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What is the Difference Between FM and AM Radio?

The biggest difference between FM and AM is how the carrier wave is altered or changed. AM is basically constructed to include sound, whereas with FM it is all to do with frequency and the amount of times the signal changes direction. In this blog we look a little deeper into the differences between FM and AM in terms of radio. Most lay people listening to their radios change between FM and AM to hear their favorite radio shows. Normally chat and talk shows are hosted on AM frequency whilst music shows are broadcasted on FM. This all may be true, but it is not the rule.

Basically FM and AM work in the same way, and the biggest difference is in the modification in the carrier waves. Radio is such an important medium for not just entertainment but also as a public information service, it can be used where TV and internet cannot go and in many cases AM is the only way broadcasts can be heard.

AM Radio

Amplitude Modulation (AM) is when the radio signals change to adapt to the sound information being broadcasted. It is true that FM also has alterations to its amplitude but they are not of the same scale as in AM. Any changes in amplitude can be heard more easily because they suffer more from static that can be clearly heard. So when you adjust your radio dial when listening to AM, you can audibly hear the changes in amplitude, and far away broadcasts are very weak with a great amount of static disturbing the signal.

FM Radio

Frequency Modulation (FM) changes the sound through changes in frequency. Both AM and FM signals are effected by alterations in amplitude but when listening on FM they are not as obvious. A broadcast in FM does also have amplitude modulations but they are rarely noticeable because the signal is directed to the listener through frequency changes and not of those of amplitude. So moving you dial whilst listening on FM the antenna is moving through frequencies, which results in a much crisper sound with hardly any static whatsoever, unlike AM and amplitude problems.

Pros and Cons of AM and FM

So which is the best, AM or FM?

To be honest there are pros and cons to both, but the quality of sound that FM radio gives you is the most defining characteristic. As after all we all listen to the radio to hear quality music and voice broadcasts.

AM comes into its own when there are many radio stations trying to broadcast over the same frequency. As AM has a lower bandwidth then it can carry far more radio stations than FM can. This is particularly important in large conurbations and cities as everybody is trying to broadcast at the same time. Also, in such packed towns and cities, trying to get a license to broadcast on FM that is already full of radio stations can be highly difficult, and sometimes the only solution is to broadcast on AM.

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