Long-wave telegraph transmitter Tesla DTV 80 + tuning coils

This is a long-wave telegraph transmitter with 80 kW output power, tunable from 40 to 120 kHz. This frequency enables transmission to very remote places in every hour of the day and in any season of the year. The transmitter was very large, here you can see approx. one sixth of the entire transmitter - the driver stage. A tuning coil and a power supply transformer can also be seen in our museum. The transmitter was originally placed in Poděbrady and was used to send messages to diplomatic missions etc.. It has been withdrawn in the nineties.

The drawback of the long waves is that very powerful transmitters and giant antennas are required to transmit them. The communication was unidirectional, because the same transmitter would be needed to send a message back. The solution is to use short waves which enable connection across the entire globe even with small power and antenna. On the other hand, the connection is not stable and a proper frequency must be selected depending on the condition of the atmosphere, the day time, solar activity etc.

Tuning coils for the DTV 80: The inductance of the movable coil adds or subtracts to the inductance of the fixed coil, depending on the angle of rotation. This is used to exactly tune the driver stage to the output stage on the desired frequency. You can see high-voltage capacitors under the coils. They could be connected to the coils with switches. Tuning the transmitter to a certain frequency was a lengthy and complicated process.