The electrolytic detector, or the bare-point electrolytic detector as it was also called, was a type of wet demodulator used in early radio receivers. This article is about a radio receiver for other uses see Radio (disambiguation. This form of detector was in extensive use, and was very sensitive and reliable. A detector is a device that recovers Information of interest contained in a Modulated wave

History

While working to develop voice transmission, Reginald Fessenden realised that the radio detectors available would not be suitable for his purpose. Reginald Aubrey Fessenden ( October 6, 1866 &ndash July 22, 1932) born in East Bolton, Quebec, Canada, was Although they worked well for receiving the on-off signals of spark gap transmitters, the coherer and related types of detectors were not, in today's terms, fast enough for receiving audio signals. On-off keying ( OOK) is a type of Modulation that represents Digital Data as the presence or absence of a Carrier wave. A spark-gap transmitter is a device for generating Radio frequency electromagnetic waves. coherer was a primitive form of radio signal detector used in the late nineteenth and early twentieth centuries consisting of a capsule of metal filings in the space between An audio frequency (abbreviation AF) or audible frequency is characterized as a periodic vibration whose Frequency is audible to the average human

Fessenden developed what he called a barretter detector that would work to receive AM signals, but it was not very sensitive. The hot wire barretter was a demodulating detector invented in 1902 by Reginald Fessenden that found limited use in early Radio receivers In effect it was Amplitude modulation ( AM) is a technique used in electronic communication most commonly for transmitting information via a Radio Carrier wave The barretter used a fine platinum wire, called Wollaston wire, manufactured as a platinum core in a silver sheath that had to be stripped off with acid. In the process of stripping some Wollaston wire, Fessenden left it immersed in acid too long, until only a tip remained in contact with the solution; he noted that it responded well to radio signals being generated nearby, and could be used as new type of detector.

This story was disputed at the time, with credit for the discovery also given to Michael I. Pupin, W. Mihajlo Idvorski Pupin, PhD LLD ( 4 October, 1858 &ndash 12 March, 1935; Serbian Cyrillic: Михајло Идворски Schloemilch, Hugo Gernsback and others. Hugo Gernsback ( August 16 1884 – August 19 1967) born Hugo Gernsbacher, was a Luxembourg American Inventor However, it is apparent that Fessenden was the first to put the device to practical use.

Description

The Bare-Point Electrolytic Detector

The action of this detector is based upon the fact that if the 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 (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 An electrolyte is any substance containing free Ions that behaves as an electrically conductive medium Direct current ( DC) is the unidirectional flow of Electric charge. Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical 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. Bias is a term used to describe a Tendency or Preference towards a particular perspective, Ideology or result especially when the tendency interferes In chemistry and manufacturing electrolysis is a method of separating chemically bonded elements and compounds by passing an Electric current An incoming R.F. current can flow better in the direction across the point that makes the point more negative. Radio frequency ( RF) is a Frequency or rate of Oscillation within the range of about 3 Hz to 300 GHz Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. 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 gasius 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. If two or more circuit components are connected end to end like a daisy chain it is said they are connected in series. Headphones (also known as earphones, earbuds, stereophones, headsets) are a pair of small Loudspeakers or less commonly a single In electronics a battery is a combination of two or more Electrochemical cells which store chemical Energy which can be converted into electrical energy A potentiometer is a three-terminal Resistor with a sliding contact that forms an adjustable Voltage divider. 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. Sulfuric (or sulphuric acid, H 2 S[[oxygen O]]4 is a strong Mineral acid. Nitric acid ( H[[nitrate NO3]] also known as Aqua fortis and spirit of nitre, is a highly corrosive and 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. Atmospheric electricity is the regular diurnal variations of the Earth 's atmospheric electromagnetic network (or more broadly any Bias is a term used to describe a Tendency or Preference towards a particular perspective, Ideology or result especially when the tendency interferes

Sealed-point detector

Another form of electrolytic detector, the sealed-point electrolytic detector, which could stand considerable rough usage, was commercially known as the Radioson Detector; it had the cell sealed in a glass envelope. The operation was the same as in the bare-point electrolytic detector, the advantage being that the acid was sealed in, and consequently could not spill or evaporate.

External links

• Detectors of electrical oscillations
• Tech Definitions - Radio Concepts
• United States Early Radio History