The Sottens transmitter

Switched off in December 2010 (MW) and in November 2004 (SW)


Medium-wave transmitter data

Location:     E 6° 43' 44.27" / N 46° 39' 21.91"
Frequency:     Transmitter is off (used to be 765 kHz).
Wavelength:     Transmitter is off (used to be 392 m).
Power:     Transmitter is off (used to be 600 kW,
downpowered to 150 kW for the last few years).
Call-sign:     Used to be "Option Musique".
Transmission type:     Used to be a medium wave AM broadcast station.

Brief history

The Sottens medium-waves transmitter started its operation on March 25, 1931 with a power of 25 kW on 743 kHz (403 m). In 1933 the power was increased to 50 kW. In 1934, following the Luzern Plan, the frequency moved to 677 kHz (443.1m ). In 1935 the power was increased to 100 kW. In 1949 a new 190 m high anti-fading antenna was installed. In 1950 as a consequence of the Copenhagen frequency plan, the transmitter was moved to 764 kHz (392.7 m) and the power was increased to 200 kW. In 1970 a new transmitter increased the power to 500 kW. In 1978, because of the Geneva frequency plan, the frequency was changed to 765 kHz (392.2 m). The transmitter was replaced again in 1988 setting the power to 600 kW. In 1990 the main antenna was replaced with the current one. The actual spare antenna is still one of the two original 1931 towers. The transmitter was switched off on December 31, 2010 and the main antenna was dismanteled on Aug. 20, 2014.


Main medium-wave antenna

Tower type:     188 m self supporting tower.
Antenna type:     Vertical λ/2 dipole (6 wires around the tower), tower grounded.
Feed point:     Center fed via a coaxial feeder inside the tower.
Lower end of dipole grounded via a variable inductor.
Phasing network at the base of the tower.
Ground plane:     120 buried radials, 190 m long.

This tower was dismanteled on Aug. 20, 2014.

Main antenna simulation.

West view of the main antenna
West view of the main antenna, Jul. 2002.
North view of the main antenna
North view of the main antenna, Jul. 2002.
Main antenna, viewed from the base
Main antenna, viewed from the base, Jul. 2002.
Close-up on the top radiator
Close-up on the top radiator, Jul. 2002.
Phasing box and feed system
Phasing box and feed system, Jul. 2002.
View of both MW antennas (main and spare)
View of both MW antennas (main and spare), Jul. 2002.

This tower was demolished on Aug. 20, 2014. Here are a few pictures and a video of this event.

Main antenna, Aug. 20, 2014 - 14:00.
Main antenna, Aug. 20, 2014 - 14:00.
Main antenna, Aug. 20, 2014 - 14:05.
Main antenna, Aug. 20, 2014 - 14:05
Watch a movie showing the main antenna demolition (click to download)
Watch the movie of the demolition:
sottens-mw1b.mp4 ( bytes, 27 s, H264, 854 × 480, 24 fps).
Main antenna on the ground, Aug. 20, 2014. Main antenna on the ground, Aug. 20, 2014.
Main antenna on the ground, Aug. 20, 2014.
Main antenna on the ground, Aug. 20, 2014. Main antenna on the ground, Aug. 20, 2014.

Spare medium-wave antenna

Tower type:     125 m self supporting tower.
Antenna type:     Short vertical antenna, isolated from ground.
Feed point:     Inside the tower, at about 40 m.

Even if the transmitter was switched off in December 2010, the tower still exists (Oct. 2014).

Spare antenna simulation.

West view of the spare antenna
West view of the spare antenna, Jul. 2002.
South view of the spare antenna
South view of the spare antenna, Jul. 2002.
Match box and feeder
Match box and feeder, Jul. 2002.
Feeder and feed point
Feeder and feed point, Jul. 2002.
Spare antenna, viewed from the base
Spare antenna, viewed from the base, Jul. 2002.

Short-wave transmitter data

Location:     E 6° 43' 51.53" / N 46° 39' 42.03"
Frequency:     Transmitter is off and dismantled.
Power:     Transmitter is off and dismantled (used to be 500 kW).

Brief history

The Sottens short-waves transmitter started broadcasting on in 1972 with a power of 500 kW and a rotating courting antenna on 9, 11, 15, 17 and 21 MHz bands. It was switched off on October 23rd, 2004. The transmitter and the antenna were dismantled in February 2005. This was the last Swiss shortwave transmitter.


Short-wave antenna

Tower type:     62 m high rotating double curtain antenna.
Antenna type:     2 arrays of 8 dipoles (for two different bands).
Feed point:     With balanced feed lines and transmission line impedance transformers.

The main features of double AEG/Telefunken HR4/4/0.9 antenna are summarized below:

Frequency band: Elevation angle: Half power beam-width: Antenna gain:
Vertical Horizontal
9.5 MHz
11.8 MHz
15.45 MHz
11°

12°
11°
38°
30°
24°
16.2 dBd
17.3 dBd
18.1 dBd
15.1 MHz
17.8 MHz
21.75 MHz
10.6°
9.2°
7.4°
11°
10°
8.5°
36°
31°
26°
16.5 dBd
17.3 dBd
18.0 dBd

This antenna was dismantled in February 2005.

West view of the SW antenna
West view of the SW antenna, Jul. 2002.
East view of the SW antenna
East view of the SW antenna, Jul. 2002.

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