First-Hand:A Brief History of the Moorehead Laboratories of San Francisco and its Successor the A-P Radio Laboratories

Submitted by Frank A. Polkinghorn

April 11, 1976

Note: This paper is based entirely upon personal recollections, interviews, and correspondence with several different people, all recorded more than fifty years after the events recalled, and a booklet put out by the Moorehead Laboratories in 1919. No research was made in contemporary newspapers, magazines, or other sources, which undoubtedly could verify and date some of the events mentioned as well as add additional data. Mr. Gunn had in his possession in 1924 a scrap book of clippings about the California Theater station. This has not been located. Incorporation papers filed either in San Francisco or Sacramento would also likely add information. One of the principal persons interviewed declined to accept any credit for the information he supplied on the basis that at his age he did not trust his memory.

Within a few years after the invention of the three-element vacuum tube with a grid interposed between filament and plate by De Forest in 1907 a number of people in New York, San Francisco, and perhaps other places set themselves up to manufacture tubes on a small scale. The impetus for this was the desire to investigate such tubes and/or sell them to ship radio telegraph operators. At that time, on account of patent litigation, the Marconi Company, which effectively controlled the ship-to-shore wireless telegraph business, did not feel free to use vacuum tubes in their receivers but furnished crystal detectors of fair stability but low sensitivity. It became quite common for ship operators to construct vacuum tube receivers and take them aboard ship where they were used in place of the standard equipment and performed vastly better.

About 1913 Mr. Otis B. Moorehead, a ship radio operator whose home was in San Francisco and who is said to have seen tubes made in De Forest's laboratory in New York, set up a small factory in the industrial area south of Mission Street and with the aid of one glass blower started making a simple type of vacuum tube. The envelope was made from a section of 3/4" glass tubing about 4" long. The filament ran through the center of the tube from a stem at one end to a stem at the other end. The plate and grid were concentric with the tube and filament and their leads came out opposite stems. There was no base; leads a few inches long were provided for connecting to binding posts on the receiver.

The original pumping equipment used by Moorehead consisted of one mechanical pump connected to a manifold which accommodated eight tubes. The vacuum he obtained was poor, only a low plate voltage could be used without ionization, and the filament current had to be critically adjusted to get best operation as a detector. These tubes were also used with regenerative feedback to get oscillation so as to receive continuous wave signals.

On account of the patent situation, the tubes were put out without a manufacturer's name and considerable effort was taken to keep the location of the factory secret. The address at which the tubes could be obtained was an uptown real estate office. One man, who wished to obtain some tubes upon which to make some measurements, had considerable difficulty in obtaining the factory address until the real estate operator was convinced that he did not represent a patent owner. The man got some of the tubes and tested them, giving the results to Moorehead, who did not have adequate measuring equipment or knowledge at the time to do the work himself. The Moorehead tubes were marked with "ER" on the plate which stood for "Electron Relay." They sold for about $10.

When World War I started in 1914, the Germans had vacuum tubes and the English wanted to get some. They wrote some specifications and tried to get someone to bid on producing the tubes. The English lamp firms declined to try to meet the stringent specifications and representatives came to the United States where General Electric and Western Electric also are said to have declined to bid. An aggressive promoter who was acquainted with Moorehead's operation learned of the English mission. He knew nothing of the difficulty of meeting the specifications and approached Moorehead, who at first refused to bid, saying he did not know how to meet the specifications. The promoter persisted, promising that he could find the speculative capital with which to build an adequate factory and hire the best talent. After convincing Moorehead that he could handle the situation, the promoter got a contract with the English without letting them get to San Francisco to see the "factory."

The elder Rudolph Spreckles has been mentioned as the one who possibly put up the money to establish the factory, which was set up in a brick building at 638-640 Mission Street on the north side of the street just east of 3rd Street. The company was known as the Moorehead Laboratories. Incandescent lamp making machinery was bought and modified. Oil-immersed, 3-stage mechanical pumps were purchased, and the new Langmuir mercury vapor pumps added to get the highest vacuum possible. Ten pumping stations were built, each with an oven having a manifold for 40 tubes.

The English specifications required that after passing enough current to heat the plate to redness and disconnecting the plate voltage, an inverse voltage of 500 volts should not produce any blue glow which could be seen in a darkened room. The first tubes failed to meet the specifications and even a very long pumping cycle did not produce a satisfactory vacuum.

The lamp industry had earlier experienced difficulty in getting as high a vacuum as desired in incandescent lamps and as a result considerable work had been done toward putting some chemical in the vacuum space with the hope that it would combine with the remaining gases and improve the vacuum. Some library research by a Moorehead engineer at the Mechanics' Institute disclosed an article written by an Italian professor in the early lamp days which stated that he had put some phosphorus on the filament and obtained a high vacuum easily and quickly. He sadly lamented that the method was useless since the glass bulb was discolored in the process. This was an important limitation in lamps but was not in vacuum tubes, which he had not considered.

After a little experimenting, the Moorehead Laboratories started using phosphorus and was able to get a high vacuum. A paint was made of amorphous red phosphorus and alcohol. A thin stripe of this was painted on the plate of each tube. After the tube was pumped and sealed off, the filament was heated and a high voltage applied between plate and filament. The tube would show a blue glow and the plate would start to redden in a second or two. The operative would watch the stripe and when the color started to travel in it, would shut off the voltage. The glass envelope would suddenly acquire a golden yellow color and the vacuum would meet the specifications.

It was decided that in view of the Italian publication it would not be possible to get a patent on the process and consequently the process should be kept secret. A special room was built with full security protection. Crates of tubes with clear glass bulbs went into the room and tubes with a golden color emerged. The operatives had no understanding of what they were doing. The secret was apparently well kept. About 1922 General Electric came out with some tubes which used phosphorus as a getter but it is believed they worked out the process themselves.

Some six months after starting, the factory was in full operation and continued so until the war ended Nov. 11, 1918. The English contract called for 1,000 tubes a day, all of which were tested by English inspectors. When the United States entered the war they also gave Moorehead large orders. In a Moorehead booklet put out in 1919 pictures of several types of tubes are shown. One shows the original Electron Relay. Some of these were used by the U.S. Army in France but likely were manufactured before moving into the Mission Street factory. One picture shows the "Moorehead Valve Type R (receiving), Standard of the British Government. Another picture shows the SE 1444 vacuum tube "Standardized by the United States Government and used by NC planes in the first flight across the Atlantic." Elsewhere it is mentioned that Moorehead tubes were installed on steamer George Washington upon which President Wilson made his trip to Europe. Radio sets with Moorehead tubes were also installed on several warships stretched out across the Atlantic when the NC planes flew the Atlantic. One of the tubes used on this historic flight was presented to the Moorehead Laboratories soon after the flight. The booklet stated that the Moorehead Laboratories nis today the largest concern exclusively manufacturing vacuum tubes in the world - - being licensed under the Fleming or Marconi patents and the De Forest patents with the right to use the word "Audion". The SE 1444 was used extensively by the U. S. Navy into the 1920s and one of the first jobs that the writer was given when he went to work at the Radio Laboratory at Mare Island Navy Yard in 1922 was to try to discover the cause of the excessive noise which some of the tubes seemed to have.

The filaments used in the Moorehead tubes were of tungsten and had to be operated at incandescent temperatures. The filament was believed to have been obtained from Mallory. The General Electric Co. had previously found that the addition of thorium oxide to the tungsten made it less brittle and easier to handle. On a number of occasions when testing tubes, the Moorehead people observed high emissions at about one-third the normal filament current but this situation seemed transient and unpredictable and no investigation was made into the phenomena which in the 1920s gave rise to one of the important improvements in vacuum tubes. Some of the filaments were crimped, for what reason it had not been determined. The filaments were attached to the stem wires by inserting the filament in a bend in the stern wires and closing the bend with a hammer blow (cold welding). When using ad. c. filament voltage (normal) this was found to give noise when the tube was first operated but decreased with time. When operated on a. c. (unusual) the noise continued for the life of the tube.

The Moorehead organization was geared to the production of tubes and not to development. The scale of production was such that after the war was over there was a surplus of tubes in the purchaser's stock and new orders ceased. The factory was kept open by taking on · various sundry jobs. It designed and built special tubes for research work by the University of California and Stanford University. They took on the job of producing phototubes for a Hollywood man who claimed to have invented talking pictures. The man did not know anything about phototubes so the work had to start from scratch. He was also unaware of the state of development of amplifiers and speakers required for his project. Another man had a similar idea and shortly the ideas were sold to separate moving picture interests who took the matter of priority to court. One of the points of contention was whether the notes of the Hollywood man dated 1919 had been written then or later, since it was contended that "phototube" was not used until 1928. In 1934 B. F. McNamee, the Moorehead engineer who had designed the phototubes, gave evidence before a patent inquiry that all Moorehead products had always been called "tubes" even after they had lost their tubular appearance.

After World War I, Moorehead Laboratories made tubes for De Forest with De Forest's name on them. They were of the same construction as those made for the English except for the conventional arrangement of base pins. When amateur radio stations were again allowed to operated after the war, Moorehead Laboratories made some gaseous tubes with standard bases for sale to that trade. Some time after the war the Atlantic-Pacific Radio Sales Co. was formed for the purpose of buying Moorehead tubes for about 90 cents and selling them to the public for about $5. They had offices on the first floor of the Moorehead factory. Ellery Stone was connected with this organization at one time.

Either this company or the Moorehead Laboratories acted as sales agent for De Forest's line of radio telephone equipment, including a 1-kw transmitter. Some of these were sold to both sides fighting the civil war then going on in China. The equipment sold to the southern Chinese was impregnated and given better insulation in the Moorehead plant so as to withstand the very bad moisture conditions in the area of use.

One sale of a transmitter was made to a San Francisco stock broker. One of the larger stock brokers in San Francisco had the only direct wire stock price service from New York on the Pacific Coast and posted the New York prices on a large board. The broker who bought the radio equipment had several offices in California cities within 100 miles of San Francisco. he is said to have employed a couple of men to take turns copying prices from his rival's board and telephoning them to his radio station where they were transmitted to the outlying offices. Moorehead had accepted the broker's claim of a direct wire from New York and did not know how the prices were actually obtained.

It has been said that De Forest was one of a few to recognize the possibilities of the radiotelephone as a broadcast medium. Most people considered only the military and point-to-point communication aspects. De Forest was involved in legal proceedings in the courts in the New York area and decided to enter into his broadcast venture elsewhere. About 1919-20 Moorehead Laboratories built and operated a 1-kw broadcast station for De Forest in San Francisco. It was located on the top floor of the California Theater Building near l1th and Market Streets and was known as the California Theater Station. One antenna support was located on the Humbolt Bank Building next door and the other on a Catholic church some distance away. The station maintained regular programs of news from 4 to 5 PM and 7 to 9 PM. They also broadcast organ music from the California Theater on Sunday mornings . There was a direct line to the San Francisco Call newspaper office from which world series baseball plays were received and broadcast. A music store kept the station supplied with phonograph records. The call letters were 6XC and it operated on a frequency much lower than subsequent broadcast stations, perhaps around 150 kc.

At about the time the California Theater station was built, the Moorehead Laboratories produced a tube which had been designed by De Forest and which was called a "Singer Tube." It had pure tungsten plates and was enclosed in a bulb similar to that used for 100-watt lamps at that time. It was capable of a power output of about 25 watts. Several of these tubes were used in parallel in series with the plate power supply of the 1-kw oscillator to r:1odulate the California Theater transmitter.

About 1920 the Moorehead Laboratories became insolvent for lack of sufficient business and was taken over by the creditors headed by a Mr. Shaw of Boston who had been supplying bases for the tubes. He looked for capital and to that end entertained extensively at the Claremont Country Club and the Mt. Diablo Country Club. Mr. Shaw and De Forest are said net to have gotten along well. The manufacture of tubes by Moorehead had been under a license from De Forest and Shaw resisted an attempt by De Forest to increase the royalties at a time when the Moorehead Laboratories was struggling for existence. Not long after, both Moorehead Laboratories and the California Theater station shut down. Shaw established a new broadcast station across the Bay in the Piedmont section. Mr. Siguard A. Sollie was one of the operators at this station and the writer became acquainted with him at that time.

The Moorehead plant on Mission Street was left intact, probably with the idea of again opening when conditions were more favorable. The shutdown had come just before the broadcast craze had taken hold of the public and perhaps some anticipation of this encouraged the owners not to dismantle the equipment.

Some time about the early part of 1924 it was decided to open up the plant again. The De Forest patent of 1907 was due to run out that year so a license would not be needed. Moorehead himself had taken to drink and had been forced out of the company when the creditors took over. He was a large blonde man and died about 1924. Just who controlled the company is not known but a Col. Seagrave became President at this time. He was also President of a shipyard at Pittsburg, Calif. and had a San Francisco office. A man by the name of Gunn was the Secretary and / or Treasurer. A Ralph Beal, at one time connected with the Federal Telegraph Co., was on the Board of Directors. It was found that a German by the name of Henry K. Huppert had opened up a small vacuum tube plant in San Francisco and was operating it part time while he secured a steady income as an X-ray technician the other half of the time. He appeared to be the best man obtainable to handle the operation of the factory and so was hired to work afternoons.

The manufacture of tubes was started under the firm name of A-P Radio Laboratories. At first they manufactured only one tube, a 6-volt, 1/4 ampere receiving tube that gave similar characteristics to the 201A tube then being manufactured by a number of firms. The tube consisted of a plate bent to form two tubular sections each of which was geometrically similar to the original Moorehead tube. The grids were connected in parallel and the plates were formed integrally. This tube was known as the 625 tube.

It was soon decided that engineering help was required and the Electrical Engineering Dept. of the University of California was asked for help. The writer, who was then employed at the Radio 1aboratory at the Mare Island Navy Yard, was contacted with the result that after telling Col. Seagrave that he knew something about the theory of vacuum tubes but had never made one, he was hired as Chief Engineer. Immediaely after the interview, he went up the street and bought a copy of Van der Bijl's book on the design of vacuum tubes which had been printed a year or two earlier. He went to work May 4, 1924 after the plant had been in operation for a short time.

At that time there were perhaps 30 employees in the plant, mostly girls to operate the glass machinery, spot welders, etc. There was one glassblower. Later Mrs. Moorehaad applied for a job and was hired. Trouble was being experienced in producing good tubes due to several factors. This was in the early days of the use of thoriated tungsten filament and the handling of this filament was critical. Various unknown factors prevented getting the expected emission from the filament and the only way to overcome this problem at the time seemed to be to experiment with various ways of handling until a satisfactory way was found. All of the tube assembly was manual, with the consequent variations in spacings and characteristics. The company did not have enough capital to buy any large amount of filament at once. It was purchased from various sources, sometimes on spools but more often imported in about 10-inch lengths filling a l/4" ~lass tube and costing about $200. Some of the filament was purchased on Courtland Street, New York while some came from Germany where it was manufactured under the Pintsch patent. Some was impregnated with thorium oxide and some was merely coated. Each batch required more experimentation before successful tubes could be made from it and since for financial reasons larger quantities could not be bought at one time nor ordered well in advance of running out of the last shipment, many inoperative tubes were produced after a new shipment arrived before a suitable method of treatment could be devised. Somewhat later the company produced a small 3-volt, 106 amp. tube coded the 306 which had a filament only .0006" or .0007" in diameter and this filament gave even more trouble.

At first Mr. Huppert endeavored to handle the sales of the tubes but later the Baker-Smith Co., Inc. with offices in the Call Building became the sales agent . Neither was very successful in selling the quality of tube that was being produced in the face of stiff competition that was being had at this stage of broadcast receiver development. So the company went from hand to mouth for about a year without making very much progress. The writer spent all the time he could endeavoring to pinpoint, 1ith the aid of only a few meters, the cases of the difficulties and eliminating them. He did considerable library research in the evenings at the University of California library. From various sources he found that in principle the filament had first to be flashed for a brief time at a fairly high temperature to change some of the thorium oxide to thorium. The filament temperature then had to be lowered to such a value that the thorium would go to the surface and form a one-molecule layer which would reduce the work function of the tungsten and greatly increase the emission. The operating temperature had to be such that the thorium would come to the surface as fast as it evaporated. Occluded gases could greatly affect this layer and consequently the emission. He built an optical pyrometer on his own time and at his own expense to be able to check whether the proper temperatures were being used at the various stages. He also bought a good microscope in the hope that he could learn something about filament burnouts, etc.

About the same time that A-P Radio Laboratories went into operation a number of other companies also went into manufacturing vacuum tubes. The bigger companies had a patent cross-licensing arrangement and discouraged as much as they could the operation of the small companies. A-P received a letter threatening legal action if production continued and lawyers were consulted was filed. No law suit was filed.

Mr. Sol Dushman wrote a series of articles in the General Electric Review on high vacuum which were of great value. It was later heard that these had been reprinted in book form. An attempt to purchase the book from General Electric elicited a reply that there was no such book. One was subsequently ordered from the University of California Bookstore and promptly received.

The A-P tubes used magnesium as a getter rather than phosphorus. A small strip of magnesium ribbon was welded to the outside of each plate and flashed by induction.

The writer conceived the notion of testing the tubes more rapidly by using a cathode ray tube, one set of plates of which would be connected to the grid input and the other across a resistance in the plate circuit. At that time cold cathode tubes could be obtained from Germany and Western Electric had just come out with the first hot cathode tube, a description of which had just been published. The writer resolved to make one of the latter and persuaded the glassblower to spend his own time on a Saturday afternoon assembling one. It was pumped and layed aside over the weekend. First thing on Monday morning the writer went to look at it and found it in a thousand pieces; it had not been properly annealed. He never got around to making another.

About late 1924 Mr. Charles V. Litton, then a postgraduate student at Stanford University, came to the factory and asked for part-time work which he could do without interfering with his studies. He had made vacuum tubes in his well-equipped home shop and probably knew more about making vacuum tubes than I did. He was given several commissions to build wire-forming machines and the like. In 1926 he went to work for the Bell Telephone Laboratories at Deal, N.J. but left in 1927 and returned to California where he soon after founded the Litton Industries.

On several occasions our plant had to be shut down temporarily to wait for material or until problems could be solved. Finally about July 1925 the entire plant was shut down and all factory employees layed off. After about a month the writer went to work for the Pacific Telephone & Telegraph Co. as a Transmission Engineer. A few weeks later he was called on the telephone and asked to return to the A-P Laboratories but refused and the job was taken by Mr. R. C. Ford who had been his assistant earlier.

At this time the plant was taken over by the QRS Kusic Co. of Chicago headed by a Mr. Thomas Pletcher. The firm was already manufacturing tubes in Chicago. Radio broadcasting was killing their player roll business and they hoped to get in on the competition. Mr. Ford was sent to Chicago for two weeks to study their plant and methods and then returned to San Francisco. The plant was moved from Mission Street to a corner of a modern factory at 7th and Folsom Streets where QRS made player piano rolls. The vacuum tube plant was operated for about a year with fair success and then suddenly shut down due to patent litigation.

Thus ended the life of what had been one of the earliest factories for the manufacture of vacuum tubes in the United States.