Here is an example of a transmitter that uses no transistors or vacuum tubes. It has only coils of wire, capacitors, a battery, switches and a rotary spark gap. This technology was invented and used by Tesla in the 1880s, not Marconi, although Marconi (history's first "Ham Radio" operator) used Tesla's invention to make the earliest two way radio communication. Tesla is credited with inventing radio.
Tesla's rotary spark gap was used in his famous Colorado Springs experiments, and was later used in the first linear accelerator at the University of California at Berkeley.
This technology is now illegal due to it's wide bandwidth which interferes with other radio communications.