As the populace becomes used to things
being switched off (analog TV, various generations of mobile phone service,
etc.), the question arises, particularly among vintage radio enthusiasts,
"Will AM radio be turned off?". The short answer is eventually, yes. In
fact, the process has already begun in regional areas.
There's several reasons behind this:
Regional AM to FM Conversion.
AM stations in regional areas are being turned off right now. The ACMA has since 2016, promoted a conversion of regional stations from AM to FM. I first became aware of this when one of my nearby regional stations, 2BS in Bathurst, started advertising the closure of its AM transmitter at the end of 2018. I recorded what I could of the event, but unfortunately reception conditions at the time were poor.
As of July 2023, these stations have already closed their AM transmitters:
For NSW, we see that 2AD, 2BS, 2EC, 2XL, 2GN, 2GF, 2ST, 2RE, have already closed down.
The table below shows the NSW stations which have requested FM conversion as of September 2022. In NSW, this will end AM transmissions from 2RG, 2MO, 2NZ, 2LM, 2LT, 2VM, 2MG, 2PK, 2TM, 2WG, and 2LF.
As of September 2022, these stations have yet to 'convert'.
When 2CH switched to DAB only, it shut down after 18 months.
It's an undeniable fact that of the radio audience, young people don't listen to AM broadcasting. When was the last time you saw someone under the age of 50 listening to AM? Young people are not interested in listening to horse racing or the football. Young people use social media rather than talkback radio to get their point across. AM radio stations do not play music that young people like.
Let's do a quick analysis of what's on offer in Sydney:
ABC Radio; stations 2FC, 2BL (currently called 'Radio National' and '702 ABC' respectively), and 2PB (currently called 'Newsradio'). Most young people are not interested in arts and science on 2FC. 2BL is talk all day, and nothing really of interest to young people. 2PB is news and parliament.
2GB. Talk only, and a lot of advertising
about health problems, aged care, and funerals. News repeated every half
hour during the daytime.
2UE. The one remaining music station, playing mostly 60's and 70's music on a limited playlist. Again, advertising emphasis is on getting old and sick.
2KY. Horse racing.
2EA. The old 2UW transmitter. Run by the Special Broadcasting Service, this is ethnic programming in foreign languages.
SEN. Previously 2CH, which was a music station of the format 2UE is now. When the AM transmitter was taken over by sports station, SEN, 2CH music programming was available on DAB only, until closure 18 months later.
2RPH. Readings from magazines and newspapers for visually impaired people.
2SM. Years ago a top rating music station which appealed to the youth, this is now a talk station similar to 2GB, and is relayed to many regional stations.
In rural areas, the programming tends to have some local content in the morning, and then afternoon and night programming might be taken from 2GB or 2SM.
With that choice, is there is anything to appeal to the under 50's masses?
This is what will be the end of radio broadcasting, in all its forms, AM, FM, and shortwave. Already, a few years ago the Radio Australia shortwave service was shut down. Apart from high power Chinese and U.S. religious broadcasters, there isn't really much left on the SW bands.
On a more local level, internet streaming is now so mainstream, that both AM and FM listening is in decline (as is off air TV, but that's another topic).
There's a good reason for that. Radio stations don't play what listeners want. Conservative formats, limited and repetitive playlists, excess advertising, constant babble, and news every hour to interrupt the programming, are all turn offs.
Compare that to a playlist of music with every track being one that you like, with no babble, and if there are ads, they are short and non intrusive. The choice between the two is obvious.
What about news? Young people get that by scrolling through social media on their mobile phone. They don't want to listen to someone reading the same thing out every hour.
AM transmitters need lots of real estate. While the tower itself doesn't take up much ground area, the guy wires do, along with the earthing system. Also sufficient area has to be provided in case the tower collapses. In an increasingly densely populated city like Sydney, this is a problem.
In Sydney, the commercial AM transmitters are located in an area of otherwise high density living, at Homebush. As Sydney becomes overtaken by blocks of flats, the AM transmitters are now in the way. Developers want them gone. And as any Sydney resident can tell you, developers always get their way. One temporary solution has been to share two transmitters with one tower. Unfortunately, this is a compromise, since the tower performs better with one wavelength than another.
Beloved of the manufacturers of anything electronic in the last 30 years or so, is the switchmode power supply. Iron cored transformers and linear regulators have succumbed to political correctness. They are not, to use the buzz words, as "energy efficient" as switchmode types.
Instead, the reliable and electrically clean power supply is replaced by something a lot smaller, lighter, and cheaper, but which not only distorts the mains waveform, also radiates a lot of RF interference. Unfortunately, this interference happens to be concentrated at around 50 to 100kHz. Not surprisingly, the harmonics are very strong in the AM broadcast band.
It's not just switchmode power supplies, but also radiation from microprocessors switching at ever higher speeds.
Since the advent of high speed internet, another source of interference for the AM broadcast band has been created, first by ADSL cabling, and then to a worse extent by the NBN which replaced that.
With incandescent lamps also now politically incorrect, the CFL and LED replacement lamps used in their place also have switchmode power supplies. It can be imagined in the evening with a house full of lights on, how much RFI gets radiated. This, along with the plethora of IT and audio visual equipment, all with switchmode power supplies.
The result is AM signals can be made unlistenable unless you're in a strong signal area. The non-technical listener knows nothing of noise reducing aerials.
Poor Quality Receivers.
In the days pre-interference, and when more music was played on AM, the most common reason to switch to FM was because 'AM is shit quality compared to FM'. As the typical non-technical listener sees it, there's a lot of truth in that statement. In reality, it doesn't have to be that way.
The problem is that most commercially made receivers, especially from the solid state era, have a very narrow bandwidth. On top of that, particularly with a lot of battery operated sets, are under-biassed class B output stages, and small speakers. And then there's the mono signal.
Narrow bandwidth comes about because most commercially made receivers, since the early 1930's, are superhets. A superhet is by nature more selective than a TRF type of set. In the early days, 'knife edge selectivity' was a selling point, because in city areas TRF receivers, especially of questionable design, could have difficulty separating all the stations.
In Australia, the geographical isolation of the stations allows the full audio bandwidth to be transmitted. Unfortunately, this is lost with most superhet receivers. The reason is that the selectivity curve of the IF amplifier is determined by cost. With ordinary design techniques, creating an IF strip which allows, say, 10kHz bandwidth would have poor overall selectivity, because the response curve has a widening frequency response as the gain drops off. Typically, a valve superhet might have a bandwidth of 5kHz at the 3db points.
When transistors came along, the situation
was worsened. Per stage, transistors have lower gain than valves. Transistors
were expensive too, so costs dictated using no more than necessary. The
frequency converter saw the return of the 'autodyne' self-oscillating circuit,
so as to eliminate one transistor. To compensate for lower gain in the
IF amplifier, the IF transformers were designed for higher gain, which
of course means a reduction in bandwidth.
A bandwidth of 2-3kHz is not uncommon. Unfortunately, the design of transistor IF amplifiers for AM receivers has remained the same until the present day. The detection stage is usually a diode operating under less than ideal operating conditions, which adds to distortion.
These transistor sets were seen as acceptable in view of the convenience of small size, and long battery life.
Even with supposed "Hi-Fi" tuners, the AM section was always second class, using the same front end as a pocket radio.
A few enthusiasts, aware of the good quality signals being transmitted, have used TRF receivers or wideband superhets, with low distortion detectors. Unfortunately, this is not typical of most listeners.
Along with transistors was a return to the class B output stage, something used in some battery operated valve radios for reasons of battery economy. They're more efficient than a class A output stage, so the battery lasts longer for a given power output. However, distortion is higher. In the case of transistor sets, the output stage is often under biassed, to reduce battery current at the expense of crossover distortion. It is true that there are some transistor sets with class A output stages, but mostly these are car sets, or mains operated.
Then there's hopelessly inadequate loudspeakers. After all, one of the selling points for transistors was miniaturisation. Pocket size receivers naturally had pocket size speakers. And there's no way that can be good for low frequency response. Furthermore, the designers knew there was no low frequency response, so restricted the bandwidth of the audio stage too. Bass response of the audio is often reduced for two reasons. It means the output stage is not wasting power for something that wasn't going to be heard anyway on a small loudspeaker. Also, the sound appears 'brighter' by emphasising what little high frequency response remains.
Along with miniaturisation and portability, the ferrite loopstick aerial became a feature of most receivers. Directional in nature, it means the receiver is not always orientated for maximum signal pickup. Worse still, the receiver might be orientated for maximum noise pickup! Then of course, the shorter the ferrite rod is, in the name of cost and/or available space, the lesser is the signal pickup anyway.
Most transistor sets followed the same format, narrow bandwidth with distortion. It's cheaper to make them this way too, of course. And so we had a generation who only knew this kind of AM sound. When they hear a valve radio with its larger speaker, class A output stage, and wider bandwidth, it's not uncommon to hear the 'valve radios sound so much better' comment.
AM stereo was an attempt in the mid 1980's
at clawing back some of the audience from the stereo FM stations. It fizzled
out pretty quickly. Receivers were few and far between, and listeners just
weren't interested. Rather unusual were talk stations converting to stereo,
which seemed pointless.
It's all rather unfortunate, because AM stereo through a wideband receiver, was in my opinion, as good as FM. In fact, the channel separation was noticeably better. By the 2000's most stations had reverted back to mono. By then, most music stations had left the AM band in city areas for FM anyway.
It is quite possible to make a wide bandwidth AM receiver, with adequate selectivity, and a low distortion detector. I describe a TRF set with low distortion detector here. But, as always, the buying public wants the cheapest. The fact is that AM does allow some really cheap and nasty designs to be built, while still being acceptable for most listeners. Most listeners have no idea just how good AM can be, having never heard it through a quality receiver. The poor image is stuck with AM forever.
Receivers without AM.
Can anyone name a mobile phone that includes an AM radio? How about a DAB tuner? What about an old fashioned PC tuner card?
And don't forget, as of 2023, AM radios are starting to be dropped from cars. One excuse is that electric cars use a switchmode controller, and with copious amounts of RF pollution emitted, are a difficult environment for AM reception. But the fact that a few electric cars do offer AM reception would indicate the problem is less than it's made out to be. Aside from that, car marketing is aimed at young people - and they don't listen to AM anyway. You'll note that in car entertainment these days is all internet or Bluetooth based, with a radio tacked on as an inconvenient afterthought.
No Duplication of Services.
Unlike in the U.S., Australian radio stations have never been permitted to operate both on AM and FM in the same area. If an AM station wants to transmit on FM, it must give up its AM licence. Examples of this in Sydney during the 1990's were 2UW which became MIX, and gave its AM frequency of 1107kHz to 2EA. Similarly, when 2WS transferred to FM (under the same call sign), its former frequency of 1224kHz was given to 2RPH.
There's no technical reason of course for this policy. It's all political because radio stations feel threatened if their competitors have more outlets than they do. As a side issue, this has a lot to do with why it took so long to get FM operating in Australia. Those in charge of the media have considerable political power.
In the ideal world, AM stations would be able to transmit on FM as well, so that listeners with either type of receiver could listen. Thanks to Australian conservatism, it isn't going to happen.