Markus and all,
I would add,
AM is receivable with a germanium-radio receiver, a tuned circuit, a diode and a crystal earphone,
an easy project for a young, a good introduction to electronics.
My son was fascinated with it, at his age of 10 or so.
With an addition of an IC AF amplifier the next year, he wrote in his report,
"I was surprised of the big sound coming out of the speaker".
Hideho YAMAMURA, JF1DMQ
As announced before, the German longwave broadcast transmissions on 153 and 207 kHz (Deutschlandfunk) and 177 kHz (Deutschlandradio) will be terminated with the New Year 2015. Presumably mediumwave AM transmissions will follow one year later. It has been claimed that the continuation would be too costly, considering the relatively small number of AM listeners.
Along with others, I think that this is a sad landmark in radio history, because
- AM radio is simple and intuitive. The concepts of AM transmission and reception are easy to conceive, even by a child. And it's motivating to play with it. In a few years, the kids can still build a diode receiver, but listening to the small surrogate oscillator Daddy has hidden behind the sofa will surely not be the same thing!
Then try to explain digital audio broadcasting to your grandson, all the way from end-to-end (microphone to speaker. I even have strong doubts that there is a single expert person now who understands the whole chain. Every engineer is supposed to be working on the details of a small subpart, knows little more than he "needs to know", and communication is done by formal processes and requirement specifications. Of course this is a general trend in industry, but I don't think it is very desirable.
- AM is linear. Listening to 153 kHz in the evening hours, faint Algerian music can be heard in the background. When I was young I was fascinated by those distant sounds, and it probably contributed strongly to my later interest in "DX". You can actually hear that the radio waves have come a long way, experience selective fading, and solar effects, or subtle ionospheric effects like Luxembourg crossmodulation. Modern digital radio considers all this undesirable interference - what you get is either perfect mp3 stereo, or nothing at all.
- AM is a historic legacy. Especially on longwave, each transmitter and antenna coupler is a unique installation, and the antennas are impressive monuments. SAQ is a good example: While it's no longer needed for transatlantic communication, it's still being kept alive as an educative and fascinating world heritage. Why not keep at least one large LF broadcast transmitter?
- LF and MF radio is efficient. The half-megawatt Donebach transmitter probably consumes a million Euros worth of energy per year, and in addition, there is antenna and transmitter maintenance to be paid for. But it provides gapless service across many million square kilometers. Similar coverage with DAB will probably require a thousand or more digital transmitters, which in total may well consume a higher amount of power and secondary costs. One difficulty about keeping LF transmitters alive may actually be there are so few of them - as most engineers seem to be working on software and silicon chip-level hardware, it may become hard to make spare parts and find experienced service people for high-voltage RF in the future.
- Radio helps to protect against spectrum pollution. Members of the LF group are only too aware of the inflation of inadequately filtered SMPS power supplies, "dirty" ADSL and PLC communication over unshielded copper lines, and upcoming threats like inductive e-car charging devices. Currently there are still EMC regulations in place which at least provide some limit on radiated and conducted interference above 150 kHz. But when there are no more AM broadcast listeners, why should anyone invest effort to protect that part of spectrum against local interference? The situation for those few crazy LF enthusiasts who enjoy digging down to the noise floor may soon become comparable to that of backyard astronomers in an urban environment - ie plain frustrating.
Anyway, all the best for the new year,