||This article may require cleanup to meet Wikipedia's quality standards. The specific problem is: Poorly written, perhaps machine translated. (November 2014) (Learn how and when to remove this template message)|
Longwave frequency 272 kHz was assigned to Czechoslovakia in 1948 (the Copenhagen frequency plan). Before, during the WWII, it was used by German Deutschlandsender. Construction of new transmitter started in 1950 and finished in December 1951. Tests lasted until February 1952. Its power output was 400 kW (2x 200 kW). In the beginning it was transmitting radio programme "Československo 1", later "Hvězda".
Between 1957–1958 Topolná was also used to transmit a Hungarian radio programme on wavelength 49 meters. Between 1953–1960 and again between 1969–1973 one of its masts was used for transmission on frequency 173 kHz. During years 1975–1978 the trasmitter was reconstructed and since November 1978 its transmission power increased to 1500 kW.
On October 1, 1989 the frequency was changed to 270 kHz. After the Velvet Revolution (1989) the transmitted programme was renamed from "Hvězda" to "Radiožurnál". In January 1994 one of the masts was switched off, reducing the output power to 750 kW, to bring down the costs. Further reduction of output power followed in January 2002, to 650 kW. As there were nearly no other transmitters working on the frequency 270 kHz its programme ("ČRo 1 - Radiožurnál") was well received in whole Europe, especially at nighttime.
Since the mid-2000s Czech Radio announced its intention to close down the transmitter several times. In late 2013 it was announced that the broadcasts would cease on February 28, 2014. However the station is reportedly still on air, albeit now at greatly reduced power.
Topolná uses a directional antenna, whose maxima pointed in an East–West direction. By this radiation pattern, it is assured that Topolná transmitter can be received well in all parts of the Czech lands and Slovakia.
For the realization of this directional antenna pattern two 257 metre (835 feet) tall guyed lattice steel masts are used. These masts were, until the mid-1970s, used as ground-fed mast radiators and are therefore insulated against ground. In the mid-1970s the transmission power was increased to 1500 kW, making the Topolná transmitter to one of the most powerful transmitters in Europe. By this measure, both masts were equipped with cage wire antennas, which made their electrical insulation against ground obsolete. After inauguration of these cage antennas the basement insulators were bridged, but remained in place.
As in other high power transmission facilities in Central and Eastern Europe the Topolná transmitter uses special overhead lines for transmitting the RF-power from the transmitter building to the masts.
- 1948 Copenhagen Frequency Plan
- History of tramsitter Topolná (in Czech language)
- "Longwave Czech Radio broadcasting ends on February 28, 2014" (in Czech). Czech Radio. 29 September 2013. Retrieved 21 December 2013.
- Topolná Radio Transmitters at Structurae
- Entry of Mast 1 at Skyscraperpage
- Entry of Mast 2 at Skyscraperpage