MTR

Analogue AM FM radio will be here to stay, Digital unpredictable, unreliable

In recent times, digital radio has been trumped as the exclusive successor to analogue radio, almost the be-all and end-all. But is it?

Analogue radio (AM and FM) has been in use for decades (and almost a century for AM!). Whilst FM has proven itself to be the most radical improvement over AM, digital radio is not what it is spruiked up to be. In terms of reliability, DAB and DAB+ is not the improvement over FM that FM was over AM.

Also, there are billions of analogue receivers throughout the world. An AM/FM receiver bought from one part of the world can be taken to another country and would still work perfectly. But digital radio is a completely different matter. Try taking a DAB receiver from the UK over to the US - you guessed it, silence!

The rise of digital

Around the mid 1990s, the United Kingdom's BBC started trialling one of the world's first commercial digital radio standards, DAB. At the time, it was one of the most technologically advanced standards, using the MPEG Layer 2 codec which provided a good level of lossy audio compression. Of course, when citizens pay a receiver licence fee (radio tax), the government can afford to develop and adopt a completely new standard not seen anywhere else in the world.

Newer digital standards, compatiblity issues

As newer, more efficient audio compression methods became widespread towards the late 1990s and early the 2000s, the MP2 codec used by DAB quickly became dated. Eventually, a new digital standard was introduced, namely DAB+ (DAB Plus). The Plus standard uses the AAC+ codec, which is about twice as efficient as MP2.

Older DAB receivers are not able to decode the newer DAB+ signals, due to the new standard not being backwards compatible with the existing standards. Only newer DAB+ receivers can decode both the older and new 'Plus' formats.

The UK's BBC is now considering switching over to the Plus format completely, which could potentially render hundreds of thousands of DAB receivers obsolete.

And Australia, at one time considered a slow adopter of technology, suprisingly decided to implement DAB+ straight off the bat when it started establishing the national digital radio networks.

There have been cases of UK citizens migrating to Australia with their DAB receiver only to find it completely useless here, and having to purchase the 'plus' type to continue listening.

Not forgetting about the other digital transmission methods, the Digital Radio Mondiale (DRM) standard also uses the AAC+ codec. DRM is popular with worldwide shortwave broadcasters. Unfortunately, because many local broacasters chose to use other standards (DAB and iBiquity), DRM never really become universally accepted for local and long distance broadcasts.

Other countries using hybrid, backwards compatible standards

The United States took a completely different approach to digital radio. iBiquity's Hybrid Digital (HD) Radio is the standard used there. Rather than transmitting a completely new digital-only signal on a new frequency band, the digital information is modulated onto a sub-carrier of existing analogue AM and FM transmissions. When reception is good and the signal is clear, HD Radios use the analogue signal for their primary sound reproduction, with the digital part of the signal used to 'enhance' the analogue one. Other alternatives include transmitting sub-channels that are digital only, completely relinquishing the analogue signal to make way for a purely digital transmission.

When the signal is weak or unreliable, the receiver automatically drops back to analogue-only reception, ignoring the digital data. At least with the iBiquity system, the audio won't cut out completely, like it does with DAB.

Older analogue receivers are still able to receive the HD Radio signal, except they won't use the digital subcarrier. This system is an example of backwards compatibility at its best, and one that won't force people into buying new digital radios that could become obsolete in a matter of years.

Digital standards not 'standard' throughout the word

Because the entire world does not use any one single compatible digital format, digital receivers bought in one region are restricted to operating in that region only. As standards change and become upgraded over time, and with each country's governments deciding the standard they wish to adopt, the problem could get worse over time.

Car manufacturers reluctant to go digital

Car manufacturers are also reluctant to fit digital radios as standard, knowing the risk of technological obsolesence. It may even be that the digital radio fitted could become incompatible with future signals, well before the car is due for the scrap heap. Fitting a tried-and-tested AM/FM radio is far less risky, and can be guaranteed to work for many decades.

Digital standards do not stand the test of time

As mentioned earlier, AM and FM radio has been around for generations. There have been minor improvements over time, but all of them retained backwards (and forwards) compatibility. An analogue receiver manufactured 50 (or even 70) years ago would still operate fine today.

But as can be seen with digital radio, the constant change in technology means that no one digital standard will stay for the long haul. DAB had a useful life of about 10 - 15 years. It is not known whether DAB+ will also last as long, considering newer and better audio compression technologies will no doubt become available in the near future.

AM/FM here to stay

The long-standing analogue AM/FM broadcasts will stay for at least the next few decades. There are still far more analogue receivers being manufactured than digital sets. The price difference between the two, as well as the risk of technological obsolescence, makes digital a far less attractive option.

See also: Why DAB+ is bad

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