Panoramic receivers (1953 – 1964)
The panoramic receiver derives its name from the wide overview of simultaneous radio transmitters in a certain frequency range. The use of the panoramic receiver as a means of monitoring a frequency area is of military importance in electronic warfare and the detection of illegal radio transmissions. Panorama receivers are radios, which one can tune to a station just like a normal radio, but which also have a wide display or some displays with an overview of all transmitted radio power in a large frequency range. When someone broadcasts somewhere in that frequency area, it was immediately detected and within two or three seconds one could tune in and listen in. It was also possible to quickly determine a relationship between two transmitters, e.g. an alternating talk-listen operation. Receivers with such a wide frequency display as described in more detail below are very special.
In 1953, the Physics Laboratory TNO developed the panoramic receiver type 1 with a single electron beam tube. A selected range of 500 kHz could be observed between 1.5 and 15 MHz. With the help of separate converters, the frequency range of the panoramic receiver was increased from 0.1 to 1.5 MHz and 15 to 30 MHz, so that the total frequency band ran from 0.1 to 30 MHz.
In 1955, the receiver was equipped with five electron-beam tubes, whereby the various channels can be better distinguished from each other by dividing the frequency scale over several tubes. The presence of a transmitter was made visible by a vertical deflection on a horizontal line on an electron beam tube. That line was divided over more electron-beam tubes placed next to each other in a horizontal row. The location of the deflection, measured from the beginning of the line, is a measure of the frequency at which the transmitter operates. A transmitter was made audible by placing a visible vertical marking of the alignment on the horizontal line.
In 1960, a new type of panoramic receiver system was developed consisting of three units: antenna switch box, panoramic receiver, and power supply. With the switch box, a choice was made between three antennas that together covered the area 30-180 MHz. The receiver was equipped with six contiguous frequency bands of 25 MHz each, made visible on five electron-beam tubes. A sixth tube gave an area of 0.5 MHz around the selected frequency.
Searching radar emissions
Below a picture of a radar transmissions search device built by the LEOK in 1964. The most important parts of the receiver are the antenna, the receiver unit and the presentation unit. The antenna was suitable for receiving signals over 360 degrees of horizontally, vertically and circularly polarised transmissions between 150 to 1500 MHz. The receiver unit offers a choice of four frequency bands: 150 – 240 MHz, 240 – 420 MHz, 420 – 780 MHz and 780 – 1500 MHz. The influence of the noise is minimised by the parametric upconverter used in the input stage with a carcinotron as the local oscillator. The scanning of the band is done by rapidly swaying the carcinotron in frequency. If the frequency of the received signal added to the oscillator frequency is equal to about 10,000 MHz, the signal is presented. The presentation unit linearly displays each band in nine lines on a normal TV tube.