What type of transmission does Tower to the People and Wardenclyffe Tower have in common?
Wardenclyffe Tower Wardenclyffe Tower (1901–1917), also known as the Tesla Tower, was an early wireless transmission station designed and built by Nikola Tesla in Shoreham, New York in 1901-1902. Tesla intended to transmit messages, telephony and even facsimile images across the Atlantic to England and to ships at sea based on his theories of using the Earth to conduct the signals. His decision to scale up the facility and add his ideas of wireless power transmission to better compete with Guglielmo Marconi's radio based telegraph system was met with the project's primary backer, financier J. P. Morgan, refusing to fund the changes. Additional investment could not be found and the project was abandoned in 1906 and never became operational.
Tunnel transmitter A tunnel transmitter allows wireless reception in tunnels. It consists of a receiving antenna which receives the signal to be radiated in the tunnel, and a transmitting antenna installed in the tunnel, which is either a Yagi antenna or a line antenna. In principle, a tunnel transmitter can work purely passively, in which case the received signal is passed over a cable to the antenna in the tunnel. Active systems, however, are more often used. In some cases the radio frequency inside the tunnel is different from the one used by the broadcaster. More often the program inside is transmitted on the same frequency as outside, in which case the information signal should be demodulated or converted to an intermediate frequency in the outside receiver, and then modulated/shifted back in the transmitter. Otherwise feedback may occur.