Licensed to listen - first radio broadcast in Germany

Prof. Dr. Dietmar Tutsch on the birth of German radio in 1923

October 29, 1923 is considered to be the birth of German radio. Three components were necessary for this, namely sound recording, transmission and, of course, reception. The first usable sound recording process came from Thomas Alva Edison and was already almost 50 years old at the time. How did he succeed?

Tutsch: Mr. Edison had the idea of applying tin foil to a roller. Then, using a needle into this paper with a membrane at the other end and a funnel, he was able to make a recording by transferring these acoustic vibrations of speech via this needle into mechanical waves, through the depressions that were created in the foil. The playback then goes in the opposite direction. These depressions make the membrane and the needle vibrate and you hear it at the end of the funnel.

The invention of the microphone was then the next step to achieve transmission. That's where the development of the telephone also played an important role, didn't it?

Tutsch: Yes, for the telephone, of course, you first need a microphone to be able to convert the speech accordingly, because a microphone transfers air vibrations, i.e. sound into electrical vibrations, in contrast to this phonograph that I just mentioned, where it's mechanical vibrations. So here we have electrical vibrations, and this is done by different techniques, so two variations. Either the membrane generates a current by its movements in a so-called static magnetic field -this is called induction and is an electrotechnical principle- or, the membrane is part of a plate capacitor, and by the vibrations its capacity changes and thus also the current flow. I.e., in the end you transmit sound in current changes, flowing current changes, and you can transmit that over thousands of kilometers, unlike normal sound, which only travels a few meters.

And then there's the reception. There in history is Guglielmo Marconi, who is considered the inventor of radio and patented the commercial use of electromagnetic waves for transmission. He also owed his success to the German physicist Ferdinand Braun, with whom he was even awarded the Nobel Prize in Physics in 1909. How did the transmission work?

Tutsch: The telephone is still wire-bound, so we need a cable. Electromagnetic waves have the advantage that they propagate in air and even in a vacuum. These are coupled electric and magnetic fields. Light also belongs to this kind of fields, only with a different frequency range, than the radio waves. A frequency range means the speed of the oscillations is different. With the electromagnetic waves it is now so that a current changing in time, which flows through such a cable, produces an electromagnetic field. A cable produces only a poor electromagnetic field, but this can be optimized by an antenna. So if you transmit speech with a microphone into such an electromagnetic wave, you can propagate it through the vacuum or the air. At low frequencies, which includes speech, this is very strongly attenuated, the wave does not travel very far. The trick is, one uses very high frequencies and the actual speech is integrated there into these high frequencies. This is called modulation. You can imagine that the intensity of the wave changes with it. With a sound wave, for example, the volume would then be changed. And in the case of an electromagnetic wave, it is the amplitude (amplitude is a term used to describe oscillations, editor's note) that is changed.

"Attention, attention! This is the Berlin broadcasting station, at Vox Haus. On wave 400 meters. Ladies and gentlemen, we are informing you that today the entertainment broadcasting service will begin with the distribution of music performances by wireless telephone," were the first sentences addressed to the listeners by Friedrich Georg Knöpfke, then director of Funkstunde Berlin. However, in order to obtain a so-called "Hör-Gewährung", i.e. a license, customers had to dig deep into their pockets. Why?

Tutsch: We have to remember that 1923 was the time of inflation, not to say hyperinflation, as it was called, and the license to listen to the radio cost 780 billion paper marks. For comparison, a kilo of rutabagas cost 300 million paper marks at that time, so it was already a relatively large amount of money. You could say that this license was something like the forerunner of today's GEZ.

After that, development proceeded at breakneck speed. On January 31, 1925, the first shortwave radio broadcast from the U.S. could already be heard in Germany. And on November 15, 1926, the World Broadcasting Association allocated radio frequencies worldwide for the first time. Why was that important?

Tutsch: As I said, in Germany you could hear the radio from the USA, i.e. the range of these radio waves was and is very large. Therefore, the countries had to agree among themselves who could use which frequencies, otherwise the individual radio stations would overlap. It's like at a big party where lots of people are talking and everything overlaps. You can't understand anything afterwards. That's why this ordered frequency range served to ensure that the radio could be heard internationally. All stations were assigned an exclusive frequency range.

Then came the time of the short wave experiments. What is the difference between shortwave and longwave?

Tutsch: Due to their frequency range, short waves have the advantage that the waves can reach the high-altitude ionosphere (the ionosphere is that part of the atmosphere of a celestial body which contains large quantities of ions and free electrons. The ionosphere is that part of the atmosphere of a celestial body which contains large quantities of ions and free electrons. I.e., one gets from one half of the earth to the other half, in contrast to long and medium wave. These are so-called ground waves, which only propagate along the earth's surface. They can overcome a certain curvature of the earth, but they only travel a few hundred or thousand kilometers.

After the war, the frequencies were renegotiated; Germany, as an occupied nation, received only very poor medium-wave frequencies and from then on used ultra-short wave (VHF).

Tutsch: Since medium wave with the amplitude modulation already mentioned is very susceptible to atmospheric interference and you have poor sound quality, after the war they used the frequency modulation of ultra-short wave because it has good sound quality that still meets today's standards.

And today? Has the Internet overtaken radio?

Tutsch: Yes, you can definitely say that. Streaming is everywhere today, all stations offer their programs on the Internet, and the Internet is available worldwide, which has made long-medium and shortwaves uninteresting, also because of the poorer sound quality. Radio is actually only interesting in the FM range. There we have a quite high sound quality, and the advantage here is that you can use local stations for mobile use, i.e. in the car or on the construction site. Especially there it still has its raison d'être.

Uwe Blass

Prof. Dr.-Ing. Dietmar Tutsch is head of the Chair of Automation Technology / Computer Science in the Faculty of Electrical Engineering, Information Technology and Media Technology at Bergische Universität.