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  • 8/8/2010

The Day in History:

Collapse of Warsaw Radio Mast (1991)

radio station

The Warsaw Radio Mast or Warszawa Radio Mast was the world's tallest structure until its collapse on 8 August 1991.

Warsaw Radio Mast, which was designed by Jan Polak, was 646.38 metres (2,120.67 ft) tall. Its construction started in July 1970, and was completed on 18 May 1974, and the transmitter that used it entered regular service on 22 July of the same year. It was located in Konstantyn?w, G?bin, Poland, and was used by Warsaw Radio-Television (Centrum Radiowo-Telewizyjne) for longwave radio broadcasting on a frequency of 227 kHz (before 1 February 1988) and 225 kHz (after). Because a voltage potential of 120 kV existed between the mast and ground, it stood on a 2 metre high insulator. It operated as a mast radiator, so its height was chosen in order to function as a half-wavelength antenna at its broadcasting frequency. The signals from its 2 megawatt transmitters could be received across all of Europe, North Africa and even in North America. Its weight is debated: 380 tonnes, 420 tonnes, 550 tonnes and even 660 tonnes have been cited, probably the result of inaccurate conversion of units by translators. Polish sources claim 420 metric tonnes.

 

Construction

Description of the Gabin transmitter and Warsaw Radio Mast in Polish

The Warsaw radio mast was a guyed steel lattice mast of equilateral triangular cross section, with a face width of 4.8 m. The vertical steel tubes forming the vertices of the mast had a diameter of 245 millimetres; the thickness of the walls of these tubes varied between 8 and 34 millimetres depending on height. The mast consisted of 86 elements, each of which had a length of 7.5 metres. The mast had 3 arrays of guy wires, each attached to the mast at 5 levels. Each guy was fixed on a separate anchor block at the ground and was 50 mm in diameter. In order that the guy wires not interfere with the radio transmissions, the guys were insulated at regular intervals. The weight of guys and insulators used for anchoring the mast was 80 metric tons. An elevator and separate protected ladders were installed in the interior of the mast to facilitate access to the various mast components, including the aircraft warning lamps. The elevator had a maximum speed of 0.35 m/s and required 30 minutes for a trip from the bottom of the structure to the top.

In the lower half of the mast, there was a vertical steel tube, attached to the mast's outer structure with large insulators.

This tube was grounded at the bottom, and connected electrically to the mast structure at half the total height. This technique works by applying a DC ground at a point of minimum radiofrequency voltage, conducting static charge to ground without diminishing the radio energy. Static electrical charge can build up to high values, even at times of no thunderstorm activity, when such tall structures are insulated from ground. Use of this technique provides a certain amount of lightning protection.

A special overhead radio frequency transmission line was used to transfer the signal from the transmitter building to the mast. The transmitter building had a volume of 17,000 cubic metres and was approximately 600 metres from the mast. The transmitter consisted of two 1000 kilowatt units built by Brown Boveri and Cie. An atomic clock was used to generate the transmission frequency in order to provide a very accurate, stable signal source which could be used as a frequency standard by anyone within signal range. The station, which had an area of 65 hectares, also contained a 76 metre tall lattice tower of rectangular cross-section. This tower was used to provide a radio link for programme feeds from the studio.

To supply power to the station a 110kV substation was built. The substation was over-engineered due to the strategic importance of the station as Poland's central transmitter.

Although the power consumption of the transmitting station was large (estimated 6000 kW), the substation was capable of supplying much more than was required.

Small towers were erected around the periphery of the station's grounds in order to support aircraft warning lamps where the guy ropes were located. For photo see:

The official name of the facility was Radiofoniczny O?rodek Nadawczy w Konstantynowie (Radiophonic Transmission Center Konstantynow), Radiowe Centrum Nadawcze w Konstantynowie (Radio Transmission Center Konstantynow) or Warszawska Radiostacja Centralna (WRC) w G?binie (Warsaw Central Radio Station Gabin). The radio program was called "Program Pierwszy Polskiego Radia" (The 1st Program of Polish Radio) "Program I PR" or unofficially "Jedynka" (The One).

Approximately ten years after completion of the mast, inspections revealed structural damage caused by wind-induced oscillations at the mast, the backstage insulators and the guys. Repair work was very difficult and replacement of the mast by a stronger construction of the same height was considered. However, this was not realized, as a result of Poland's economic situation. In 1988 the mast was repainted, but this could not be done to the desired extent, as there was not enough paint available.

CollapseOn 8 August 1991 at 16:00 GMT the mast collapsed due to an error in exchanging the guys on the highest stock of the mast. The mast first bent and then snapped at roughly half its height. A small mobile crane, property of Mostostal Zabrze, was destroyed in the collapse. The helix building and the transmitter building (including the transmitter devices in it) were not damaged.

An investigating committee determined that blame lay with Mostostal Zabrze, which built and maintained the mast. The construction coordinator and the chief of the Mostostal division that built the mast were accused of causing the collapse. The former was sentenced to 2.5 years, the latter to 2 years.

Since the time of the collapse of the Warsaw radio mast, the tallest structure in Poland has been the transmission mast for FM radio and TV at Olsztyn-Pieczewo with a height of 360 metres (coordinates: 53°45?13?N, 20°30?57?E).

After the collapse, the KVLY-TV mast outside Fargo, North Dakota, USA, regained its title as the world's tallest structure, standing 628.8 m (2,063 feet).

radio station

Replacement

After the collapse of the radio mast at Konstantyn?w, the Polish broadcasting company used the old transmitter of Raszyn with its 335 metre high mast near Warsaw, which had been used since 1978 during the day for the transmission of a second programme of the Polish broadcasting service in the longwave range on the frequency 198 kHz, for transmissions on 225 kHz with a power of 500 kilowatts. It is not possible to transmit from Raszyn on 198 kHz and 225 kHz simultaneously, so the transmissions on the second long wave frequency 198 kHz had to be discontinued until either a second long wave broadcasting transmitting facility was built in Poland or a special frequency switch, which would allow transmissions on both frequencies, was installed at the Raszyn transmitter. The latter, simpler solution would have decreased the effectiveness and reliability of both transmitters and was therefore found unacceptable.

Because the Polish long wave transmitters are of special importance to Polish people abroad, as early as April 1992 the Polish government planned to rebuild the mast at Konstantyn?w. In September 1995 the Polish government was set to rebuild the mast. Although refurbishment of the old basements, which could be reused, had already started, the rebuilding of the mast had to be cancelled due to protests of people living in the surrounding area, who claimed that radiation from the mast was a health hazard. While the accuracy of these claims has not been verified, a new site for the transmitter was sought. One was found in the form of an old military area just southeast of Solec Kujawski, where from 1998 to 1999 a new longwave transmission facility was built with a transmitter of 1200 kW output power for the frequency 225 kHz. This facility, which was inaugurated on September 4, 1999, uses as aerials two grounded, upfeed masts, which are 289 metres tall and 330 metres apart.

After the inauguration of the transmitter at Solec Kujawski, the transmitter at Raszyn was again used for transmitting on the frequency 198 kHz for the programme Radio Parliament.

Current state of site

Except for the mast and the radio frequency transmission line that led to it, nearly all components of the facility remain in place, unused and slowly deteriorating.

From the mast itself, the basement, the anchor blocks and the hole in the ground, at which the insulated mounted steel tube in the mast ended, are still there. See photo here.

There are several plans to transform the former transmitter building into a technical museum. In spite of the great historic importance of the site, there is no support for this idea from officials.

In popular cultureThe Warsaw radio mast was mentioned in Guinness World Records as the world's tallest structure. It was also shown on local postage stamps.

TriviaThe mast was unique in the following aspects:

As opposed to radio masts in the USA of similar height, such as the KVLY-TV mast at Blanchard, North Dakota, which simply support FM and TV transmitting antennas, the Warsaw Radio Mast was itself a radiator, insulated from ground. In the entire Western hemisphere, no ungrounded structure of comparable height has ever been erected. The tallest ungrounded structures in the Western hemisphere, the two masts of VLF transmitter Lualualei are, at 458 metres, considerably shorter than the former Warsaw Radio Mast.

There was never an architectural structure of comparable height in Europe outside the territory of the former Soviet Union. The second tallest structure ever built in Europe outside that area, the longwave radio mast in Hellissandur, Iceland, is 412 metres. Even Ostankino Tower in Moscow, Europe's tallest free-standing structure, was surpassed by this mast by more than 100 metres.

It was the only half wave radiator for longwave ever constructed.

Until 2004, when work began on Burj Dubai, no construction of a taller architectural structure was ever initiated.

Replicas

Eldorado Do Sul RBS Radio Mast, a mast radiator in Eldorado Do Sul, Brazil is a nearly perfect replica of Warsaw Radio Mast with 35.5 % of its height.

Source: encyclopedia.thefreedictionary.com


Other Links:

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