Example of Grounding for Radio Reception.
It is not widely known, but connecting the radio set to the ground significantly increases the reception level and quality. Before assuming that a radio is faulty, it is important to check its proper grounding. The Antenna and Ground terminals are accessible at the back of the radio set. If there are mains outlets equipped with a ground terminal, it can be connected to the radio. Otherwise, attach an electrical wire to a copper pipe.
The figure below shows the back panel of a Philips 521A (1933).
Until the 1960s, grounding was often neglected in electrical installations. As a result, technical literature featured diagrams like the one above, where the ground connection was made using a metal plate or wire mesh placed on a layer of coke (note: coke, not charcoal) buried 1 meter underground and regularly watered (in summer). An interesting article on setting up a «proper» ground for amateur radio can be found in the site's summary.
