When 1 Think Back.. by Neville Williams

Sir John Ambrose Fleming: He invented radio valves - or did he? Dr/Professor Sir John Ambrose Fleming is remembered primarily as the inventor of the Fleming thermionic, and the 'father' of radio valves, which were fundamental to the subsequent development of the industry. Whether or not this is strictly correct is debateable but, either way, Ambrose Fleming made a very considerable contribution to basic electrical and electronic technology.

Curiously, one finds scant mention, in patent rights in respect to the ther- relevant textbooks, of Fleming's per- mionic diode; but more about that later! sonal background or his academic ca- Sir John Ambrose Fleming - a gifted reer. Beyond the fact that he was born Fleming the academic scientist of his day. in 1849, the texts to which I had access Curious about Fleming's academic ca- make little or no reference to his birth- reer, I checked through a number of old I have little doubt that the 'rules-of- place, his family or the steps in his ca- reference books in my possession. thumb' we were invited to memorise in reer which led to his ultimate knight- First off, a brief entry in a 60-year old other days were devised by John Am- hood. Pear's encyclopedia indicated that Flem- brose Fleming, the subject of this pre- The British technical writer/consultant ing's involvement with the University sent article. S. Handel comes closest in The Elec- College spanned 40-odd years, from There is no ambiguity, however, tronic Revolution (Penguin Books, UK, 1885 to 1926, by which time he would about the Dr J.A. Fleming whose work 1967). I quote: have been in his mid '70s. features prominently in another old Next in line was a 1931 copy of the textbook: The Calculation and Measure- At the turn of the century Fleming, Admiralty Handbook. Prompted by the ment of Inductance and Capacity, by then a young professor of electrical engi- index, I re-discovered several long-for- W.H. Nottage of the Marconi Works, neering at University College in London, gotten references to Fleming's left-hand Chelmsford (Wireless Press, London, was appointed scientific adviser to the and right-hand rules, which correlate 1916). Edison Electric Light Company of Lon- current flow, the direction of magnetic Nottage quotes basic research into ca- don and became familiar with Edison's flux and the mechanical force in mag- pacitance by Fleming, as described in lamp experiments. He subsequently be- netic systems (Fig.1). his book The Principles of Electric came a consultant to the British Marconi The 'Fleming' responsible is not iden- Wave Telegraphy, 2nd Edition, page Company which was looking for a better tified by the Admiralty Handbook, but 179. detector of wireless signals than the clumsy and troublesome devices used by Marconi. It so happens that Handel was, him- self, educated at the same University. Clearly, in the 50-odd years between 1849 and the turn of the century, Flem- ing had earned sufficient recognition at an academic and practical level to com- Fig.1: Fleming's mend him as an independent consultant left-hand rule for remembering the to the Edison & Swan Electric Light relationship group and later (in 1889) to the newly between motion, formed British . magnetic field As a consultant, he had ready access and induced to Edison's lamp technology and to voltage. Marconi's pioneering ventures into wire- less telegraphy — involvements that complicated subsequent litigation about

20 Australia, April 1990 A further reference is to adjustable mionic diode appears to be in relatively waveform filters devised by Fleming and low key. A snippet of a letter to Marco- Dyke, to facilitate their investigations ni, in his own handwriting, reproduced into power factor and the conductivity with the above-mentioned Practical of dielectrics. (j.I.E.E. , xlix 1912, Wireless article gives no hint that Flem- p.323). ing's evaluation of the diode extended Again, a method of measuring capaci- beyond his immediate area of concern tance is described, with a low-resistance — a potentially useful method of sensing battery as a DC source. Attributed to signals. It reads: Fleming & Clinton, it used a spinning I have found a method of rectifying commutator to pulse charge the un- electrical oscillations that is making the known, capacitance at a rate of typically Fig.4: The Fleming-Anderson bridge, flow of electricity all in the same direc- 100pps and to pulse discharge it alter- developed to measure inductance. tion, so that I can detect them with an nately at the same rate through a ballis- ordinary mirror galvanometer. tic galvanometer, the readout being in- I have been receiving signals on an terpreted in terms of capacitance. The Fleming-Anderson bridge (Fig.4) aerial with nothing but a galvanometer (Fig.2). provided a means of measuring induct- and my device, but at present only on a ance. According to the text, it could be laboratory scale. used with alternating current input or This opens up a wide field of work, as with direct current in conjunction with a I can now measure exactly the effect of buzzer-interrupter or a make-and-break the . key. It was nulled by adjusting for I have not mentioned this to anyone minumum sound in the phone T, but yet as it may become very useful. could reportedly yield more accurate re- Yours very sincerely, sults with the benefit of measurement J.A. Fleming. methodology described in Watson's Fig.2: Fleming and Clinton devised Practical . Contemporary paper this simple system for measuring If the above is more characteristic of capacitance, using a galvanometer. Fleming & the diode an academic than an enthusiast and a According to Nottage, the method While there is ample evidence as visionary, the same goes for his contem- was detailed in Dr Fleming's books: above of an active and innovative aca- porary paper on the thermionic diode, a Wireless Telegraphist's Pocket Book demic career, the fact remains that most copy of which was made available to me and The Principles of Electric Wave biographical references to Fleming con- some time ago by Mr C.H. Scott of Ip- Telegraphy and Telephony, published at centrate on his rationalisation of the so- the time by Wireless Press, UK. called 'Edison effect' culminating, in (A similar contemporary title by November, 1904, in the almost legend- Fleming, An Elementary Manual of Ra- ary Fleming diode. diotelegraphy and Radiotelephony was For sure, it was an important break- quoted as a reference by Peter Jensen through in its in own right, but to ac- for his article 'Spark: an old-time Induc- claim Fleming's elementary thermionic tion Coil' in the April and June '89 diode as the the original radio valve and issues of this magazine). the genesis of the electronic revolution But back to Nottage: the measure- may be open to question. ment bridge illustrated in Fig.3 is cred- That he was so acclaimed is evidenced ited to Fleming and Dyke and was used by the fact that, in 1927, a landmark by them to measure capacitance or, year for wireless broadcasting, full-page more importantly, in researching power advertisements in popular wireless factor and the conductivity of dielec- magazines for Amplion horn loudspeak- trics. ers carried a personalised product en- dorsement by Dr J.A. Fleming, de- scribed as 'the original inventor of the thermionic valve' (see illustration). More recently, on the 60th anniver- sary of the Fleming diode, the well known English journal Practical Wire- less for January 1965 published a com- memorative article under the heading: 'FLEMING ... AND THE DIODE — 60th Anniversary of the invention of the Thennionic Valve by Sir Ambrose Fleming FRS.' Quite a few writers insist, however, Fig.3: The capacitance measurement that some of the credit allocated to Fleming's first experimental diode bridge attributed to Fleming and Fleming really belongs to others. Again detector valve, developed in 1904. it Dyke, by Nottage. It also measured — more about this later! became the subject of considerable dielectric performance. Fleming's own reaction to the ther- legal argument. ELECTRONICS Australia, April 1990 21 When I Think Back swich, Qld. It comes from Technics, a monthly publication from George Newnes, London, dated April 1905. Contemplating such an innovation, one rather expects a title along the lines of: 'A New and Revolutionary Method of Detecting Wireless Signals'. Instead, we have the bland and predominately academic heading: 'On the Electric Conductivity of a Vacuum' by J.A. Fleming, MA, DSc, FRS. Perhaps wireless communication and a device based on electron emission was The Marconi wireless station at Poldhu, in , UK, pictured in 1901. such a non-issue to readers of Technics Designed by Fleming, it was used for the first trans-Atlantic communication. in 1905 that the notion of an electrically conductive vacuum was judged to be minium plate, in some electrolyte yield- the applied voltages, along with phos- more titillating; that's certainly the way ing oxygen, then a current of positive phorescence and other phenomena to it's presented by the author. electricity can pass from the carbon to do with Crookes and Roentgen tubes. In the paper, Fleming envisages a the aluminium but not in the reverse di- He also makes the point that current glass tube containing two electrically ac- rection. due to the presence of free electrons To explain conduction by an evacu- cessible platinum plates, the whole as- can be drawn off by inserting a carbon sembly being sealed and evacuated to ated thermionic diode, along with a rec- or water-cooled iron probe into the ac- tifying action, Fleming says: one hundred-millionth of an atmos- tive, ionised region of an arc. It is reasonable to suppose, he adds, phere. With a gap between the plates of In any mass of matter, such as a that free electron phenomena even play as little as 1mm, he says, no measurable metal, there must be, in addition to the an integral part in ordinary combustion current flows between them, even with complete atoms or molecules constituting in a coal fire, with 'carbon positive ions' an applied potential difference of the mass, a distribution throughout it of (formed by losing free electrons) exhib- 100,000 volts. free electrons, the percentage of these in- iting an affinity for 'negative oxygen Equally, a spark coil, which might creasing with the temperature. These ions' (having absorbed such electrons) bridge a gap of several centimetres in electrons cannot escape from the mass to promote the creation of electrically air, would produce no evident discharge when cold because if they did they would neutral molecules of carbon dioxide. across the same 1mm in evacuated leave it positively electrified. If on the space. other hand, we electrify the mass nega- The diode detector This would indicate that, in normal tively to a high potential and raise it to a Only towards the end of the 7-page circumstances, a vacuum is an excep- high temperature, electrons can escape paper does he get around to the use of tionally good insulator. freely from it. his diode for detecting wireless telegra- If the plates were to be replaced by Very new concept phy signals. But even then it is in the platinmum or carbon wires, or fila- context of a laboratory experiment ments, exactly the same observation Nowadays, any student of high school physics is aware of the molecular/atomic (Fig.7), consistent with his hand-written would apply — provided the wires re- note to Marconi. For his Technics read- main cold. composition of matter, of sub-atomic ers he explains: particles and of electron emission phe- Current in a vacuum nomena. But in 1905, it was at the lead- We may, for instance, set up an elec- However, continues Fleming, if one ing edge of new and unfamiliar tech- tric oscillation by the discharge of a con- of the wires is heated in the manner of nology, being expounded as such by denser in one circuit. Then, at a distance a lamp filament by connecting it to a eminent physicists like Ambrose Flem- of several feet or several yards, we may suitably insulated battery, a discharge of ing. set up another- circuit including a galva- current may occur between the wires In the process, he was already con- nometer and a , and we across the intervening evacuated space. fronted with the apparent conflict be- may produce a deflection in the galva- It transpires that such current flows tween electron flow (negative to posi- nometer showing it is transversed by a only when the incandescent filament is tive) and the purely arbitrary conven- continuous current when we set up an negative with respect to the one which tion that electricity flowed from positive alternating current in the primary cir- is not artificially heated. If an alternator to negative. In his explanatory diagram cuit. is connected between the two filaments, for a diode (Fig.5) he adopts the verbal Such an arrangement, he adds, can be in series with a galvanometer, the latter device of a flow of 'negative electricity'. used as a receiver for wireless signals, at will register a steady reading due to the Another diagram in his paper (Fig.6) the same time conceding that "it is not flow of a unidirectional current. emphasises that conduction through a so sensitive as the or the mag- Fleming points out that the rectifying diode does not obey Ohm's Law, netic detector". effect is broadly similar to that of the behaving quite differently from a resis- Even so, Fleming explains, "the gal- Nodon valve', an electrolytic (`slop') tive circuit. vanometer will give a steady deflection rectifier that would be familiar to his At this stage, the author diverges into all the time that electric waves are fall- readers. I quote: a broad discussion of electron emission ing on the wire, and if the galvanometer It is well known that, if a carbon or effects, including the influence of the is that kind of instrument called 'a iron plate is placed, together with an alu- degree of evacuation and the order of speaking galvanometer' it will give de-

22 ELECTRONICS Australia, April 1990 Current 5 .z 8 z (Jo C.) U \ Co QC/41, •

VOLTAGE

Figs.5 and 6 (above left, right): Diagrams from Fleming's 1905 paper explaining diode operation. Fig.7 (far right): From the same paper, his diagram showing the use of the diode as a detector for wireless signals. Note the lack of any tuning arrangement. flections larger or smaller in proportion and Walter Welch had occasion to look tific body. Sir William passed one or as the wave trains falling upon the fairly critically at the history of the ther- more of them on to Professor Fleming, aerial are longer or shorter. In this mionic diode; this as background to the describing them, possibly for the first manner, signals in accordance with the evolution of thermionic valves generally time, as 'Edison Effect' tubes. Morse Code alphabet may be rendered and to electronic disc recording and Taking advantage of his association visible by the deflections of the galva- playback. with Edison & Swan, Fleming had a nometer." John W. Stokes did similar research number of similar tubes made up for (Fleming notes in the following para- for his book 70 Years of Radio Tubes himself. Having verified Edison's and graph that speaking galvanometers were and Valves (Vestal Press, N.Y. 1982) Howell's findings, he put them away in currently being used for undersea cable and what follows draws on their find- a laboratory cupboard, where they still telegraphy). ings. were in 1897 when J.J. Thompson came In evaluating Fleming's apparently They agree that in 1883, Thomas A. up with his electron theory. low-key attitude to his thermionic detec- Edison realised that charged particles of In the light of this new concept, and tor, the present day reader needs to some sort were being emitted from the aware of Marconi's need for a more realise that, in 1905, the role of a 'de- incandescent carbon filament in evacu- reliable detector, Fleming decided to tector' was to indicate audibly or visu- ated lamps. His observations were docu- check out his 'Edison Effect' rectifier ally the presence of bursts of unmodu- mented by Prof. Edwin J. Houston and tubes in that role. They had their limita- lated or randomly modulated arc- became the first paper to be published tions, but worked well enough to justify sourced wireless energy, sufficient for by the AIEE (American Institute of application for a patent, on the basis of them to be recognisable as Morse Code. Electrical Engineers). their use with different external circuitry While Fleming saw his diode as new In the following year (October 1884) for a totally different purpose: the de- and potentially useful, he also admitted Edison took out a patent, which cov- tection of high frequency wireless that it was less sensitive than other cur- ered the idea of intercepting the parti- waves. rently available devices — a crucial con- cles with a metallic plate placed within A patent was duly granted in Novem- sideration prior to the introduction of the evacuated envelope and using the ber 1904 and, under the terms of his receivers using valve type signal ampli- resultant current as a method of moni- contract, was assigned to the Marconi fiers. toring the line voltage. The patent had Company, with no pecuniary reward to Wireless telephony was also in its in- no real practical value for Edison, but Fleming other than his regular retainer fancy and the consequent role of a de- was taken out as a purely precautionary as a consultant. tector as a demodulator of incoming cover. On the strength of the patent, the amplitude modulated speech and music Nevertheless, this discovery, paper Marconi Company began manufacturing signals was not widely appreciated — and patent, according to Read and thermionic in 1907, mostly with perchance even by Fleming in 1905. Welch, provide the real starting point 4-volt filaments, plate connections on In this connection, Marconi was said for what is now known as 'electronics'; the side of the bulb and, ironically, Edi- to have been singularly uninterested in this in 1883/4. son-lamp type bayonet or medium screw speech communication. His commercial While experimenting with one of the bases. objective was to establish reliable long- tubes, John W. Howell, an associate of distance communication using brute- Edison in the Harrison laboratory, dis- US Federal Court force, arc-based wireless telegraphy, covered that it could also be used as a The tenuous nature of the rather than getting involved in the con- rectifier. This, too, was written up in Fleming/Marconi patent came under siderable complications of voice trans- the AIEE Transactions , but was ignored scrutiny some time later, when the Mar- mission. His attitude would undoubtedly on principle by Edison — a fanatical DC coni Company took action against Lee have had a bearing on Fleming's out- man who would have nothing to do with de Forest in the Federal Court for the look as a consultant to British Marconi. AC mains, or rectifiers! Southern District of New York, claim- In 1885, Edison gave several of the ing that his American-built equipment Diode origins tubes to Sir William Preece (Chief of using thermionic diodes and For their book From Tin Foil to Engineering, British Post Office) who (modified diodes) breached their 1904 Stereo — Evolution of the Phonograph had arranged the first demonstration of patent. (Howard Sams Inc., 1976) Oliver Read the phonograph in England to a scien- By way of defence, it was put to the

ELECTRONICS Australia, April 1990 23 Wehnelt in January 1904, the reader is Limited to a simple zero-gain receiver When I Think Back left to judge for himself whether Fleming and without the benefit of directional court that the original Edison patent was justified in claiming to have invented aerials, he knew that his only chance of (1884) had clear precedence and that it the world's first thermionic valve. success was to provide a uniquely had lapsed by the passage of time. Mar- Personally, I am in two minds as to powerful signal from the selected trans- coni/Fleming countered with a dis- whether the problem lies in what Flem- mitting site atop a 37-metre (120ft) claimer indicating that their patent re- ing actually believed and claimed, or granite cliff at Poldhu, on the south- lated uniquely to high frequencies, as in what history has thrust upon him. west coast of Cornwall in the UK. wireless telegraphy. To a long-time academic and a Fellow To feed the 70m (200ft) inverted cone De Forest also claimed that his of Royal Society, the Edison Effect was antenna, Marconi reckoned that he operated in the manner of a relay, with a phenomenon that needed to be re- would need a transmitter input power of the grid controlling the amount of solved and written into scientific litera- around 25kW and an HT voltage of energy being drawn from a supplemen- ture. Under commercial pressure from around 20kV, bridging a 50mm (2") tary or 'B' supply. Marconi, however, he may well have spark gap to excite the resonant 'oscilla- This led to a lengthy examination by taken the further step of applying for a tion coils' to which the antenna was the court of other types of wireless de- patent, which might never have been coupled. tector, and claims that a supplementary granted if Edison (or Wehnelt?) had The design of a transmitter to satisfy voltage had been used before to im- seen fit to oppose it. these unheard-of criteria was entrusted prove their performance (as in the co- Morgan E. McMahon (Vintage to an independant consultant — none herer) — thereby anticipating de For- Radio , 2nd Edition, 1973) is supported other than Professor J. Ambrose Flem- est's patent. by John Stokes in adding that Fleming's ing. A photograph in the Marconi Com- In the end, and in some degree be- patent had an unusual personal aspect: pany archives reveals the installation as cause Edison was not a party to the ac- a victim of impaired hearing, he had a major undertaking, bedecked with tion, the Fleming/Marconi patent was difficulty in coping with the wireless sig- `DANGER' and 'STAND CLEAR' no- allowed to stand. nals which he encountered by reason of tices. But it worked. There was much more to it, which I his association with the Marconi Com- Success came at 12.30pm on Decem- shrink from trying to include here, but pany. Because of this, he was especially ber 12, 1901. In Marconi's words: the summation by Read and Welch interested in the rectifying action of the Unmistakably the three little clicks cor- reads as follows: Edison Effect diode and gratified to responding to three dots sounded in my There is revealed a great disparity in find that telegraphy signals could be ear; but I could not be satisfied without the philosophy and reasoning of patent rendered both visible and measurable collaboration. "Can you hear anything, reviewers and of the courts in dealing by using it in conjunction with a galva- Mr Kemp?", I said, handing the tele- with the relative merits of basic inven- nometer (Fig.7). phone to my assistant. Mr Kemp heard tions and of contributory inventions Indications are that, as an inventor, the same thing as I... and/or new uses. de Forest's expectations for his 1906 Those words have been reproduced In this case, although careful distinc- tube were much broader and in- tions were made between the relative countless times in articles and text- dustry-based. Morgan McMahon rates books, more often than not without any claims of de Forest and Fleming, historic his triode as 'the most important discov- justice was denied Edison, whose re- thought of the man who was primarily ery in radio'. responsible for the transmitter which search and accomplishment was so De Forest's triode opened the way to unique in this particular instance that radiated the signals in the first place. RF and audio , and to receiv- Fittingly, in his biography of Gu- the contributions of both Fleming and de ers more sensitive than anyone had ever Forest are quite secondary. glielmo Marconi, David Gunstan refers dreamed of; to vastly improved trans- to a granite column erected on the cliffs Considered from this viewpoint, which mitters, to radio telephony, sound was tacitly admitted by the court, the near Poldhu. On the column is a bronze broadcasting and a world of valve-based plaque which carries the words: contribution of de Forest towards the electronics that reached its peak in the new use in adding the all-important '60s. One hundred yards North East of this third element, was the greater of the column stood from 1900 to 1933 the fa- latter two. Trans-Atlantic wireless mous Poldhu wireless station, designed Amongst others, this last observation If the foregoing observations appear by John Ambrose Fleming and erected is supported by E. George Griffith of to diminish Fleming's contribution by by the Marconi Company of London, Pennsylvania State University, in his way of the thermionic diode, his role in from which were transmitted the first book Basic Electronic Devices (Rine- another wireless 'first' is recounted by signals ever conveyed across the Atlantic hart Press, San Francisco, 1971). I way of compensation. by wireless telegraphy. quote: In the late 1890s, some five years be- One may well quibble about the gene- When introduced a fore the diode patent, Marconi was sis and the hentage of the Fleming third electrode between the cathode and seized with the idea of bridging the At- diode, but it is difficult not to respect a plate of the diode, he started the vast lantic by wireless telegraphy — an ambi- scientist/engineer able to project a sig- electronics industry that exists today. tion that many ridiculed, on the grounds nal from Poldhu to Newfoundland using that wireless waves could not possibly the hazardous, primitive technology of (70 Years of Radio John Stokes follow the curvature of the earth. Mar- 1901. Tubes & Valves) records the above se- coni thought otherwise and, without Sir Ambrose Fleming died in his 96th quence of events, but leaves the reader knowing anything of ionospheric propa- year on April 18, 1945 at Sidmouth, to ponder a quite different footnote gation, was willing to back his intuition UK, where he had spent in retirement which reads: with his reputation and £50,000 of com- the last few years of an intensely active In view of an earlier patent by A. pany funds. life. 24 ELECTRONICS Australia, April 1990