<P> The tower has been used for making radio transmissions since the beginning of the 20th century . Until the 1950s, sets of aerial wires ran from the cupola to anchors on the Avenue de Suffren and Champ de Mars . These were connected to longwave transmitters in small bunkers . In 1909, a permanent underground radio centre was built near the south pillar, which still exists today . On 20 November 1913, the Paris Observatory, using the Eiffel Tower as an aerial, exchanged wireless signals with the United States Naval Observatory, which used an aerial in Arlington, Virginia . The object of the transmissions was to measure the difference in longitude between Paris and Washington, D.C. Today, radio and digital television signals are transmitted from the Eiffel Tower . </P> <Table> <Tr> <Th> Frequency </Th> <Th> kW </Th> <Th> Service </Th> </Tr> <Tr> <Td> 87.8 MHz </Td> <Td> 10 </Td> <Td> France Inter </Td> </Tr> <Tr> <Td> 89.0 MHz </Td> <Td> 10 </Td> <Td> RFI Paris </Td> </Tr> <Tr> <Td> 89.9 MHz </Td> <Td> 6 </Td> <Td> TSF Jazz </Td> </Tr> <Tr> <Td> 90.4 MHz </Td> <Td> 10 </Td> <Td> Nostalgie </Td> </Tr> <Tr> <Td> 90.9 MHz </Td> <Td> </Td> <Td> Chante France </Td> </Tr> </Table> <Tr> <Th> Frequency </Th> <Th> kW </Th> <Th> Service </Th> </Tr> <Tr> <Td> 87.8 MHz </Td> <Td> 10 </Td> <Td> France Inter </Td> </Tr>

Where did the steel for the eiffel tower come from