MUSEUM "WAALSDORP"

With the propitious properties serving the antenna and its electrical gain of 27 dB (decibel) a number of interesting experiments were executed.

Within the framework of the Geophysical year, a Troposcatter connection - a radio-connection by means of radio wave reflections against the border layer of the troposphere at about 11 km above the earth - was realised with a transmitter situated on the isle of Tromsö in Norway at a distance of more than 800 kilometers.

The antenna of the transmitter was built with 120 separated dipole-antennas (12 by 10) for the frequency of 150,9 Mc, capable for a transmission-power of 4 KW. Due to the antenna-gain of 28,5 dB a 2,3 MW transmission-power was available in the centre of this antenna. A simple pattern of RYRY-signs, transmitted with the amplitude modulated mode, was received by the Würzburg-Riese equipment and made audible.

By participating in an experiment to ascertain the world-wide propagation past the radio-horizon, the Würzburg-Riese receiver also determined this attenuation was 10 dB every 20 km distance. This was measured at the frequency of 150,9 Mc as well.

Besides researching the different layers of air around the earth as a possible medium for the radio-communication the moon was researched in the sixties to be a possible reflector for radio-communication.

On the 24th of July 1965, a staff member of the Physics Laboratory RVO-TNO was successful in making contact with a radio station in the United States of America by way of the moon. With a self constructed transmitter on the 70 cm wavelength and a receiver in connection with the Würzburg-Riese antenna of his employer he succeeded in making a connection with this amateur radio-station.

In the domain of radar the Americans preceded us with the use of the moon as a reflector. In September 1945 a project named "project Diana" was started to develop a radar system that was able to transmit radio-pulses to the moon and receive the echoes of these pulses back after about two seconds. With 0,25 second pulses on a frequency of 111,5 Mc and a peak-power equivalent to 3000 Watt during that 0,25 second, the connection was realised.

The first receipt ever in the Netherlands of images of the earth as seen from space took place on the 31st of August 1964 using the Würzburg-Riese antenna as receiver. These images were transmitted by the American satellite named NIMBUS-I (more information: 1, 2).

At the upper- and lower side of the photograph interference in the received signal is visible. This interference was caused by respectively the appearance and disappearance of the polar satellite NIMBUS I from and behind the horizon of the earth. The satellite moved at a 1000 km height over the poles of the earth.

On the 435 Mc frequency, a telegraph connection with Puerto Rico in South-America was realised. In July of the year 1965, the moon served as a reflector to transport the radio-signal over a distance of 770000 kilometers. The 330 m diameter of the dish reflector of the ARECIBO Observatory in Puerto Rico served as the station at the other end. The received power of the signal was their only 10^-25 part of the transmitted power.

With the aid of several other military satellites, connections were established with other NATO-nations within Europe. Also radio-connections with various Navy vessels were made using the Würzburg-Riese equipment as a transmitter-receiver station in the Netherlands.