# Oral-History:Russel S. Ohl

## About Russel S. Ohl

Russell Ohl's collegiate interest in chemistry and electricity led to his pioneering career in radio electronics. A graduate of Pennsylvania State College, Ohl enlisted in the Army during World War I and conducted license service tests for military aircraft radios. After the war, he continued electrical research in batteries and vacuum tubes. He went to work for the AT&T Company and then for its subsidiary Bell Laboratories, building unipotential tubes and a new portable radio receiver. His subsequent projects were in quartz crystal research, high frequency control, interference reduction, and building semiconductors.

The interview spans Ohl's career, concentrating most upon his research and inventions between the two world wars. He discusses his technical discoveries as well as support for and opposition to his work. The interview also examines his attitudes about some Bell Labs colleagues and his post-retirement activities.

## About the Interview

Russel S. Ohl: An Interview Conducted by Frank Polkinghorn, Center for the History of Electrical Engineering, 6 January 1975

Interview #020 for the Center for the History of Electrical Engineering, the Institute of Electrical and Electronics Engineers, Inc.

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Request for permission to quote for publication should be addressed to the IEEE History Center Oral History Program, IEEE History Center, 445 Hoes Lane, Piscataway, NJ 08854 USA or ieee-history@ieee.org. It should include identification of the specific passages to be quoted, anticipated use of the passages, and identification of the user.

It is recommended that this oral history be cited as follows:

>Russel S. Ohl, an oral history conducted in 1975 by Frank Polkinghorn, IEEE History Center, Piscataway, NJ, USA.

## Interview

Interview: Russell S. Ohl

Interviewer: Frank Polkinghorn

Place: Vista, California

Date: January 6, 1975

### Education and interest in radio

Polkinghorn:

This is a recording made on January 6, 1975 with Russell S. Ohl at his home in Vista, California. The recording of the interview was made by Frank Polkinghorn with Reginald Vax assisting. Russell, we are going to try to make some recordings of the reminiscences of old-time electronic and electrical engineers, and I would like to start off with you. I believe you said a few months ago that you would soon be seventy-seven years old; that's when?

Ohl:

This month.

Polkinghorn:

Where were you born?

Ohl:

In Pennsylvania. Near Allentown.

Polkinghorn:

Tell us about your schooling--your grammar school, high school and so forth.

Ohl:

Polkinghorn:

Did you start as an amateur radioman?

Ohl:

No.

Polkinghorn:

I thought that I understood that you had. Okay, go on with Pennsylvania State.

Ohl:

I went to Pennsylvania State and I was very raw. I didn't know anything about how to behave; I was sixteen years old. It was a new experience, so I picked up the subjects that I liked best, and those were chemistry and electricity. I a took course in electrochemical engineering. This was reputed to be so difficult that the senior students of whom I was acquainted were discouraged, but I persisted. Nine of us were registered in that course, and at the end of the freshman year there were three of us remaining. So from there on we went on. In my sophomore year I saw a radio receiver, a real honest- to-goodness receiver for the first time.

Polkinghorn:

What year would this be?

Ohl:

This was in 1914. Possibly 1915. I would have to figure that out.

Polkinghorn:

It's all right.

Ohl:

I heard an S.O.S. from a ship at sea that was being attacked by a German submarine. I heard it on the crystal detector and also on the DeForest Audion. At the time the DeForest Audion was considered possibly less sensitive than the crystal detector. So, from there on I had nothing more to do with radio until my senior year and then J. O'Brien came to the college. So seniors in the electrical engineering school could take a course, a government course, in vacuum tubes.

Polkinghorn:

Where was the course being given?

Ohl:

At Penn State. We were given full credit for it. I took that course and that was when the radio bug bit me. I never got over it.

Polkinghorn:

Well, you could do worse.

Ohl:

I wasn't sure about this stuff that was being told me. I was a member of a chemical fraternity, Alpha Chi Sigma.

Polkinghorn:

I lived in the Alpha Chi Sigma house at one time.

Ohl:

You did? I discussed this with the fellows in the fraternity and they said, "Well, let's try it." I got a piece of silicon from my electrochemistry professor and he gave me a piece of piano wire. I rigged that up and another one of my fraternity brothers had a Murdock receiver. We dug up some wire and ran it along the ceiling and connected the receiver and the crystal detector series to the radio. They said along about 12:00 there would be some signals from Arlington, and lo and behold we got them. On the first try we got those signals. I said to myself that there must be something to this radio business. That year we had no vacation. We went right [through?] the school year, no Christmas vacation, no in-between term vacations, nothing. We were graduated on April 24th and those who took the government course stayed there two more weeks to finish the course under J. O’Brien.

Polkinghorn:

This is all on account of the war?

### Army service and early employment

Ohl:

The first job I got was with the Electric Storage Battery Company, in the research department. I was assigned to the development of a 320-volt battery to operate the SCR 68 telephone transmitter on airplanes. Well, we did that successfully and made some sample batteries. We sent them off, and at about that time, I got pretty fed up with battery stuff. Too many people got lead poisoning, it was too much trouble working with vitriol and that sort of thing, and I got tired of it. In the meantime I had another offer from the Westinghouse Lamp Company in Bloomfield. I wrote to them; they said the job was still open so I made a change. I went to the Westinghouse Lamp Company and was put in lamp development. Well, that was pretty slow, so I started making vacuum tubes on my own.

Polkinghorn:

Was Tony Lederer there at that time?

Ohl:

I don't think so. Dr. Shackleford was head of the physics department. Well, after I had been there for a while working on incandescent lamps, I really knew all I needed to know about them. I could make them, design them, lab test them, and write the specifications for them. Then I got transferred to Dr. Shackelford's department in the physical laboratory. There I made vacuum tubes, and while I was there I made some one-kilowatt vacuum tubes, which we operated at a two-kilowatt level. We used those tubes as the driver for an induction furnace. It was probably the first continuous wave induction furnace that was ever used for treating vacuum tubes.

Polkinghorn:

What year would that be?

Ohl:

Polkinghorn:

Tell us how you happened to get from where you were to Colorado?

Ohl:

The Westinghouse Company got chicken on the radio program and decided to abandon the whole business. The men who were working on it were simply laid off.

Polkinghorn:

I see.

Ohl:

But Dr. Shackelford and Dr. Lester told me about a teaching job at the University of Colorado. They were anxious to have an instructor immediately, and I applied for that job and got it with their recommendation. I was only out of work for five months. Just long enough that I got married. I had known my wife for a number of years.

Polkinghorn:

Well then, how long did you teach out there?

Ohl:

One school year. At the end of that school year I was offered a contract to keep on teaching there, but Dr. Brian called me from New York. He had been appointed head of the personnel department, and he called and said they wanted a man immediately who knew something about radio. They wanted him in the equipment department of the AT&T Company. He talked to me at length on the telephone. We finally got to the point that I consulted the head of the graduate school -- this was the 1930s-- of the university. He said that the contract was available for the following year, but it was a good opportunity to get into radio in the New York area. He liked it there and he was a friend of John J. Hellington. It would not be a mistake to do it, to make this change. So I went home and my wife had thought about it and she said, "Good. Let's go to New York. I never did feel good in this high altitude." So what could I do? She decided for me, so that is how I got to AT&T.

### Employment at AT&T

Polkinghorn:

You were at AT&T for several years before you went to the Bell Labs.

Ohl:

Five years.

Polkinghorn:

What did you do while you were there?

Ohl:

I did almost everything there was to do regarding radio. I first suggested making equal potential tubes. That was with Hank Holenheim. We got an appropriation of $75,000 through the AT&T Company to get the Western Electric Company to make some samples. Western Electric had made some of what we called unipotential tubes, and of course I got the first samples. M.J. Kelly made them. With those tubes I was able to construct a portable radio receiver that was powered solely from sixty cycles. That was the first one. That went to Lyman Morehouse. He was very much impressed with it, and it resulted in further development of the unipotential heater type vacuum tubes. Polkinghorn: I believe Morehouse was from California. Ohl: Yes. I was also interested in a number of other ventures, such as the control of high frequencies with a quartz crystal. I obtained a quartz crystal from the General Radio Company and they had obtained it from Professor Pierce at Harvard. Then I had constructed a fifty-watt transmitter in my apartment and was transmitting all over the country with that. It was getting good results with the voice, which was difficult to get those days. You couldn't get good results on the voice in short waves. A difficulty came up; they wanted to get a radio system installed in Mr. Thayer’s residence. He was president of the AT&T Company. And we were sent up there. D.K. Martin, he was a transmission engineer, Gillett, I forget his first name. Polkinghorn: Glen. Ohl: Glen Gillett and myself, I was sent up as an equipment representative and found everything in order. Everything was working fine but it couldn't get any ineligibility from that voice that was broadcast from Station WBAY in New York. WBAY was a forerunner of WEAF. The transformer was made as a result of our investigations, but while D.K. Martin and I were out one night investigating, I said to Martin, "You know, this thing reminds me of the kind of interference that you would get with white light coming from two different paths. I wonder if we aren't getting that same kind of trouble from the skyscrapers that are in the way, between the transmitter channel and Mr. Thayer’s." He agreed and said, "That might be changed with difficulty. Let's investigate that." He got the transmitter transferred to West Street and the programs were transmitted at West Street. Polkinghorn: Where was it before? Ohl: On Walker Street. Which is now Polkinghorn: The Long Lines building. Ohl: The Long Lines building. They talked from West Street and their station call letters were WEAF. That is where that call started. The voice conditions improved, all right. There was strong evidence that the skyscrapers were splitting the wave, so they moved it back to WBAY and changed the length of the wavelength, but it didn't do much good. So they moved it back again to WEAF at West Street and that was the last time it transmitted the voice from Walker Street. I had been getting such good results on short waves with a quartz crystal control that I suggested to Martin that they place the WEAF transmitter on the quartz crystal control. Martin got busy and worked with Ray Heising, I think, to get the WEAF transmitter on the quartz crystal control. They made a test and notified all the AT&T engineers that on this particular day they were going to run an AB test. They got the test results through and there were no exceptions. The A was the best quality and it the quartz crystal control, and that was the end of the old five hundred watt self-excited transmitter. I think Oswald then produced a box with a quartz crystal in it that could be sold to all the people who had these Western Electric transmitters installed. They could be placed under quartz crystal frequency control. So that's a thing of its own. Then I built a transmitter that was used for investigating, making a survey of New York Harbor. That survey was made covering the range of seven and a half meters to 106 meters in steps. Those were all crystal control. That was done by Southworth and I think C.N. Anderson, although C.N. Anderson and I had made a preliminary survey before that, not covering quite as much range. I had also built a transmitter for Southworth's expedition to the Bermuda islands. He and another fellow took a receiver on the ship, to the Bermuda Islands. I transmitted from Walker Street and the schedule was so tight that we had to take apart of a Western Electric transmitter and put together the same transmitter and get it on the air by 11:00 that night. We did; we worked around the clock to get that transmitter going because he was on the Queen of Bermuda or something like that and he was out at sea and he had to get the signal. He said that they got signals clean into the harbor and when they got into the harbor, the radio operators were astounded because they had not previously received signals there, not even 600 meters. Here these thirty-three meter telephone signals were coming through like a house afire and clear as anything. Everyone read it in the newspaper reports and all that sort of thing. I think Gillett there was with George Southworth; that was the time I passed on the message to Gillett's wife had had a child, and they got that message. Polkinghorn: Up to Cape Cod. Ohl: The next step was that this short wave shack at Deal had been built, showing how to be authorized to build that and operate it. Well, we were going to run transatlantic tests and they were supposed to be made from the transmitter at Deal. They were, but they could only get down to about thirty meters or something like that, so then I was called in to operate on twenty, sixteen, and thirteen meters. We transmitted across the Atlantic from the Walker Street building. I built a shack on the top of the building and we used the old towers and got the linemen to put high antennas up there, you see. We used those antennas and we transmitted across the Atlantic on that and Southworth established the jump distance one the very short waves. We could receive thirteen meters for a very short time at certain times of the day. Then we transmitted some signals from Sloan University Laboratory in 1925 during the solar eclipse. Southworth was out in Long Island and D.K. Martin was receiving them down at Stanford. The transmissions that I made were again on short waves in that period and they were able to establish that as soon as the sun is blocked off, the ionosphere is almost immediately altered. Polkinghorn: Altered. Ohl: During this period there was interest in semiconductors. This is interesting. In 1922, Brondoll had developed the copper oxide rectifier. Demarest came back from a Physical Society meeting in Washington and told me about this. So, I said all right, let's get some of these rectifiers and see what we can do with them. The company was able to get a rectifier from the Westinghouse Company and spare disks and I looked into this thing and at that time we were interested in getting a current supply for a receiver that ion end tube receiver, that they used in 1A.... Polkinghorn: 1A, yes. Ohl: Superheterodyne receiver. We wanted to get a power supply for that, and Morehouse was very interested in getting this power supply. So I was able to take a rectifies and change the assembly of the units in that. By coating the surface of the thing with graphite, I was able to raise the current capability of the thing so that it would just feed that 1A receiver. And I built a low pass filter out of telephone coils and condensers. I remember it had about an eighty-decibel attenuation for sixty cycles. He took this home with him and put it on his 1A receiver and he said that just worked fine. He says that there was no indication of sixty cycles. Now this sparked off something that was very important because after that the equipment department became very much interested in the possibilities of using copper oxide rectifiers in the telephone plant to replace batteries. They had sponsored the Western Electric research into making these copper oxide rectifiers. The fellow who was first assigned to it was a fellow by the name of Sigmund in Becker's group. Polkinghorn: Yes. I know Sigmund. ### Laboratory research on high frequency radio Ohl: He was first assigned to that work. That was the beginning of it. Oh, another thing about these copper oxide rectifiers: I had been working along with them and I wanted to find out if they could be used to rectify high frequencies. I took some up to the shack in the Long Lines Building and I used the power of the transmitter. At that time we had a 250 watt final transmitting tube and I took the full power of that at seven and a half meters and put it into this copper oxide rectifier, trying to make it work. Finally, I got one microampere out of it and shortly after that I heard an explosion and the surface had cracked to pieces. That taught me that copper oxide rectifiers could not be used at high frequencies. It was a very important step because later on when I actually went after the research in high frequencies hammer and tongs and I knew this, and I had an awful time convincing Pierce that it couldn't be used. J.A. Becker, who was head of the physical department, also couldn't be convinced. Walter Brattain was the first convert who saw the difference between a point contact rectifier, and the evaporated type, which was used with the copper oxide and selenium rectifier. He was the first man to recognize that. After that it was easier because I had some support. Well, anyway, we are getting ahead of ourselves, and that puts an end to that. Then they wanted me to transfer to carrier. But I was not interested in carrier really. I came to the AT&T Company because I wanted to go to high frequency radio and I told Demarest this was what I wanted to do. So he said, "Well, have a talk with W. Wilson." W. Wilson was very much impressed with my vacuum tube experience and these other things, so he took me right up to H.D. Arnold and H.D. Arnold said, "Well, Ohl has caused us so much trouble with his patents. The laboratory transfers are going to be worth it; go ahead." And I requested it and that is how I came to the laboratory. I was the only one in the D&R who was transferred to the laboratories before they were combined. Polkinghorn: Yes. I remember when you were transferred and that was about the time Holmdel started. No, before that. Ohl: Yes, before that. Polkinghorn: Before Holmdel started. Ohl: I was transferred to Clifford. Polkinghorn: But it was after March 1927. Ohl: It was in June. Polkinghorn: June, Okay. Because I came there in March of 1927. I know you came afterwards. ### Transatlantic project and waves interference Ohl: June 1, 1927. I started in on this transatlantic project trying to find out what we could do to cure the trouble. We knew what it was, the interference in the waves. We knew what the causes were and how they operated it. But we didn't have any way of combating it and my job was to try to build some kind of equipment which could get us around this problem and give us an understandable signal. I started in with multiple antenna work and then we placed antennas all around, three antennas at different places around the property. At first, we studied the fading and we received telegraph signals and we were able to record these telegraph signals in synchronism. In that way you could tell when one was fading out and another one was coming in. By taking these records and compiling them we had an indication that if you combined these three locations in the proper way that you could have a reasonably steady signal. That was when we moved to Holmdel. Polkinghorn: I remember that move very well. Ohl: It was January 1930, when we moved to Holmdel. Polkinghorn: I couldn't remember exactly when it was. Ohl: Early in the 1920's, there was some difficulty with telephones that were located near the station KDKA. They were transmitting on a box at 107 meters or something like that. Whenever they transmitted they made the telephones inoperative. So, the chief engineer of Bell Pennsylvania and I set up circuits between his place in Pittsburgh and my apartment in New York. When this station came on, I would notify him when I received KDKA. Then he would monitor the telephones. Well, we tracked this difficulty down. He didn't know what it was at first and he traced it this short wave station. Then we investigated to see what we could do to clear the telephone system of some of the interference. They found that the trouble was due to the demodulating effect of the carbon granules in the microphone. It was very simple to cure this by putting in a condenser and inductance filter at the proper place in the telephone instruments. So that cleared that situation. Polkinghorn: Yes, I remember that was quite a problem at one time. Tell us about when you went to Holmdel. We were talking a little while ago about the recondition carriage. Tell us a little more about the work you used to do there. Ohl: Oh, yes. Polkinghorn: And that connection. Ohl: The work. ### Equipment adjustments to improve high frequency reception Polkinghorn: Audio File MP3 Audio (020 - ohl - clip 1.mp3) All the ways that you investigated there to try and improve high frequency reception. Ohl: When we went into Holmdel, we really dug into this situation as to what we could do from the equipment to clear up the voice. We developed triple detection systems and that sort of thing so that we could do things to the intermediate frequency, like control the frequency and control the phase and all that stuff. This developed into quit interesting systems. The first thing it did was to build up a constant frequency oscillator. To build that up it had to start with a zero temperature coefficient crystal. Bond made that for us in Heising's group. Then we put that in a larger copper bomb and had that copper bomb on temperature control to 104 degrees. He set the whole business in a box and this temperature control could tend to the degree and the output of that unit was one megacycle. Later we were able to calibrate this from a thousand cycle signal which originated in the Naval Observatory in Arlington and was transmitted to West Street and from West Street transmitted down to Holmdel. We multiplied that up to a megacycle and we united these two frequencies. We could hold that thing steady so that you had a meter that would indicate cycle difference, just a fractional difference in the tube. We could get that meter just to stay in one position for considerable time, maybe a matter of a half an hour or so. There would be no changes. This was our constant frequency source. We stepped up the one megacycle to near the short wave carrier frequency, say twenty megacycles, and we added to it from a very stable vacuum tube oscillator that would oscillate in the hundreds of kilocycles range. That was temperature control and the inductance for the toroidal coil that they had made for that with a very high Q, so that the frequency would not wobble. We added to that to get a very stable signal. The first thing that we developed was a servomechanism and it was probably the first servomechanism that was ever used to stabilize radio frequencies. It was a Leeds and Northrup recorder and had moved a condenser. Polkinghorn: I remember that well. Ohl: It was connected to this very stable low frequency oscillator. With that we were able to hold the frequency of the incoming signal steady and we were able to record it. One of the first visitors to the laboratory to see that was Appleton from the British Post Office, and he was amazed at the jumps in frequencies we observed in their station. We were able to show other stations with the same apparatus that did not have the frequency change. That was the first knowledge that the British had that their frequency not as stable as they thought it was. It was quartz crystal controlled, but it jumped. So when he returned to England he told them. Well, from having this stable control and incoming signal they were able to take this signal, and run it through filters and lop off for the sidebands. They were able to take a single sideband and introduce a new stable carrier and get good quality. This had been developed to the point that we finally had two receivers. We had three antennas but maybe we had only two receivers. We were able to take signals like this and we were able to take a transatlantic signal and receive it single sidebands or double sidebands with a re-supplied back carrier, or we could receive it, in a third method that we used. I forget what the method was. Polkinghorn: You could take it either sideband with or without carrier or could you proceed with double sidebands. Ohl: We could receive a signal side band with a smoothed-out carrier or with a re-supplied carrier separately, and we had arranged a demonstration of that. We had two long tables in the laboratories. Attending were Frank Polkinghorn, A.A. Oswald, H.D. Arnold, W. Wilson and Frank Kahn, C.R. England, and so forth. These people were all seated along this table. They each had a single receiver. They had a little switch in front of them that they could switch and receive single sidebands with the carrier or with a re-supplied carrier or they could receive double sidebands with a smoothed-out carrier. Just flip the switch. Now you were there and you perhaps remember. Polkinghorn: I can’t remember about that particular incident but I can remember being with a gang like that on some occasions. You recall I was down there every Friday. My job was to go around and find out what you fellows were doing and consequently I can't remember specifically particular things. I could remember the trend of things that I learned, but what happened at a particular time I did not remember so well. Ohl: I am still amazed at the speed at which we put those cables together. Cables as thick as your arm, you know, full of high frequency current. Sam Reed built them and put them together. How we ever kept those wires separated I'll never know. Polkinghorn: You first had frequency control with a recorder and then you had one with a little condenser on a meter needle capacitor, I remember. Ohl: A funny thing happened there. One of the objects was to synchronize two of the signals from two antennas and the reason for synchronizing is that the carriers would go out of phase and they couldn't combine them in the same detectors that way. It could give you a mess, so we had devices for synchronizing these two signals. The thing that impressed me was a circuit that came to me when I was asleep. The whole circuit came to me and I went into the laboratory the next morning and drew it up and it was a complicated thing. It used semiconductors, copper oxide, and small disks that were made by the General Electric Company, and it used those things in such a way that this thing would automatically give you absolute phase synchronism, between the two signals without having any moving parts. We proved that by putting it on the oscilloscope and watching it there. I always liked that. We had also tried mechanical means of having synchronous motors. We built special synchronous motors, miniature ones, only an inch in diameter, and they had a terrific speed of recovery. One of the things that I ran one time had a 12,000 rpm. We tied the things on two shafts. One end of the shaft had the synchronous motor, the other end of the shaft had two intermediate signals from two different antennas. That motor was so fast it could hold those two intermediate signals in step, and that was another way we did it. But that took a lot of doing; it was so hard to make that sort of thing and the copper oxide method was so simple by comparison. I always favored using copper oxide. That was kind of lazy and I liked the easy way. Polkinghorn: Now we come I think, probably, to the war era. Ohl: Not yet. Polkinghorn: Not yet? Ohl: Just a minute. Then there was agitation to try out this RCA system. King was put on that job and he was to make three identical receivers, make or get them any way he could get a hold of them. Receive the signals with diversities and then we were to compare that with the methods we had established for using the frequency control. Well, the upshot of the thing is that we got the best results using diversity on the re-supplied carrier because the diversity did not distinguish between the phases of the carrier as it would come in. At certain critical times it would get hashed up and the re-supplied carrier with its corrective phase going in there and using the diversity corrected that. So that gave us the ultimate best result we could have with our equipment. Then I wrote a final memorandum, and in that memorandum I pointed out that the real solution to this thing was to have a cigar-shaped antenna, a directive antenna with a cigar shape, that we could raise up and down. Rubert Friis took it from there. Polkinghorn: And made the Muse's statement? Ohl: Yes. After Friis got the Muse’s system, he asked me (I guess Wilson was in back of it) to investigate the high frequency end of the spectrum, to open that up, to see what we could do. You see, they couldn't do anything with it. There was no technique for transmitting voice with the high frequency part of the spectrum. I mean the millimeter range. They couldn't do anything with that, so the job was offered to me, and that was what I was waiting for, to do that research work. I plunged into that and the problem was that there were no transmitters and no way of producing transmitters except for the magnetron, and I couldn't make magnetrons at that time. There were no detectors, no broadband detectors, and there were no parts to make transmission tests or anything. We started from scratch, and the first thing I did was investigate all the methods of transmission that had been used in the past. I duplicated Nicholson Tear’s apparatus, I duplicated Hertz's stuff, Art Cadevas methods of generating these short waves and some of the others. They were dummy sparks. Not having a magnetron available, it was a special job to make a magnetron work and have very, very small power. I wanted something that I could get enough power from to investigate the detectors. Well, finally I found that these sparks generated so little power that was impractical, and finally I made one that used a 100 megacycle source that was damped in a regenerative oscillator. It was periodically damped and with that I was able to get hot sparks continuously. In order to get millimeter waves, you had to use a short spark gap, and a short spark gap is a gap that is so small it is just about the mean-free path of an electron in air, in atmospheric pressure. It's about a thousandth of an inch. In order to get this energy onto the short spark gap, since you couldn't use high voltages and you could only use about 300 volts, we had to have a lot of sparks. By using this high frequency that was quenched I increased the power something like 100,000 times. Then we had power that we could use on detectors and with lenses and all that sort of thing. I worked with crystal detectors... Polkinghorn: What year are we talking about now? Ohl: It started in 1934. You see, I worked out the methods of handling the semiconductors and making a crystal detector on a commercial basis. It never had been done before on an instrumental basis. Polkinghorn: Most of that work was right after the war, wasn't it? Ohl: No, I had worked this out before the war. The English got all that stuff from us in the later 1930's. Polkinghorn: Yes. Ohl: But we had already done the groundwork there, you see. It had gotten to the point that we could manufacture stuff. We learned how to cut the semiconductors, we learned how to put back plates on it, we learned how to solder them, we learned how to use certain specific kinds of metals to make contact, we learned how to surface them, and I can tell you an awful lot about that. Fellows like Storks were very helpful in learning how to condition the surface. E.E. Thomas was very helpful in doing the microscopy, and at that time Pfann would just listen on things; he was just getting an education. Polkinghorn: Who was this? Ohl: Pfann. Polkinghorn: I don't remember him. Ohl: He was a guy that worked out this zone melting. Polkinghorn: Oh, yes. Ohl: Zone melting, you know how I got that? Zone melting came about because he was the observer on the thing, and Jack Skaf and I with Henry C. Theuerer's help had worked out some methods of re-crystallizing silicon in order to get the impurities out of it. But we couldn't get germanium at that time and we had to work with silicon. It was a hard thing to do, and the first experiments on that purification of germanium were done quite a while after we had done that work with silicon. Polkinghorn: I see. That was after the war and the other was before, is that what you are saying? Ohl: Our work was before the war. Then in 1940 I discovered the PN junction and contrary to the laboratories’ publicity, I found that all by myself. I did most of this work all by myself, I couldn't get help. Polkinghorn: I remember coming in and talking to you about this stuff, but I didn't remember just when. However, for your information the other people who were working on the transistor, Shockley and.... Ohl: Polkinghorn: Ohl: Polkinghorn: Yes and Bardeen. They have come right out and made some statements that your work was fundamental to what they did. So, I think from their viewpoint that you have gotten credit for it, but I don't think otherwise you have. Ohl: Well, I never held back information. If there was somebody in the laboratory whom I thought was entitled to know, I told them. This was contrary to the policies of some other fellows in the organization, whom I won't mention because it would reflect badly on me and wouldn't do them any good either. Nevertheless, there were a great many enemies to this work with semiconductors; you have no idea how many people opposed that. Vacuum tube people said that there is nothing to it and it is all a lot of tommyrot, and that sort of thing. There was one man who stood out, who had authority: it was Bill Wilson. He backed me and there were so many other people in power like Barkley, you know. At first there was Kelly. Barkley was in my office one time and I was explaining some things about the short gaps and that we were getting auto-electronic emission. I was showing him curves and things. He cut me off sharply and said, “You don't know what you are talking about.” Then that got Kelly's dander up and he very politely informed Mr. Barkley that he was not informed at all and tried to say that what I was saying was correct. But you had to fight this sort of thing. Another man who was very helpful was A.M. Curtis. Polkinghorn: Austin Curtis. Ohl: He gave me a copy that he had of, I think it was Electrician. It was a British magazine, one of these big paged things, you know. In it was a translation from a Russian paper in which they had used Carborundum with two contacts and a battery supplying one of the contacts and had gotten a power gain of ten times. And this was way back in the 1910s, so the fact that you could get a power gain had been known, but it was never put on a controlled basis. I knew about it because an operator of the Signal Corps back in 1919 had told me that some of the operators used Carborundum as oscillators for receiving. When I had seen this article that Curtis gave me, I was not astounded because I had known about this before I ever saw the article. I had heard about it. I knew a former first sergeant in the Signal Corps who had lived in, the boarding house that I lived and he was an expert radio operator. He told me a great deal about the use of crystal detectors on ships. He told me that professional operators carried two crystal detectors with them. One of them was made of Carborundum and one of them was something like galena or something of that sort. He said the Carborundum was used for two purposes. They used it in the harbor when they were close to a transmitter to prevent burnout. Polkinghorn: Right. Ohl: They also used it at long distances with two points. One point was excited with a battery and they were able to get long wave oscillations out of it and in that we were able to be in long wave telegraph stations. Polkinghorn: What was this man's name? Ohl: I have it written down someplace. Polkinghorn: The war came along and we had to have these pieces of equipment, and that's when I recall you picking around the point contact rectifiers. Ohl: Well, there was a reason for that. I looked into the theory of these rectifiers. There wasn't anything written about it; it had to be worked out in speculation and I did a lot of atomic calculations on these things and looked at the crystal structures and got the distances that were involved and all that stuff. One thing stood out, and that is, if you used a thermionic device you faced the situation that the electron transit time varied with the square of the voltage supply. Thus, to get the transit time up, your voltage would rapidly go to fantastic values and you got a voltage radiant that would cause auto-electronic emission, and when you got to that point you couldn't control it, and it was very noisy. So, I concluded that the answer to a device which could rectify or act as a nonlinear device for millimeter and centimeter waves would be one in which the distances were much smaller, and you could visualize being able to make them using an electronic device. This turned out to be the case with the semiconductors. When I investigated on a theoretical viewpoint, I found that the distances were many, many times. They were beginning to get into multiples of atomic distances, you see. They were so small compared with what you could get in electronics that electronics just wasn’t in the picture. Now it was some time before I got Friis convinced that the crystal was the thing to use at ten centimeters. He wouldn't take my word for it, and he spent a lot of money on vacuum tubes. They spend maybe$100,000 on making special vacuum tubes and going to all the trouble of feeding the films and doing this and that. Finally they and used the crystal, so much cheaper and simpler and more efficient.

Polkinghorn:

Well, right at the beginning of the war as I recall it...

Ohl:

Ever since the beginning.

Polkinghorn:

You were developing point contact. You devised some means for driving it into the crystal.

Ohl:

Now, the trick to making a successful point contact device is very simple. You had to make it so that you could have a constant pressure and it would stay in one position and wouldn't have any desire to go to another position. To do this, and it takes a little doing, at first we had to some way of fastening the crystalline material and then we had to make a uniformly active surface which had to be perfectly flat. Then we had to place a point on there in such a way that the mechanical force wouldn’t tend to make it skid around. The S spring was the answer to that. The S spring was sponsored by the British, but I made the theoretical calculations on it from basic considerations and I was able to prove that that spring in small increments would stay right where you put it. I wrote a secret memorandum for that and that never got beyond the laboratory. See, all this work was secret work and I have copies of those memorandums and they have been declassified since that time. Since their usefulness was gone after the declassification, they never did get circulated except, to authorized people. They got to MIT and they got to the specification people, the Shoemaker group, and it was sent to the printers.

Polkinghorn:

What are you going to do with your papers?

Ohl:

I don't know what to do with them.

Polkinghorn:

The Smithsonian would like to have them.

Ohl:

Well, they are going to send a representative out here this month.

Polkinghorn:

They are? I see. So you are already in contact with them.

Ohl:

Yes. Mr. Finn said to keep everything in abeyance until either his representative would come or he would come himself.

### Karl Jansky

Polkinghorn:

Yes. You were around when Jansky made his experiments and presumably started his astronomy. Are there any comments that you would like to make on that?

Ohl:

Polkinghorn:

Yes, I know the brother.

Ohl:

Well, his brother was friendly with the editor of Electronics.

Polkinghorn:

Yes, Don Fink at the time?

Ohl:

I don't know what his name was. The brother got the editor interested and the editor took it up. He was very much interested and he went to Bill Wilson and told him that if he didn't publicize his work the Electronics people would publish it independently. He practically used a strong-arm method on him. Jansky finally was told to get the signals ready so that they could be broadcasted, and they were broadcasted by the laboratories under that kind of pressure. The publicity that Jansky got out of it was sparked off by his brother. His brother followed it up.

Polkinghorn:

I didn't know that.

Ohl:

Jansky was a very modest man. He was an awfully nice fellow, and I liked him very much.

Polkinghorn:

I always thought he would have never discovered what he did if he hadn't had a broad enough background to start playing with the spherical trigonometry on the thing.

Ohl:

A lot of the people who find these things don't try to push it; they know what the shortcomings are, you know. It might not be, and that sort of thing. Jansky was not one to push it, and I knew him all through things. He was very sad when they didn't let him continue his work and put him on getting a little noise amplifier. I don't know who gets these silly ideas, in the research department, but here are people who are knowledgeable in a certain subject and they get to know more than anyone else in the world on it. And they stop him from doing that work, and tell him to do something else. This I don't understand.

Polkinghorn:

Well, it's true. I think a lot of people run out of information and ideas and those kind of people you have to stop. But there are other people who...

Ohl:

Jansky didn't.

Polkinghorn:

Yes. One thing that happens, of course, is if a man starts out on a research project and goes ahead and is the expert on it, pretty soon they move him over into the practical application of that and he no longer is a research man. That happens very regularly.

Ohl:

I know that happens. If you want to stay in research you have to be able to produce steadily. But Jansky could.

### Post-war research and retirement

Polkinghorn:

After the war, what did you do?

Ohl:

My research work was constantly being interrupted. Friis would say, "Won't you make this? We have a government contract. Can we depend on you to produce a dial for the converters or something like that?" He “didn't want to interrupt research, but” and the “but” would take command. Then towards the end of the war Bonts said, "It just isn't right. Do you thing some man ought to have the right, the privilege, of working out the merits of his own finding." He was thinking of the NP junctions?

Polkinghorn:

Yes.

Ohl:

He let me do some work on that and I was working on that. Friis said, “Well, we have this contract with the Air Force. We have to have these things; we can't work without them--the detectors, of course, millimeter weight.” Being by nature the way I was I didn't want a monkey wrench in the works, so I said, "All right. I'll do that." So, then they moved this over to the Roberts House. Friis I know tried three or four times to get rid of me; he didn't want me in that crew.

Polkinghorn:

I know very well, because I was in that position.

Ohl:

You were?

Polkinghorn:

Very much so.

Ohl:

Now, after the war then we had these Air Force contracts, but I did research to the extent that I could. Kelly evidently was not an enemy to it, but whenever he could he put in a good word. For instance, I was to go to Shoemaker's group. Kelly made a special trip to Shoemaker and said, "He doesn’t want to be transferred down here. Forget it." And that was the end of that. You see, there was a lot going on behind the scenes that I didn't know anything at all about. I don't want to say anything more about it because I don't absolutely know. I mean I just guess.

Polkinghorn:

You were in a situation where you were interested in your work and you didn't want to be bothered with the diplomacy of the thing. I knew what was going on.

Ohl:

Then Skaf told me one thing, and this statement sticks in my mind. He said, "I have been through this stage with the copper oxide work. They took that away from us. Mark my words, they are going to take this diode business, this NP junction business and all that sort of thing, the silicon work. They are going to find some way to take that away from you." He was talking about the people in the physics department, and that's what they did.

Polkinghorn:

I was the official contact with NRL and all that work that you were doing. Schaff was doing it effectively because they were supplying the stuff with Schaff.

Ohl:

He was in between them.

Polkinghorn:

Yes. Well, what else can we say?

Ohl:

After the war a new era opened up. I went over to the Roberts House and then I started research again. I was kind of free then. I started doing some work that I had heard Henry Theuerer had done. He had made a surface of silicon photoactive by heating it to a thousand degrees in a closed container, in a quartz container in the presence of phosphorous. He got photo activity. Well, I tried with only red phosphorous and I didn't get any activity. I said maybe the answer to this was to seek out and find some way of getting that phosphorous into the surface, pushing it with an electric field. So, I started building up an apparatus. I had quite a complicated apparatus and I was able to make phosphorous vapor and put 800 volts on it and drive it into the surface of the silicon. And lo and behold I made a darn good photocell and darn good transistor cells. Jansky was assigned to the job to make the first test on those transistor cells.

Polkinghorn:

What year would this be?

Ohl:

Polkinghorn:

This was something that you have done recently.

Ohl:

I just finished it about a week ago.

Polkinghorn:

I see. What are you going to do with that? Write it up?

Ohl:

I have so much stuff that I could write up; I don't know.

Polkinghorn:

Let's see. You moved out of Roberts House and went up on a hill and worked up there, didn't you?

Ohl:

No. I had a laboratory and Kelly evidently had something to say about this. They built that new laboratory next to the Holmdel place.

Polkinghorn:

Yes.

Ohl:

First thing I heard was that this wing was supposed to be mine in the laboratory. I said to Friis, "Oh! You are just joking." "No," he said, "This is for you." I said, "I'll believe it; when I see it. I don't believe it, I have been working in a rear end of a barn for so many years I can't even see having a decent laboratory to work in." Now, where that ever came from I never knew.

Polkinghorn:

Did you move in?

Ohl:

Polkinghorn:

You retired at sixty, then?

Ohl:

I was almost sixty-one.

Polkinghorn:

And you didn't move out here at that time, did you?

Ohl:

To Cambria.

Polkinghorn:

So that would have been 1962?

Ohl:

1958.

Polkinghorn:

1958? Yes. Well, I had forgotten that you had gone so early out there.

Ohl:

You see, I had put my house up on the market. I had it up once before. I was going to move to a smaller one, but I had it up this time for earnest. I thought it would take at least six months or maybe longer. It turned out that it was sold in two weeks. I was left high and dry without anyplace to go to. A guy wanted to move in so I quickly wrote a letter and told them I wanted to be retired in thirty days.

### Recognition and patents

Polkinghorn:

I see. Well, you were elected a fellow of the Institute of Radio Engineers, I recall.

Ohl:

In 1955.

Polkinghorn:

Did you have any other honors of this sort?

Ohl:

No. Nobody ever recognized this work. Through all the war, every Tom, Dick and Harry got a Navy medal. I never even got a "thank you", and I had all this stuff under construction. I wrote the specifications for it, I got all the information to Jack Schaff, gave it to the British to get them started on it, and furnished them with the material. I never got a "thank you" for it.

Polkinghorn:

No patents?

Ohl:

Well, I got patents. I have a patent that has never been challenged, I mean not successfully. It says that silicon of a higher purity than 99.8% having one or more electrical contacts was covered. Another one with 99.9% is with one or more electrical contacts is covered. It covers transistors, it covers solar vacuum, it covers all this stuff that has anything to do with silicon.

Polkinghorn:

What date was that?

Ohl:

It was issued during the war. Griggs wrote it up. Before I left Holmdel, the Western Electric patent attorney called me up and said, "I just ran into this patent of yours. I just wanted you to know that in my twenty years with the company I have never seen such a broad thing." Well, what good does it do? The societies will not recognize a patent; other literature did not recognize the patent. Only the company as far as salaries were concerned recognized this patent as a publication just like any other publication.

Polkinghorn:

Yes.

### Research on plants

Ohl:

I have some work that I have done recently.

Polkinghorn:

All right. I'll be glad for you to fill me in.

Ohl:

You know this work that has been done about plants. They have a nervous system.

Polkinghorn:

You should love them, yes.

Ohl:

Well, some fellows talked to me about that. I thought this would be a nice thing to look into. So, I looked into the thing. For the most part the plant responses that you record are largely due to natural processes, the presence of an individual. For instance, a dentist came into my laboratory one time, and whenever he went up to the plant that had electrodes on it, it went crazy. So, I said, "Well there is only one thing to do. Would you mind going out into the garage and talking off your shirt?" He did, and then came in. It was just as steady as could be. Noise, you see, affected the thing; it would jitter. At one time I found a earth stamper about two miles away, and it would jiggle every time the thing came along the stamp. Or a vehicle would go by. Finally I set up a microphone. I had these two refined gold electrodes. I refined the gold so that there was no trouble with a nice good steady contact. I played music on it and I could get music through. It was just simply a condenser microphone and I could take a piece of mike and put it in between the electrodes and I could do the same thing. I investigated the leaf and found that the leaf had a hard layer on top and below it was soft. It was like an electrolytic condenser, and I plotted the resistivity and the change in capacitor with resistance. I had written that up but I don't know what to do with it.

Polkinghorn:

I am sure that there are some magazines that would like to have it.

Ohl:

As far as I know, the only thing I couldn't do was that I didn't have lie detection equipment. That measures change in resistivity, but my thing responded to change in resistivity too. I had very high gain on it. I was able to get down in the micro bold region. I used Bell Laboratories techniques in building this equipment.

Polkinghorn:

Science would probably publish it.

Ohl:

Yes.

Polkinghorn:

Thank you very much.