Idzerda's transmitter technology (1919-1924)

Radio Telephony and frequency modulation
To really grasp the innovative power of Idzerda's PCGG transmitter, we have to get a bit technical. His first radio telephony experiments date back to the 'Jaarbeurs' trade fair in February 1919. Here Idzerda used his own unique modulation system. We generally know of two: Amplitude Modulation (AM) and Frequency Modulation (FM). Idzerda however dreamt up a different kind of frequency modulation (FM) that required no additional power. 
Early FM modulation
Instead of adding an extra radio lamp to his system, Idzerda uses this carbon microphone to bridge part of the grid of the transmitter coil. With this technique sound is converted to frequency variations. It is an extremely ingenious way to create an early form of Frequency Modulation (FM). We call this modulation system "System I".
Idzerda's station in 1920
On November 6 1919 Idzerda starts with the regular broadcasting of radio programs from his home in the Beukstraat in The Hague. In cooperation with Philips he has developed a radio transmitter lamp. You can see this lamp in the Idzerda station as it was in use from 1920 to 1921. The picture shows that this transmitter contains only one lamp. (Center below the meter panel). Visible is the Pathefoon with attached carbon microphone on which he played the records he sometimes even received form listeners.
System II
System I has too many restrictions for Idzerda's taste. The construction of the transmitter requires that the carbon microphone is connected directly to the transmitting light. This means the microphone and transmitter can not be far away from each other. After the development of a modulator lamp this problem is solved. The broadcast signal may then be supplied from a variety of sources via a line connection to the transmitter. This technique is also used to broadcast live music like the Kurhaus Concerts in 1923.
String orchestras
Idzerda strives to broadcast live music. Via telephone wires, he can connect multiple sources to his transmitter. With self-built funnels he amplifies the sound of musicians in his studio. Everything is experimental, so is his studio, equipped with thick curtains, a red light and a warning sign when Idzerda was on air. 

"When this light is on...Shut up", says this warning sign that hung on the wall outside Idzerda's 'studio'.

FM transmitter lost in fire
Commissioned by the KNMI (Royal Dutch Meteorological Institute) in De Bilt Idzerda build a station to broadcast weather reports. This is the only job he ever got to build a transmitter according to his FM system. The KNMI station was decorated for telephony according to System I and II and for telegraphy in "continueous wave" and "tonic train". Unfortunately, this transmitter is lost in a fire shortly after taking it into service. The blueprint resembles the blueprint of the altered PCGG in 1924.
Transmitter performance
The listeners of PCGG live all over the country. With an output of 10 watts, Idzerda gets reactions from listeners from Amsterdam, Nijmegen and Ginniken. Tests with minimal power show that he succeeds to bridge distances of 675 kilometers with a power of just 1 watt! Now in those days, of course, one is little affected by all kinds of broadcast transmitters. The 'ether' is still pretty empty. Even in England a lot of people listen to the station PCGG. The so-called 'Dutch Concerts' are very popular.
Pioneer phase
Idzerda was a true radio pioneer in a remarkable era. He was the first radio broadcaster who managed to broadcast a steady radio program for a period of years. The rise of healthier competition forced his pioneer role to an end. He lost his broadcasting permit in 1924 due to financial problems. In 1930 he regained a new permit, but only to air unannounced during nighttime. By that time Hilversum had become the new radio city.
Guess the age
The transmitter in the depot is difficult to date. Very probably it's from after 1924. The current panel contains many unused holes. We think Idzerda used it during the construction of the KNMI station. This project undoubtedly required experiments and measurements using test circuits. He may have used the panel later to build the station that he broadcasted his congratulatory "night owls"-program with in 1931.
Museum object
After the death of Idzerda, in 1945, his widow donated his transmitter to the former Dutch Postmuseum. Later, she also donated other attributes associated with the transmitter. In 1950, the station was modified and made suitable for demonstrations. Since then, this extraordinary object is regularly exhibited. In this photo you can see the vertical power box of the transmitter as it is now in our collection.
Credits: Story

Production: Carlien Booij, Erik van Tuijn
Research: Pieter Bakker, Jette Pellemans, Carlien Booij, Erik van Tuijn
Art direction: Ruben Steeman, buro RuSt
Camera and video editing: Elmar Kroezen, Videofabrique
Animations: Kirsten Sschuil, Ruben Steeman
With special thanks to: Tobias Idzerda, grandson of Hans Idzerda, Pieter Bakker and everyone involved at Sound and Vision

Credits: All media
The story featured may in some cases have been created by an independent third party and may not always represent the views of the institutions, listed below, who have supplied the content.