideal for short-distance communication, such as radio broadcasting, because its range is just relatively farther than line-of-sight from the transmitter.

Unlike UHF, VHF does not bounce back from the ionosphere, so the transmission is limited to local radio horizon, which is shorter than 100 miles. Although hills, mountains, and other naturally-occurring borders can block VHF, buildings affect it less. In the U.K., FM stations ends in 0.0, 0.2, 0.4, and 0.8 MHz. Some countries use the 0.1, 0.3, 0.5, 0.7 and 0.9 MHz, while others use 0.05, 0.15, 0.25 up to 0.95 MHz.

Medium Frequency (MF)

This frequency band is in the range of 300 KHz to 3 MHz. In European countries, the AM broadcast band ranges from 526.5 to 1606.5 kHz. The propagation of MF wavelengths can be through skywave or groundwave. Groundwave, which broadcasting stations utilise, follows the shape of the earth, and the wavelengths ripples several hundreds of miles from the transmitter, even extending more if the ground is damp or if there is a body of water in the area.

In skywave propagation, radio waves shoot towards the ionosphere and reflected back to earth. The ionosphere consists of different layers, with layers E and F the optimal place for radio waves to hit and bounce back below, but sometimes the noise in layer D absorbs or disrupts the journey of radio waves. During late at night, particularly in winter months or at times of low solar activity, layer D ionosphere virtually disappears, making it easier for skywaves to reach layer F and bounce off hundreds or thousands miles back. AM broadcasting is vulnerable to electrical and atmospheric interference. For this reason, AM channels these days are chiefly for news and talk radio programmes. Music radio and public radio had long shifted to FM channels in the U.K.

Key Comparisons Between VHF and MF

The table below shows the main difference between VHF and MF frequencies. VHF is for FM broadcast, while MF is for AM broadcast.

Type of Frequency

Very high frequency (VHF)

Medium frequency (MF)

Frequency

30 to 300 MHz; particularly, 88 to 108 MHz for FM broadcast

300 kHz to 3 MHz; particularly, 526.5 to 1606.5 kHz for AM broadcast

Wavelength

1 to 10 m

100 m to 1 km

Quality

Clearer broadcast

Susceptible to static

Transmission

Restricted to local radio horizon

Skywave and groundwave

The table can be a quick reference guide to learn about the differences between VHF and MF. There is a considerable gap between the range of frequencies of an FM broadcast and that of AM broadcast.

Reasons for Differing Wavelengths Between AM and FM Frequencies

It is easy to notice the large gap between the range of wavelength of AM radio and FM radio. Why FM frequency band is from 88 to 108 MHz, while that of AM is from 526.5 to 1606.5 kHz. This can all be explained when looking back in history. AM radio was first to come on air, in the 1920s particularly, and because the technology for radio and electronic devices was rather lacking at that time, the frequencies allocated to AM radio were relatively low. Edwin Armstrong introduced FM radio about two decades after AM radio came on air, but it only became popular in the 1960s. For this reason, the frequencies for FM radio are at a much higher range.

Digital Audio Broadcasting (DAB)

One thousand and two stations worldwide use DAB radio technology, with the concentration in European countries. The Norwegian Broadcasting Corporation launched DAB on June 1, 1995, while BBC and SR broadcasted DAB digital radio in September 1995. Just like digital TV broadcasting, DAB also allows more radio channels in the space of one analogue FM channel.

Advantages of DAB

DAB radios automatically capture all the available stations, providing users a list to choose from. DAB standard lessens the consequences of signal noise and multipath fading, which are common to analogue FM radio. In addition, DAB transmissions do not have a hissing sound that listeners hear on analogue radio. Cities like London may carry many pirate radio stations, but these stations cannot intercept with the DAB broadcasting equipment, allowing listeners to receive more legitimate radio stations.

Disadvantages of DAB

Compared to an analogue FM station that gradually degrades reception with the decreasing signal, DAB reception degrades rapidly when the signal strength plummets to a critical threshold. Furthermore, the compression method that leading countries that use DAB employ is utilised to a certain extent that the broadcast has lower sound quality compared with non-mobile FM broadcasts. Despite this problem, a survey of DAB listeners has shown that DAB is on par, if not better, with FM when it comes to reception quality. Because of the digital processing of signals in the radio, there is a two- to four-second delay of broadcast depending on the decoding circuitry used. DAB is a new technology, so its coverage is less than FM coverage.

Buying Portable Radios on eBay

Any home or office should have a portable radio. If you are currently planning to buy a portable radio, it is very easy to do so on eBay. With minimal searching, you can find a portable radio that meets your requirements. What is great about eBay is that you can find new and refurbished products of various kinds.

In addition, there are different brands to choose from on eBay, so whether you fancy Pure, Sony, Roberts, Llyotron, Bush, Eton, or any other brand, you can find it on the site. A portable radio carries different features, and you can add a specific feature to your keywords when searching on eBay. You can choose from radios that are battery-operated or AC powered or ones with a digital or analogue display by using the filters. Just remember to deal wisely on the site. Choose a seller that has consistent positive buyer feedback and a return policy.

Conclusion

A portable radio is an essential electronic device in people's lives. Not only does it provide people with music any time of the day, but in situations when there is a power outage due to a storm or hurricane, a battery-operated portable radio is very useful to tune into news. A portable radio, as it name suggests, can be brought anywhere, so it easy for listeners to listen to music, news, and other radio programmes wherever they are.

Mainly, there are two different frequencies in portable radios: very high frequency (VHF) for FM radio and medium frequency (MF) for AM radio. FM has clearer reception than AM, which is why many stations have long shifted to FM. Digital Audio Broadcasting or DAB is a relatively new technology, and although listeners are generally satisfied with it, it is still not on par with FM when it comes to quality based on industry standards. Knowing the advantages and disadvantages of each helps buyers gain better understanding about how a radio station and the portable radio itself works.

 
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