Description
The action of this detector is based upon the fact that only the tip of a platinum wire a few thousandths of an inch in diameter is immersed in an electrolyte solution, and a small D.C. voltage bias is applied to the cell thus formed. Platinum is used because other metals are too quickly dissolved in the acid. The resulting bias current decomposes the solution by electrolysis into tiny gas bubbles that cling to the metal point and tend to insulate the metal tip from the solution thus reducing the bias current. An incoming R.F. current can flow better in the direction across the point that makes the point more negative. That recombines the gases and increases point exposure to the liquid. RF current flow in the direction that makes the point more positive only reinforces gaseous blocking of the point. Detection results from this asymmetrical flow.
In practical use a series circuit is made of the detector, headphones, and a battery with a potentiometer. The wire is made positive, and the signal to be demodulated is applied directly to it; a small (about 5 ml) platinum cup filled with either sulfuric or nitric acid completes the headphone circuit, and is also connected to ground to complete the signal circuit. To adjust the cell, the point of the wire electrode is dipped into the electrolyte and the potentiometer adjusted until a hissing noise is heard in the headphones; the potentiometer is then moved back until the noise just ceases, at which point the detector is in its most sensitive state.
It was found that strong atmospheric noise would render it insensitive, requiring that the device be rebiased after each strong burst of static interference.
Read more about this topic: Electrolytic Detector
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