Microphone-Coherer: Extraordinary

The carbon microphone, the first wireless detector – was debunked by the Royal Society – no less

Note: any reference to radio or wireless on this page refers to Morse code transmissions and not audio (speech) transmissions unless otherwise stated.

David Edward Hughes

The microphone is a technology so prevalent in our culture that few of us ever give it a second thought. Microphones are essential for the operation of telephones, mobiles, hearing aids, public address systems for concert halls and public events, motion pictures, live and recorded audio, other audio sound recording, two-way radios, megaphones, radio and television broadcasting, in computers for recording voice and for speech recognition, VoIP, and for non-acoustic purposes such as ultrasonic sensors. It’s something that never occurred to me before I started researching the mic, but without it none of the above technology would be possible. It was Hughes (above) who found that a carbon microphone could be used to detect radio waves and it was he who made the first transmission and reception of a wireless signal.

The Carbon Button Microphone

An early telephone with carbon mic of the type used in the Bell system

The Early Telephone – Alexander Graham Bell
Wiki: Alexander Graham Bell (1847 – 1922) was a Scottish-born scientist, inventor, engineer, and innovator who is credited with patenting the first practical telephone and founding the American Telephone and Telegraph Company (AT&T) in 1885. https://en.wikipedia.org/wiki/Alexander_Graham_Bell

Bell was a teacher of the deaf, not an academic scientist nor was he a qualified engineer. Wiki thinks that using the imagination is equal to scientific qualification when it suits the purpose.

moah.org: While working on devices to help the hearing-impaired in 1876, Alexander Graham Bell developed a simple combination receiver (earphone) and transmitter (microphone) using a bar magnet, a coil of fine wire and a thin metal disk (diaphragm). Bell’s device worked both as a microphone and an earphone….  Unfortunately, the sound was quite weak and could not serve as the basis of a commercial telephone. However, the receiver portion of his device worked very well and was used in virtually all commercial telephones around the world.

The missing element was a better transmitter or microphone. A device that would generate a strong electrical equivalent of the voice would complete a telephone that could be used for long distance communication. This device, the carbon microphone, was invented by both Edison and Francis Blake in 1877 and patented by Edison. It is still in use in many phones today. http://www.moah.org/talkingwires/talkingwires.html?KeepThis=true

The identity of the inventor is still a cause for much controversy…

carbon_buttonEmile Berliner was credited with inventing the carbon-button microphone patented by him on the 16-12-1879. Alexander Graham Bell was so impressed with the carbon-button microphone that he bought the rights for $50,000 (1.1 million dollars in today’s money), so he could use it in his telephone prototypes.

Microphone Wars

Berliner called his microphone a “loose-contact transmitter” because it was composed of two electrical contacts separated by a thin layer of carbon. Thomas Edison claimed that the patent should be his and a legal challenge ensued that ruled in Edison’s favour. In fact neither of them could claim credit as the ‘carbon button mic’ had been know and demonstrated for some time before either claimed it.

Carbon Button Microphone Amplifier http://onetuberadio.com/2017/03/20/carbon-button-microphone-amplifier/

1927 Carbon Microphone is an amplifier

Wiki: Carbon microphones can be used as amplifiers. This capability was used in early telephone repeaters, making long distance phone calls possible in the era before vacuum tube amplifiers. In these repeaters, a magnetic telephone receiver (an electrical-to-mechanical transducer) was mechanically coupled to a carbon microphone. Because a carbon microphone works by varying a current passed through it, instead of generating a signal voltage as with most other microphone types, this arrangement could be used to boost weak signals and send them down the line. These amplifiers were mostly abandoned with the development of vacuum tubes, which offered higher gain and better sound quality. Even after vacuum tubes were in common use, carbon amplifiers continued to be used during the 1930s in portable audio equipment such as hearing aids. The Western Electric 65A carbon amplifier was 1.2″ in diameter and 0.4″ high and weighed less than 1.4 ounces. Such carbon amplifiers did not require the heavy bulky batteries and power supplies used by vacuum tube amplifiers. By the 1950s, carbon amplifiers for hearing aids had been replaced by miniature vacuum tubes (only to be shortly replaced by transistors). However, carbon amplifiers are still being produced and sold.

David Edward Hughes

The microphone is also a coherer (wireless detector)

Carbon pieces in a glass tube initially used in D E Hughes’ microphone, he also used it as a radio frequency detector (coherer) in his wireless experiments.

In 1879 David Hughes, like many others, was experimenting using a Bell telephone (that had a carbon button mic) He found that although there was no connection between the two it was reacting to another piece of equipment that was sparking. He was listening to the sparks via radio waves, or wireless as it came to be known. Hughes seems to have come across the phenomenon of radio waves nine years before they were proven to exist by Heinrich Hertz in 1888.
See also:

Another Hughes Carbon Microphone – mounted on a sounding board

Anyone with a smattering of radio knowledge will know that radio frequency signals cannot be heard through an electromagnetic (dynamic) earphone or speaker alone. It’s a type of earphone and loud-speaker used up-until the present day. All that is heard is a hum, but here was Hughes listening to sparks. A coherer (See below) was normally required to make the sound audible. It transpired that Hughes was listening through a Bell telephone that had a carbon microphone and an electromagnetic earphone. The carbon mic’ was acting as if it were a coherer although such things were not understood at the time.

Hughes carbon microphone

Hughes built a clockwork driven spark transmitter and a modified version of his Bell telephone microphone built into a portable receiver, in order to continue his experiments. He would leave his transmitter running some Morse code-like sounds and walk around London with his portable receiver – the first radio transmissions. He may even have been one of the cell  phone time travelers photographed in 1879 and reproduced on YouTube? Time Travel? Woman Talking on Cell Phone in Charlie Chaplin Movie

Hughes clockwork spark transmitter

royal_societyThe Royal Society waves-away pre-hertzian radio wave detection

Wiki: On February 20, 1880 he (Hughes) demonstrated his technology to representatives of the Royal Society including Thomas Henry Huxley, Sir George Gabriel Stokes, and William Spottiswoode, then president of the Society. Stokes was convinced the phenomenon Hughes was demonstrating was merely electromagnetic induction, not a type of transmission through the air.

Hughes was not a physicist and seems to have accepted Stokes observations and did not pursue the experiments any further. A connection with Hughes phenomenon and radio waves seems to show up 4 years after Heinrich Hertz’s 1888 proof of their existence when Sir William Crookes mentioned in his 1892 Fortnightly Review article on Some Possibilities of Electricity that he had already participated in “wireless telegraphy” by an “identical means” to Hertz, a statement showing Crookes was probably another attendee at Hughes’ demonstration. (There was likely more than one demonstration)

Hughes’ discovery that his devices, based on a loose contact between a carbon rod and two carbon blocks as well as the metallic granules in a microphone that exhibited unusual properties in the presence of sparks generated in a nearby apparatus, may have anticipated later devices known as coherers.
(Note: The phenomenon on which the coherer is based was discovered around the mid 1800’s  by a number of investigators independently prior to Hughes but not for wireless detection – this makes Hughes the discoverer of the wireless coherer.)

Alternate version from Hughes’ notebooks: Mr Spottiswoode, President of the Royal Society, Professor Stokes and Prof Huxley, visited me today at half past three p.m. and remained until quarter to 6 p.m., in order to witness my experiments with the Extra Current Thermopile, etc. The experiments were quite successful, and at first they were astonished at the results, but at 5 p.m. Prof Stokes commenced maintaining that the results were not due to conduction but to induction, and that results were then not so remarkable, as he could imagine rapid changes of electric tension by induction…

Note: Wiki: Sir George Gabriel Stokes, 1st Baronet, PRS 1819 – 1903), was an Irish physicist and mathematician.
Award from the Royal Society: he became a fellow in 1851, he received the Rumford Medal in 1852 in recognition of his inquiries into the wavelength of light, and later, in 1893, the Copley Medal. https://en.wikipedia.org/wiki/Sir_George_Stokes,_1st_Baronet

Electromagnetic induction only works when conductors are in close proximity, like the windings of a transformer. George Stokes should have known better as such things were common knowledge to physicists at the time.
Are we to believe he knew nothing of the work of Michael Faraday FRS  (1791 – 1867)
Two years after the death of Davy, in 1831, he began his great series of experiments in which he discovered electromagnetic induction, recording in his laboratory diary on 28 October 1831 he was; “making many experiments with the great magnet of the Royal Society”.
In 1833, Michael Faraday became the first Fullerian Professor of Chemistry at the Royal Institution of Great Britain, a position to which he was appointed for life without the obligation to deliver lectures.

Back to Hughes’ notebooks
Although I showed several experiments which pointed conclusively to its being conduction, he would not listen, but rather pooh-poohed all the results from that moment. This unpleasant discussion was then kept up by him, the others following suit, until they hardly paid any attention to the experiments, even to the one working through gaspipe in Portland Street to Langham Place on roof. They did not sincerely compliment me at the end on results, seeming all to be very much displeased because I would not give at once my Thermopile to the Royal Society so that others could make their results. I told them that when Prof Hughes made an instrument of research, it was for Prof Hughes’s researches and no one else.

They left very coldly and with none of the enthusiasm with which they commenced the experiments. I am sorry at these results of so much labour but cannot help it. (Geddes, from Hughes’s notebooks) Source: http://blogs.ucl.ac.uk/library-rnid/2013/05/03/the-hughes-microphone-and-a-telephone-for-the-deaf/

Wiki Bias

William Crookes may or may not have been present at the demonstration as inferred by Wiki, but why single him out? Crookes, a major pioneer of particle accelerator physics is unpopular with today’s science due to his involvement in the paranormal. But it was in fact Crookes who brought Hughes’ name to the fore because of his discovery of the first wireless transmissions. In a speech before the Royal Academy in England, Sir William Crookes commented upon electromagnetic waves: “Here is unfolded to us a new and astonishing world, one which is hard to conceive should contain no possibilities of transmitting and receiving intelligence.”

The Royal Society waved-away the discovery of not only the (unknown at the time) coherer detector effect, (crucial to early wireless) but also carbon microphone coherence and delayed the benefits of radio transmissions for a decade. Nothing new there, they do the same thing today. But we have to remember folks, that these were the Royal Society, the  creme de la creme of the scientific dairy – the best that science had to offer… blind to discovery!

Most people get this wrong; the vast majority of scientists do not invent, what they do best is to tell the rest of us what cannot be done (theoretically), just as they did with Hughes; they debunk. My own research shows that most of the important discoveries are by lone individuals like Hughes. It has been admitted by honest scientists that new ideas occur to them rarely if ever. Ironically the reason for this is ‘scientific induction’ – the notion that all ideas are already contained within science and all the scientist has to do is find them. It’s a bit like trying to construct a new word with only a dictionary of known words as a guide, and then being told the new word is already in the dictionary. ‘Everything science does has to correspond with everything science has done’.

Wiki Coherer and faint praise for Hughes

Wiki: In 1879 the Welsh scientist David Edward Hughes found that loose contacts between a carbon rod and two carbon blocks as well as the metallic granules in a microphone he was developing responded to sparks generated in a nearby apparatus. https://en.wikipedia.org/wiki/Coherer#History
The credit for the invention is usually given to Frenchman Edouard Branly. But he only confirmed the the observations made previously by Hughes.

The particle Coherer consists of a tube with two electrodes (P) spaced a few millimeters apart, with loose metal filings in the space between.

We have some comments from ‘Wiki Coherer’
The coherer is doing various different operations here although Wiki has nothing to say about that:

Wiki Coherer History: First use:
The idea that particles could react to electricity was used in English engineer Samuel Alfred Varley’s 1866 lightning bridge, a lightning arrester attached to telegraph lines consisting of a piece of wood with two metal spikes extending into a chamber. The space was filled with powdered carbon that would not allow the low voltage telegraph signals to pass through by but it would conduct and ground a high voltage lightning strike.

Lightening is a spark, bigger but the same as Hughes experiments.

Wiki Coherer Operation:
The basis for the operation of the coherer is that metal particles cohere (cling together) and conduct electricity much better after being subjected to radio frequency electricity. The radio signal from the antenna was applied directly across the coherer’s electrodes. (Some coherers don’t use metal particles)

In the circuit below the coherer seems to be driven (biased) by a low voltage battery.

A Marconi coherer circuit for transmitter and receiver Note the low voltage battery for the coherer circuit.

Definition of a coherer

merriam-webster.com: Coherer: a radio detector in which an imperfectly conducting contact between pieces of conductive material loosely resting against each other is materially improved in conductance by the passage of high-frequency current.
(Again we see that the coherer of choice is the one with metal particles, because other coherers cannot be explained away.)

The coherer changes to low resistivity when there is a high voltage, a radio frequency signal or a low DC voltage applied.

No one has ever adequately explained how the coherer detects (demodulates) a radio signal.


The Marconi magnetic detector needs some explaining  http://www.sparkmuseum.com/MAGGIE.HTM

Some documents – Coherer

Coherersa_review_TOC_Fixed The coherer is a MOM or MIM transistor and, by only a slightly more circuitous route, it appeared as the forerunner to the STM (Scanning Tunneling Microscope).
This one is the most interesting as it suggests other theories and applications of the coherer without the usual pseudo-theorising.

The Coherer This is a video that demonstrates how a coherer works but fails to say why it works. All the demonstrations show that the coherer conducts a DC current when a high frequency current is introduced. They do not explain is how a modulated low frequency audio signal is extracted from a high frequency (radio frequency) signal.

J C Bose’s Wireless Detector patent

Explain how this one works?    http://www.geojohn.org/Radios/MyRadios/Coherer/Coherer.html

In this video from the Edison Tech Center the guy is quite confident that he knows how it all works. But Hughes tells us that he used his carbon microphone (above) and he also used beads of carbon as detectors and so this rules-out a magnetic process as suggested.

This video demonstrates that the Coherer is the elusive Memristor?

Wiki: Memristor Nothing is new, it’s a coherer


A brief history of microphones


Semiconductors – Crystal Detectors and audio reception

Crystal Detectors were found to be more reliable than the coherer but were even more mysterious
The coherer is not a rectifier The crystal detector is a rectifier
Wiki: A crystal detector is an electronic component used to rectify radio frequency alternating current. The “asymmetric conduction” of crystals was discovered in 1874 by Karl Ferdinand Braun, and the first crystal detectors were used to receive radio waves by Braun and Jagadish Chandra Bose in 1894, and improved around 1904 by radio researchers such as Henry H. C. Dunwoody and G. W. Pickard, this device was used as the detector in early crystal radios, from the early twentieth century through World War II, and gave this type of radio receiver its name. Crystal radios were the most popular type of radio until the mid 1920s. The crystal detector was the first type of semiconductor diode, and in fact, one of the first semiconductor electronic devices (after photoconductors).

Wiki: The temperamental, unreliable action of the crystal detector was a barrier to its acceptance as a standard component in commercial radio equipment and was one reason for its rapid replacement by vacuum tubes after 1920. Frederick Seitz, a later semiconductor researcher, wrote: “Such variability, bordering on what seemed the mystical, plagued the early history of crystal detectors and caused many of the vacuum tube experts of a later generation to regard the art of crystal rectification as being close to disreputable.”

Russell Ohl
It seems it was the work of Bell lab’s engineer Russell Ohl in the 1940’s that led to the refinement of crystals that would enable the mass manufacture of stable diodes for wartime radar equipment. A process that was later to be crucial in the development and manufacture of Bell lab’s transistors. See also: https://en.wikipedia.org/wiki/Russell_Ohl

Electrical Engineering Stack Exchange – what does the rectifier do in a crystal radio?
The following website is a question and answer forum and the reader can judge from the answers given that the problem of how a crystal detector works is not going away any time soon: “Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts.
Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top”

Envelope Detector (Crystal Detector)

Wiki,: An envelope detector can be used to demodulate a previously modulated signal by removing all high frequency components of the signal. https://en.wikipedia.org/wiki/Envelope_detector#Demodulation_of_signals

Envelope Follower

We are told that the envelope (in red) is what the crystal detector detects. But it does not exist in any realistic sense – it’s just a drawn red line that ‘represents the modulation of a high frequency signal’. If the high frequency component is removed, as we are told, there is nothing left, nowhere to draw a red line.
Further, what happens when a coherer is used? If there is no rectification as in the crystal detector the red line would be both top and bottom cancelling itself out? So how does this work?

Wartime Foxhole Radio thanks to pinterest.com – no extra detection components here?

After reading the Stack Exchange answers above I recalled many years ago actually doing the experiment myself. I found it is possible to receive audible radio signals with a pair of dynamic headphones, a crystal detector, an antenna and an earth connection – nothing more – no other components. And so I suggest that most of the answers given at Stack Exchange are wrong. We find that Hughes also heard an audible signal with nothing but a carbon mic and a dynamic earphone… no filters.

Wiki’s “…the vacuum tube experts of a later generation to regard the art of crystal rectification as being close to disreputable” They didn’t know how their own vacuum tubes worked, something that persists to this day. See my page: Electron particles
There are theoretical and logical problems…

No one has ever been able to explain how or why the crystal detector works.


Transistors are a development of  crystal detectors

shockley_transistorJohn Bardeen, Walter Brattain and William Shockley

(Bardeen and Brattain’s) final design of a point-contact transistor had two gold contacts lightly touching a germanium crystal that was on a metal plate connected to a voltage source. Also known as the “little plastic triangle,” it became the first working solid-state amplifier.

(They) demonstrated the transistor device to Bell Lab officials Dec. 23, 1947. Shockley was reported to have called it “a magnificent Christmas present.” But Shockley himself was not present when it happened and was said to be bitter over losing out on that day. He had his revenge, though. Shockley continued to work on the idea and refine it. In early 1948, he came up with the bipolar or junction transistor, a superior device that took over from the point-contact type.
Bell Labs publicly announced the first transistor at a press conference in New York on June 30, 1948. https://www.wired.com/2009/12/1223shockley-bardeen-brattain-transistor/

Using improved semiconductor materials developed (by Russel Ohl) for radar detectors during the war, in early 1945 Shockley experimented with a field-effect amplifier, similar in concept to those patented by Heil and Lilienfeld, but it failed to work as he intended.

In 1981 the semiconductor physicist H. E. Stockman said “Lilienfeld (who had a transistor in  1926) demonstrated his remarkable tubeless radio receiver on many occasions, but God help a fellow who at that time threatened the reign of the tube.” See Bell Labs Memorial: ‘Who really invented the transistor?’, starting at “Oscillating Crystals”:

Bell Labs Memorial: Who really invented the Transistor? is here:

Bardeen, Brattain and Shockley had Lilienfeld’s transistor patent to work from.


The Lilienfeld transistor patent 1930

Note the + connection to what seems to be a crack in the crystal. The same thing is noted by Russell Ohl:

The crystal had a crack down the middle. Ohl was examining how much current flowed through one side of the crack versus the other, when he noticed something peculiar. The amount of current changed when the crystal was held over a bowl of water. And a hot soldering iron. And an incandescent lamp on the desk in the room.

By early afternoon, Ohl realized that it was in fact light shining on the crystal that caused this small current to begin trickling through it. On March 6, he showed his prize silicon rod to Mervin Kelly. Kelly quickly called Walter Brattain and Joseph Becker to the scene.

Ohl had his coal-black crystal attached to a voltmeter in front of him. He turned on a flashlight, aimed it at the silicon, and the voltage instantly jumped up to half a volt. This was ten times anything Brattain had ever seen before. He was stunned, but not too stunned to produce an off-the-cuff explanation. The electrical current must be due to some barrier being formed right at the crack in the crystal.

Lilienfeld left clear instructions to Bell lab’s on transistor construction.

Engineer Russel Ohl


Lilienfeld Transistor Radio Circuit


A transistor works in much the same way as a coherer. A coherer is very much like a transistor.

What we have is a history of devices that appear to operate on the loose contact principle, starting with the coherer and culminating with the cracked crystal of Lilienfeld. My own take on these technologies is that they are loose contact micro-sparking devices that change the nature of electricity into exotic forms. This, of course is taboo to the mainstream who’s explanation is a diversion, a shadow that hides the true potential of electronics.


The Free Energy Secrets of
Cold Electricity
Peter A. Lindemann, D.Sc.

For those who think you need to be a physicist to construct a transistor:-

Click-Transistor fabrication: so simple a child can do it

Click- Homebrew NMOS Transistor Step by Step – So Easy Even Jeri Can Do It

Click- Make a Point Contact Transistor at home

See also my page: https://nextexx.com/undeserved-nobel-prizes-transistor/

More to come…


                                                                        The Digging Dog


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