A simple electrochemical cell (a type of element volts) consists of steel and copper plates, separated by a layer blotting paper (15 × 40 mm) impregnated with ordinary tap water or simply saliva (Figure 1a). If the item does not work, it is necessary to soak the paper in a solution of salt (half a teaspoon per cup of water).This "water" supply actuating a device (radio, buzzer, etc.) surprised the uninitiated observer. Bolshy effect makes use of copper, zinc or tin plate. This element consists of a wooden or plastic clothesline clothespins, copper, silver or nickel coin and laying of wet newsprint (Figure 1, b). The electromotive force (emf) Element will be about 0.1 V and can be connected to the battery. Just enter the two conductors - the iron and copper (Figure 1, c) in lemon, apple or pickles (and even better in beer) to get the power supply from the emf 0.1 V. By combining several of these elements will have a battery, suitable for powering the simplest radio.
Power for the radio can draw not only from the antenna, but also a good method of zemli.Eto power radio on trips, camping, camping, etc. If our item placed deep into the ground (deep layer of frost, an average depth of 1 m.), Then they can be used continuously throughout the year.
The construction of "earth" element is shown below. Quality of its operation depends on the type of soil, its humidity, as well as the dimensions and material of the electrodes, a suitable wet greasy soil. The larger the surface electrodes, the smaller the internal resistance of the electric current.Type of material has little effect on the magnitude of the electromotive force source, which usually varies between 0.8 ... 1.1 V.
Best results give the following galvanic couples : zinc-carbon, aluminum - copper, zinc-copper. If the element is connected to any load, its voltage will decrease gradually until it stabilizes after 15 ... 30 min. If there are typical zinc plates (170 x 210 mm) and carbon electrodes from large phone batteries (you can also use carbon rods from 1.5-volt cells), the distance between the electrodes can be 0.3 ... 0.5 m.
Taps from positive performing isolated electrodes with electrodes provodom.Soedinenie performed by welding or soldering. Top Efficiency this element is achieved at a current load of 1 ... 2 mA. (I had reached the current 12 mA, the other principle, but also with the use of the land. Earth battery ).
The figure below shows a diagram of the detector receiver powered earth element, which consists of two round rods - steel (2,5 X 400 mm) and copper (4X400 mm), spaced at a distance of 50 mm. This element works in a mode of 0.5 V / 0.25 mA with dry soil and 0.75 V / 0.9 mA - when wet.
For the satisfactory operation of a simple receiver powered "earth" element, it is necessary to make an outdoor antenna length not less than 4 m and suspend it at a height of not less than 5 m from the ground (the higher the better). If after several months of operation the cell voltage under load is reduced, increase the area of the electrodes. 
"Earth" element and fed them a dual-band receiver.