Russell Ohl - Session I

Hoddeson:

This interview with Russell S. Ohl is beginning on August 19, 1976. We’re in Russell’s home in Vista, California. I would like to begin by recording some additional facts about your early, background to supplement the autobiographical manuscript account that you so kindly let me borrow. I have made a copy of that for your file at The American Institute of Physics, so we needn’t repeat what is already recorded there because it will eventually be made available to scholars who will consult the transcript of this interview. You were born in 1898 in Macungie, Pennsylvania. That sounds like a small town.

Ohl:

It is very small.

Hoddeson:

Were your parents natives of Pennsylvania?

Ohl:

Yes.

Hoddeson:

You mention that your father’s education was in the arts and that he was in the lumber business during your childhood. Did he have any scientific interests?

Ohl:

Only as a hobby; astronomy was his hobby.

Hoddeson:

Can you tell me a little bit more about that?

Ohl:

No, because he was almost 40 years old when I came along you see and I was too young then. He abandoned that very shortly after that.

Hoddeson:

Did he have astronomical equipment at home that you had a chance to look at as a child?

Ohl:

Yes. I still have an old telescope.

Hoddeson:

Are you implying that you developed an interest in astronomy as a child?

Ohl:

Nope, I never knew anything about it. Would you like to see the old telescope? Hoddeson I certainly would like to later when we take a break. What was your mother’s background? Well, that is spotty. She actually came from a pioneer family of that era. Her father had some trouble supporting his family because he had some kind of a physical handicap. When she was sixteen or somewhere around there and wanted to go to teachers’ college, he couldn’t send her to school, so instead of that he acquiesced to let her come to a practicing physician in Macungie and she served as assistant to him. That’s where my father met her. After marriage, she wanted a steady income so she prevailed upon my father to give up his artistic endeavors. He painted portraits, landscapes, and did general decorative work. He had painted figures of people on the sidewalks when he was a little boy. It was a natural talent. He could paint with either hand. Once, in our high school, he demonstrated the complicated structure of a bird and drew both of them at the same time! People still remember that. He also helped to organize tile town in which he was brought up. He was a councilman there. He was a leader in the church that, incidentally, my great-grandfather helped to found. And in the town of Robesonia where we moved to, he was president of the council. And he was Sunday School superintendent, and that sort of thing. At one time they prevailed upon him to run for the State Legislature with Theodore Roosevelt, but he didn’t make it because it was a heavily democratic county. That’s a sketchy background.

Hoddeson:

I’m still trying to gain some insight into where your scientific interests might have come from. Both you and one of your brother turned to electrical endeavors fairly early.

Ohl:

Well, I’ve thought about that and I think it’s like this. I think that science is an art and I think it comes from the artistic talents that we had naturally. My older brothers were violinists, but they didn’t follow that because in those days one couldn’t earn a living playing the violin. This was in the early 1900’s when there was no radio and no TV. You’d play in church affairs. They had a small orchestra and townspeople would play in it. So you see that artistic talent runs in the family but was converted into scientific work. My scientific talents depend largely on images; I picture everything in my mind as a picture, not on a piece of paper. I can translate that from my mind by taking wires and putting them together and that’s something most of the engineers could not do.

Hoddeson:

Which of your two older brothers was a telegraph operator? You don’t mention that in the article.

Ohl:

My oldest one, Arthur.

Hoddeson:

And was the work you did as a young child of 5 to 7 on batteries and telegraphs, that you describe in your manuscript, criticized by your brother?

Ohl:

I learned to do it by myself. I did most everything by myself, experimental work. But I watched other people to get information. When I went to college, I studied in the library. I read books and things in order to get the information that I wanted. I went to college with the definite idea not only to get a diploma, but to get an education. I was interested in electricity and chemistry, so I used my time to educate myself and I didn’t give a hoot what kind of grades I got as long as I passed them. So that is the peculiar picture: just a bull-headed Dutchman, that’s all.

Hoddeson:

Your first contact with the idea of wireless came at age 7, as you have described in your manuscript. I was particularly struck by your close contact with the local craftsmen — the blacksmith, the chemist, the watchmaker, the superintendent of the furnace, etc.

Ohl:

Yes, I must have been a nuisance. But you see my father was president of the council and he was pretty well known in town, and I think that is what gave me access to all these places. I was brought up to be careful in my behavior so I didn’t go around fiddling with everything. I just observed and asked questions. And they didn’t mind this; they liked it.

Hoddeson:

The wiring for electricity in .your village around fiddling with everything. I just observed and asked questions. And they didn’t mind this; they liked it. The wiring for electricity in your village around 1907 appears to have been a most crucial influence on you; you describe it so vividly in your memoir.

Ohl:

That didn’t seem to me to be very difficult, I could catch on to the simple process, fast and this got the electrician’s goat. It took him a year or more to learn how to do it. I guess you know how that is. If you learn fairly rapidly you stand out among the others and there’s a certain amount of envious feeling towards you.

Hoddeson:

Yes, sure. It seems that by the time you were 15 you were definitely set upon becoming an engineer, for you entered the Keystone State Normal School in 1913 as a special student.

Ohl:

My teachers always told me in public school that I would do well in research even before I knew what research is. I made experiments in public school that did not occur to the other kids.

Hoddeson:

Did you do these after ordinary school hours? You are talking about the local high school now, I assume.

Ohl:

Yes. They used to give me a lot of leeway. I was very fortunate that way; they were pretty open-minded. If anyone wanted to learn something they’d give you the benefit of the doubt.

Hoddeson:

And did you always work alone?

Ohl:

Not necessarily because I wanted to. There wasn’t anybody else to work with.

Hoddeson:

How good was the equipment?

Ohl:

No good. I had to improvise everything. For instance, when I wanted to find out how much water is in potatoes, after I weighed the slices, I took them down into the basement and put them on a coal shovel which I placed in the furnace very carefully so they didn’t overheat. After that I weighed them to find out how much water had been lost and then when I wanted to find out the total amount of ash in it, I put it on a porcelain plate that I’d scrounged somewhere. I put this in the furnace on the hot coal until I had nothing but ashes left. We had to make pretty nearly everything. We had to make a centrifuge in the high school that we used for testing milk, I remember that. I tested milk for cream content with, sulfuric acid and the centrifuge. We made our own wooden boxes and used to watch the sprouting of beans, in a typical experiment.

Hoddeson:

Tell me about the teachers in your local high school.

Ohl:

My teacher was a farmer’s son. He was educated at Keystone State Normal School. He did summer work at Penn State and finally got to be a county superintendent of schools. But he was very literary minded, and he was a fairly good mathematician, too. He would teach all these subjects and drill us in. them; that’s all I can remember. One time I had a teacher who was a retired mathematics teacher from a normal school. He had put in a year as a public school teacher, a makeshift job.

Hoddeson:

What did the status “special student” at the Keystone Normal School mean?

Ohl:

It meant that you took courses for college credit. Now for instance, I entered that school when I was 15 together with another boy from my high school class. Homer and I went there and we studied solid geometry, trigonometry, college algebra, English literature and English composition. My literature teacher was an editor for the Funk and Wagnall’s dictionary. We studied chemistry, physics, German, and we started to study Spanish but the teacher finally said we ought to give up Spanish as it was too much.

Hoddeson:

Who supported you while you attended the Keystone school?

Ohl:

My father. You know how much that cost for a whole year, boarding and everything else? $325.00.

Hoddeson:

That doesn’t sound like much money now, but in those days…

Ohl:

Oh, that was a lot of money then. Multiply it by 5 or 10.

Hoddeson:

Well, it seems to have paid off, because then you were able to enter Penn State.

Ohl:

There’s something I’d like to tell you that I’ve told a few people: I have had the experience at certain times in my life that I could see into the future and know what would happen. I knew when I was a young boy that I was going to do something that was outstanding in a way. I didn’t know what it was, but it just seemed to me that was what was going to happen. And I seemed to be instinctively guided towards this technical work. Something comes into your mind and you don’t know where it comes from. These are things that you can’t make any sensible description of it all. When I got to college and started getting into radio work, it was as though I had been guided. And, throughout my technical work, whenever I deviated from a certain path my experiments were a terrible flop; just didn’t amount to anything. And when I’d turn back to a certain path of endeavor then everything turned out right. I have had premonitions about a lot of things. Now for instance, when the Nobel Prize was granted, that morning before I woke up, the whole history of that flashed before my mind. Homer Dudley called me up in the morning, and said, “Did you know that Walter Brattain and so forth had won the Nobel Prize?” And I said, “Yes, I’d known about that.” There was also something else that I could never explain in this revelation. It said that they first considered giving my name for the Nobel Prize and then there was some kind of discussion and they finally decided to add these other 3 people, Brattain, Bardeen and Shockley. Finally, they dropped my name. This had nothing to do with a conscious effort; it just flashed into my mind. I had another experience like that in. the ‘20’s. I had a very pressing problem at one time. The problem was to take the radio signals from two antennas and synchronize them. You know what I mean by that? When you synchronize you get the phases alike.

Hoddeson:

Yes.

Ohl:

Well, one night just before I woke up, the whole circuit for doing this without any moving parts flashed into my mind. I went to work that day and in a very short time I had constructed the device. You could take the signal from two antennas, put them on the oscilloscope and get a straight line — you have to hold them in step to do this. I used semiconductors to do it. That was about 1930. Then in 1933 I began to deviate into short waves and that was when Dr. Wilson gave me the opportunity to work on short waves. This was the thought that had come to me when the first World War ended. I was about to step into my testing airplane when the whistles started to blow and it seemed that bedlam let go. I said, “I guess the War is ended. Now what am I going to do?” And right away the answer came: “Do what you can to extend the short wave radio spectrum.” That was to be my objective. Whenever I deviated from that objective, my efforts failed. I never could explain this.

Hoddeson:

I suppose you never will.

Ohl:

I never will. And another thing, I knew that the transistor was to be found; I knew that ahead of time.

Hoddeson:

When did you know that?

Ohl:

I knew that in about 1939. And then in the 1940’s, they decided that I should have a chance at trying to make an amplifier out of silicon. But the bottleneck of the thing was here.

Hoddeson:

Tell me the story!

Ohl:

That’s one of those flashes that I got: I got a flash that I was never going to invent the transistor, the amplifier.

Hoddeson:

In 1939?

Ohl:

Yes, it wasn’t to be me. And in the early ‘40’s Dr. Bown thought that I should be allowed to go ahead and try to make an amplifier and I was bothered with the situation. The situation was such that if I deviated from high frequencies, I’d be kicked out of Holmdel, and that was a very serious thing, because my family was down there and the kids were in high school and everything was settled there and I didn’t want that to happen. I knew that if I went for a transistor developing the N-P junction I would have a low frequency device because I had already measured the capacity of the junction. Actually that’s where Dr. Shockley got his idea. One day he visited me and I demonstrated one of the N-P junctions I had set up, with a light source and a relay. The light excited the photoelectric junction and caused the current to go through the relay and that cut the battery off or on and the light would follow.

Hoddeson:

Now that occurred in ‘45, right after the War? Or was that before the War?

Ohl:

The date I don’t know. But this was a part of that development.

Hoddeson:

In one of Shockley’s articles^[1] he mentions a visit to Holmdel in 1945 when he saw a demonstration arranged by Kelly of an amplifier you had built lacking vacuum tubes. The amplification was derived through the use of point contact detectors.

Ohl:

That’s right. Negative resistances. They acted as negative resistances which is probably due to heating effect that lowered their resistance.

Hoddeson:

Shockley claims that this was very important in setting him on the road to thinking creatively along the lines that eventually led to the transistor. But why did Shockley happen to visit your laboratory then?

Ohl:

Well, Kelly brought them down.

Hoddeson:

Kelly brought down Shockley and whom else?

Ohl:

And Brattain I think.

Hoddeson:

Brattain.

Ohl:

There might have been somebody else. Shockley said to me, “Did you ever think that if you put a point contact at the barrier, that you could then get control of that current flowing through?” And I said to him, “Yes, I have thought of that but I didn’t have the facilities to do it.” I was working with silicon and in order to do that I’d either have to have a proper current source to do it electrically or, preferably, do it with a very fine oxyacetylene flame, and I didn’t have that stuff. In my work I was constantly hampered by lack of funds. I had to get approval through people who didn’t understand what I was doing. And this is tough. You get tired of begging. So I didn’t do it. Well he said, “We’re going to have a lot of facilities in my laboratory.” This was about the time that Kelly decided he was going to set up Shockley and the other two in a laboratory. At first I did experiments for them. For instance, Shockley called me up one day and said, “John Bardeen says you know it ought to be possible to get control of the current in a thin film of semiconductor.” He said, “Do you think you could make a test of that”? “Well,” I said, “I think I could take a stab at it.” And then I rigged up a device in which I tested the thing where I could get a Voltage gradient of about a million in vacuum, and we couldn’t get an effect. So this result went back to them. And Bardeen was said to have reconsidered the whole thing; he said that his conclusion was that the field would not penetrate through the surface of the semiconductor. And after that they were in a position to take over; they began studying that. So again my interest was in pushing to higher frequencies. These N-P junction devices wouldn’t work at high frequencies at all. And in fact, it was borne out by the history of this that only the point contact devices would work at the very high frequencies. We got into the fractional millimeter ranges. Now here’s another very important thing: in the early work we were talking about copper oxide units, and my people and J. A. Becker particularly said that copper oxide units would do everything that a crystal detector would do. I said it won’t, because I’ve had experience with that. So I made tests. We demonstrated to officials of the AT&T company that point contact detectors would hold up at the high frequency end, whereas the copper oxide units, even the best ones that Becker could make, would fall off way before you got there. You know in order to make a simple test there was an enormous amount of work that had to be done. I had to make my own generator. R. O. Grisdale did the first silicon work. Now here’s another thing that is not written about: this cost Becker very heavily. Becker had asked for fabricated silicon rods and discs to make resistivity measurements. The first photovoltaic unit was in his hands, in that department. And he missed it. He didn’t find it. I found it when he returned it to me. I found the barrier. He simply reported that it was too erratic to make measurements on. Mervin Kelly was not pleased that he missed observing the barrier. Because that would have been a feather in the cap of the Murray Hill Laboratories instead of originating at the Holmdel Laboratories. It should never have come from Holmdel, because that was a field radio laboratory, and something like this should never have come from Holmdel. You know I’ve told you about the copper oxide situation and the point contact rectifier. Friis and Becker both said that cooper oxide would do the same thing as a crystal detector, but I had the experience and I knew that the copper oxide wouldn’t work. So we had a division of opinions and we couldn’t get together on it. One day we went up to Becker’s laboratory and Brattain was there. Brattain pointed out that the point contact rectifier was different from the copper oxide evaporated contact rectifier due to the fact that the resistance of the device was proportional to the radius of the point while the capacity was proportional to the square of the radius of the point. So as you apply this to higher and higher frequencies you could reduce the diameter of the point and get a better ratio of capacity to resistance in theory. And that was the key to making it work. Now this was not Brattain’s idea; he found this in a famous text book on electricity and magnetism, Jeans. That was the end of the objection to using the point contact rectifier. After that they let me go ahead with it without any argument.

Hoddeson:

Turning back now to where we left off at the Keystone School; you say in your memoir that you saw your first demonstration of radio at the Keystone School. Is that correct? And if so, do you remember your response to that?

Ohl:

I was the one man in the class who got the professor to set it up. I saw this radio equipment in the laboratory. You see, I was a nosy fellow in scientific things. I used to go down to the laboratory on Saturday afternoon at times like that to see what he had in the show cases, and I saw this wireless equipment. This intrigued me. So I got a hold of the professor and I asked him whether he wouldn’t be willing to demonstrate it to the class. I thought it might be interesting. And he did that. That was the first time I saw a wireless demonstration. The demonstration used a coherer for a detector. Later on I made coherers when I was starting to go into the centimeter region; I used coherers at first to get a response.

Hoddeson:

I see. Then you entered the course of electrochemical engineering at Penn State where you stayed for four years. Why did you choose Penn State?

Ohl:

Well, my boyfriend went to Lehigh, but I discovered that Lehigh had a tuition fee of $400 a semester and I felt that my folks couldn’t very well afford that because they were pretty well advanced in years and I thought that by going to Penn State I could avoid that expense; I’d save about $600 a year.

Hoddeson:

Were there other possibilities?

Ohl:

Oh, I didn’t have any trouble; scholastically I could have chosen any kind of school. I wanted to get the most education I could for the dollar I spent.

Hoddeson:

Did you at Penn State study any aspects of the new atomic theory that was then being developed in physics?

Ohl:

You’ve come to a very interesting point. At Penn State I learned nothing about the new atomic theory. The government had this course in radio that was sponsored by the U.S. Army Signal Corps. They assigned an instructor from the University of Nebraska or Kansas, I think it was Nebraska. His name was J. O. Perrine. He taught us radio communications. (I have a little pamphlet that he published before he died.) He gave us our first introduction to electrons, teaching about vacuum tubes. So when I got back to my major electrochemical class, for instance, where they taught about charges on ions, I said to my professor in electrochemistry, “Well this sounds to me like electronic charges.” And they kind of snickered and thought, “Well it might be so.”

Hoddeson:

They didn’t know anything about it!

Ohl:

But it turns out the Faraday number is very closely related to the electron charge. Oh, hi Rusty… (dog barking) (BREAK)

Hoddeson:

We are resuming after a short break. During the break Russell told me that he lived in the Bronx for awhile, where I grew up. When?

Ohl:

From 1922 to ‘27, on Andrews Avenue.

Hoddeson:

While you worked at AT&T?

Ohl:

Yes. I even served on the jury in the Bronx.

Hoddeson:

Was the Dr. Perrine you just mentioned the same man who later hired you at AT&T?

Ohl:

That’s right.

Hoddeson:

So that in the meantime, he had moved from the Signal Corps…

Ohl:

He was a captain in the Signal Corps at Yale. When the College Park School was broken up, he went to Yale. He was a First Lieutenant at College Park and then he was advanced to a Captain’s rank at Yale. I was sent to what is now Fort Monmouth — it was Camp Vail then — after the war he went to Cornell and took his doctor’s degree and I went to work. I had to go to work. I went to work for the Electric Storage Battery Company and subsequently to the Westinghouse Lamp Company and then to the university of Colorado. And then when I was at the University of Colorado, Perrine got the job of heading up the Personnel Department of the D&R Division of AT&T. When there was an opening for a radio engineer in the equipment department, I was recommended to him and he contacted me and offered me the job.

Hoddeson:

I am still back in your Signal Corps course in college. I was particularly interested in the origin of your silicon semiconductor work during this course. You mention this in your manuscript on page 20. Do you recall it?

Ohl:

Well, now let’s look at it like this. My first silicon detector was made from silicon that was made by a previous class in electrochemistry. I was given a piece of that silicon and an iron wire. We set that up in the fraternity house to try to receive a signal. A fraternity brother who was my roommate at that time, who now lives in Salana Beach, Robert Applegate, knew a little something about radio? We were all students in the fraternity house, in the chemical fraternity, and we wondered whether we were having our legs pulled with this wireless stuff, you see. We kind of didn’t believe it. And so we set this thing up to see if it really worked. It worked right off, so that was the turning point. We heard signals from NAA.

Hoddeson:

Might this have been the source of your later focus on silicon?

Ohl:

No, I worked with silicon tight along. Crystal detectors were used for short periods at different times. Along in the early 20’s there was a reflex receiver built. Do you know what that is? There was a receiver built that used a crystal detector; and they used a radio frequency amplifier tube, and then the output of that tube was put in a crystal detector to get the voice frequency. The voice frequency was then put back into the same tube, thus making the tube act as a voice and radio amplifier and then they took the amplified voice frequency out on a headset. But, I was never really enthusiastic about this receiver because Dr. Lester had told me that he had tried in the worst way to make a vacuum tube do two things at the same time. He said it just won’t do it to any degree of satisfaction. And his opinion of that weighed very heavily with me. So I never got very enthusiastic about that kind of receiver. But the crystal detector, I continued to experiment with. For instance, in 1922, I set up a Barkhausen oscillator, and I didn’t have any means of detection other than a thermocouple for the short wave lengths that we generated. So I resorted to crystal detectors after I burned out most of the Western Electric thermocouples. The crystal detectors worked. One day, Lloyd Espenshied came in to see what I was doing and he was very much interested. Then, in 1923, while I was living at Andrews Avenue, I set up an oscillator that was able to deliver about 75 watts of power at 1-1/3 meters. This was a very short wave length in those days. You see, short wave lengths in those days were talked of in hundreds of meters. And this was a short wave length, a little over a meter. I wanted to make tests with it. I tried many kinds of receiving circuits, with peanut type vacuum tubes and other special vacuum tubes and none of them worked well. So then I got out my old silicon crystal detector and used it. Lo and behold, it was sensitive as the dickens. And I could get reflections from the elevated lines on the West Side. The only way I could cart the receiver around was with Russ’s baby carriage. I loaded that up with receiving equipment and I went all around New York University campus with it. I was getting strong interference patterns from reflections from the elevated line from across the Harlem River on the West Side. There again I began to appreciate the power of the crystal detector, this was the silicon detector. Then we took that detector and that oscillator to a friend’s home in Brooklyn on the flats. We set it up there, getting the power from the house current. And we set up a transmitter with a parabolic reflector and we tested along the beam. We again tried to use vacuum tubes to no avail and had finally to resort to the crystal detector. That worked fine. We went way off with that as far as we could go and got the signals. So that was the experience that I had at that time with the crystal. Then I went into shorter wave work.

Hoddeson:

We’re skipping again. I want to go back to your work in the Army. I was just struck by the decided positive effect that World War I appears to have had on the advancement of your career in radio.

Ohl:

The War really changed things; it changed my career from electrochemistry into radio. When you are in any phase of research, and there’s a big change like that, it really does things. They came from all over the world to visit me in my laboratory to find out the latest in the research results.

Hoddeson:

But now you are discussing World War II, aren’t you?

Ohl:

Yes. That was very hard on my health. In that period, from ‘33 on, everybody, so many people, hundreds of people, would come down to my laboratories and expect to see something new each time. In order to stay in research, you have to be able to produce. So it created quite a challenge and I used to spend most of my time thinking about these things and doing all kinds of out of the way experiments. I think this helped to undermine my health, too. Finally in the end, 1940, no 1939 I guess, I had a very severe nervous breakdown.

Hoddeson:

I read about that.

Ohl:

That was due to poisoning. I suffered from carbon tetrachloride and cyanide. I did experiments with cyanide solutions trying to find a back contact to the semiconductor material. I developed fabrication means for the semiconductor material. That all came from my laboratory. How to fabricate this semiconductor material. I used to send this material to the Kosher Jewel Company in Perth Amboy to have it cut. Finally, I decided to cut it myself after I visited the World’s Fair in Long Island. There I discovered the availability of metal bonded diamond wheels. And I thought then that’s the thing that we could use to set up a silicon cutting facility. I got my technical assistant, Max Brown to set up a cutting machine for me. He was very capable and willing to do anything. He built it for me right there. Now you see, as we digress in this, Lillian, I remember a lot of the things that I had forgotten. And that mixes things up quite a bit.

Hoddeson:

We will be able to unravel it later on if we keep on trying to put dates on the events. The most important task for us right now is to get it down. Let’s go back again to World War I. I was struck by your detailed study of Steinmetz’s treatise in this period, which seems to indicate a certain degree of theoretical direction in your work.

Ohl:

Let me tell you what happened. I was taking a second course in Officers’ Training. I’d already passed the first one successfully and I was just kind of marking time. One day the Captain called me in and told me that four engineers had been requested to do life and service tests of radio telephone and telegraph equipment on airplanes in flight. It happened that they had lost their last engineer during those life and service tests in a crash; he was beheaded. So I was put on this job. And two of the fellows renigged; they wouldn’t fly. So another fellow, Johnson, and I did the flying. Johnson had been working for the Bureau of Standards. But now he and I were fascinated by flying. We were assigned two different airplanes. He did his work on a Jenny D and I did mine on a Jenny H. When we took this Jenny H up, the thing that bothered me was that when we’d come down and examine the plane, these darn sparks, excuse my language, it’s just convenient for more emphasis, had burned holes in the celluloid covering of the plane. The housing of the generator, spark generator, would have a hole about like a silver dollar in the 1/4 in. thick bakelite housing. I thought, this would be very dangerous, to take a plane up that would develop this sort of thing. So I had them set up the plane in a hanger and excite the generator with a local motor drive. Then we powered the thing and the airplane lit up like a Christmas tree. It was St. Elmo’s fire all over the plane. That is when I went to the library and got a hold of Steinmetz’s treaties on insulators, because I wanted to find out if we could not find an insulator that would be free of this St. Elmo’s fire. We could cure the fire at the joints by soldering all the strut wires together. But the insulators had to have another treatment.

Hoddeson:

So you were reading Steinmetz in order to answer a technological question, not to study the theory.

Ohl:

That was why. I made a few calculations from his formulas and decided that we had high losses in the insulator at high voltages. And I then had set up the equipment with porcelain insulators. And lo and behold, all insulator discharges disappeared. That was put in the reports to the Signal Corps.

Hoddeson:

One month after the false armistice was announced in November of 1918, you were relieved from duty and you went off to become a professional engineer. You became assistant to one of the research engineers of an electric storage battery company in Philadelphia.

Ohl:

Yes. Incidentally, that engineer was enamored with Thomas Edison’s daughter and he would visit the Edison home on the weekends. He was considered a good match because his father was headmaster of the Germantown Academy which was than a well known prep school for boys.

Hoddeson:

Is he the man who introduced you to the Edison effect?

Ohl:

Not the effect, the method. Yes, yes, the Edison method. He explained that to me and told me all about it.

Hoddeson:

I am particularly interested in that method, because this seems to have been the method that you later applied very successfully at Bell in the exploration of microwave detecting materials.

Ohl:

That’s right.

Hoddeson:

Well, after nine months you had had enough of batteries and joined the Western Electric Plant.

Ohl:

You know, I got chicken.

Hoddeson:

What happened?

Ohl:

Because we had to handle vitriol. We had to pour it out from carboys into two quart pitchers in order to get electrolyte. I used to think if anything happened to this carboy, if it broke or was dropped all of a sudden, and you got a whole batch of this vitriol all over the place, what would you do to protect yourself? I didn’t like that at all. And the other thing that I didn’t like was that so many people were getting lead poisoning. That didn’t appeal to me for a career for a young man. Now I had had an offer from the Westinghouse Lamp Company after I took this battery job and I would have taken the Westinghouse job if it had come sooner. I then wrote to the Westinghouse Company and they said the job was open, so I told the people at the Electric Storage Battery Company that I would rather change jobs; I’d prefer to do a different kind of work. So I changed jobs. First I learned how to build lamps; I learned how to design them. I made some of the smallest vacuum tubes that were ever made at that time. I made triodes in flashlight bulbs, and I did that work myself, did the glasswork. And then shortly after that I was transferred to the physics department.

Hoddeson:

Now, earlier, you referred to the DeForest vs. Armstrong patent litigation in this period. Could you tell me about this again so it will be on tape?

Ohl:

Before I tell you that, I must digress a little bit. There was Dr. Harvey Renschler of the research laboratory. Incidentally, he was from my part of Pennsylvania, near Berneville. He had devised a vacuum tube with low pressure argon in it. It was operated at a resonant voltage of the argon and it was thought that would be a good place to detect signals with it. So we obtained some of these tubes. We tried detecting signals with them and sure enough, they were good detectors. But then, just for the heck of it, we thought we’d try a crystal detector. We tried the silicon crystal detector and we found it was just as good, if not better, and didn’t require any batteries. That was just before the Armstrong incident.

Hoddeson:

This was in about ‘21?

Ohl:

About ‘20. Then, one day, Ben Shackelford called me into his office and asked me to get together some apparatus for Edwin Armstrong. I got together some physics laboratory rheostats and a few things like that. I was to work the vacuum pumps and furnish the vacuum tubes. They came from the McCandless Division. We got some of the original DeForest audions, set that up on the pumps and Armstrong connected up circuits according to the DeForest patents. Finally we got the pressure just right. The circuits then oscillated. In other words, it established that DeForest’s earlier patents were workable, and Westinghouse rights were not valid.

Hoddeson:

You refer in your memoir to a Colpitts oscillator circuit. Did you know Colpitts at that time?

Ohl:

No, later.

Hoddeson:

That’s what I wanted to know. So then you were attending IRE meetings in that period. Was that common for members of the research staff at Westinghouse?

Ohl:

Yes. We lived fairly close to New York. We’d take the Lackawanna and in about 20 minutes we’d be in New York. Then we’d take the subway, the Hudson Tubes, and go on to the station at 33rd and we’d get off there and walk over to the IRE.

Hoddeson:

What institution was Heising affiliated with at that time?

Ohl:

Western Electric Company, the Laboratories. It seems strange to talk to somebody who knows something about New. York. I guess you can infer from what I say that I actually lived in that area.

Hoddeson:

Then you were laid off in a temporary business, recession in 1921 and ‘22 and attended the University of Colorado, as an instructor in physics and as a graduate student. And at that time you married Ruth.

Ohl:

Before I went out there.

Hoddeson:

Where did you meet Ruth?

Ohl:

You see I had about a month to wait at home before school. Part of that month was vacation time. The Westinghouse Company would shut their plant down for two weeks. They shut it down the first week of August arid I had to be at Colorado about the middle of September. So, I spent this time at home. I had a radio transmitter and I fooled around with that. I dated Ruth for I had known her when she was a little girl about eight years old. We had been more or less acquainted all that time. So we hit it off pretty well. The reason that we were married at that time was that t was going to Colorado and the relatives all thought we should have a wedding before we left. So that is how we got married. We were always compatible. Whenever there were dances we’d always be together. So that was the romance.

Hoddeson:

And then you went to Colorado and there you carried out many more experiments in radio.

Ohl:

Oh, yes.

Hoddeson:

Did you do your research on police radio selectors at this time?

Ohl:

No, not then.

Hoddeson:

When did you do that?

Ohl:

In 1922 at AT&T.

Hoddeson:

Oh, that was later. What did you do in Colorado?

Ohl:

Well, I used to have to build everything. First thing I wanted to do was set up a transmitter. So, I had to build a generator, a 1000 volt DC generator to excite the tubes. I got an old generator around the place and took the windings off and put new windings on, set the whole thing up until I could get 1000 volts out of it. It spit sparks terribly. In order to run the generator, I had to use an old fashioned two-pole DC generator. I drove that with a tungan rectifier. Didn’t know you can drive with a halfwave rectifier, did you? That combination was my motor generator, and that took a lot of building. Then I set up the transmitter, but I didn’t have a license so I did some experiments with a low antenna outdoors. In discussing field effects with Dr. Lester, the head of the department, he pointed out that when close to the antenna, the field seems to be horizontal, and at a distance becomes vertical.

Hoddeson:

Did you ever work much with Maxwell’s equations?

Ohl:

I took radio communication with Dr. Lester and he went through the differential equations with us.

Hoddeson:

Did you work much with mathematics later on? For example, did you sometimes, especially later on at Bell, call upon mathematicians to help you?

Ohl:

Well later, when I got into semiconductor work. I was dependent on myself. But things changed in that period. And you got into these computing machines. When you got into that period, you didn’t compute things by hand.

Hoddeson:

Semiconductor theory depended on quantum mechanics which was applied to solids later on.

Ohl:

Shockley introduced this theory at Bell. I wasn’t trained in it. I had to depend on the old theories. I was trained in electrochemistry. They had theories about how these things behaved and I had to use that, and I used that very successfully. In fact, it wouldn’t have been necessary to use the quantum theory. We could have made the same developments with electrochemical theory.

Hoddeson:

My studies indicate that the quantum theoretical work of Bardeen and others was crucial in the development of the transistor.

Ohl:

I knew Bardeen. He was the only man who could really understand what I was saying. He was talking in quantum terms and we finally agreed that we were talking about the same thing but using different language.

Hoddeson:

He was able to translate between your languages! I would like to get on tape the conflict you must have experienced in 1922 when you were approached by your old friend Dr. Perrine again, who was now at AT&T, just when Lester at Colorado offered you a new contract.

Ohl:

He wanted to renew the contract at a higher salary.

Hoddeson:

How did the higher salary compare with the salary that you were being offered at AT&T?

Ohl:

Less.

Hoddeson:

So there were several reasons for your choice of AT&T?

Ohl:

I knew the cost of living in New York at the time and I was really upset about that because actually I liked teaching. It was nice. And I had good results with my students, I had a peculiar record there. The faculty had a curve of so many people who failed. And my students did not fail. I had a perfect record. My students all passed their examinations. And I didn’t give them the examinations. I got those results because I got the students who were ahead to help the other students, I jollied them along and got them to do their work on time so they had time leftover. Instead of giving them time off, I got them to come inside the classrooms and tutor the others. They liked to do that.

Hoddeson:

I’m not surprised.

Ohl:

In fact, some of them were smarter than I was.

Hoddeson:

What did you teach?

Ohl:

I taught sophomore, junior and senior physics and also graduate electrical measurements. I taught them a course in electrical measurements which I never had at College. I filled in when I was in Boulder and got the necessary education. I got education in radio circuits and I took a very comprehensive course in partial and linear differential equations. The instructor was very good; he had written a book on the subject. That’s how I was later able to formulate my own theories.

Hoddeson:

Let’s go on to AT&T.

Ohl:

O.K. Let’s get off at 195 Broadway.

Hoddeson:

How did you like it there initially?

Ohl:

I was confused and I had a lot of regrets. Sometimes I thought I was some kind of a four-legged quadruped for taking a job like that.

Hoddeson:

Why?

Ohl:

Over there I had a nice respectable job at the university. And then I was suddenly thrown into AT&T and I was sitting in an office with other people. I had had a large room with my own desk in it and nothing but my equipment and everything else at the university, you see. So, I was thrown into this situation.

Hoddeson:

Who were the other people?

Ohl:

Milton Almquist, O. L. Loynes and C. S. Demarest, who was the head of the group. He turned out to be a very nice person, Charles Demarest. Then later on W. H. T. Holden. We had been together in The Signal Corps radio school and at Westinghouse in the same physical laboratory; he finally was put into this office. And then there was a fellow by the name of A. H. Taylor; he finally went to the National Broadcasting Company. Then there was a fellow by the name of Ralph Bonnel. He had been a Captain in the first World War and had been formerly employed by the Western Union Company. Can you think back that far, 1922? That was when Lloyd Espenshied was head of the Transmission Department. You see, Ralph Bown was in between; Bown was the group supervisor. I had known Ralph Bown in the Army. George Southworth was there too and he and he reported to Bown and to Lloyd Espenshied. I used to have to contact with George Southworth because George and my boss Demarest used to ride together on the train to work. George talked to Demarest and Demarest didn’t know enough about radio to understand. Then he’d tell about it and got me to interpret what George had been telling him. So there was just a nice friendly group interchanging of ideas. We interchanged ideas to such an extent that the secretary to Lloyd Espenshied got interested in radio and she used to come up to me and ask how to make radio receivers.

Hoddeson:

Did you relate easily to Southworth and Espenshied?

Ohl:

Yes. George Southworth was more of a theoretical man and he always had to have somebody to do the experimental work for him. He was close to the experimental work. Now Lloyd Espenshied had a bachelor’s degree from Brooklyn Polytech and he was a patent man, he invented things. But he was an administrator and he got his start because he was an excellent telegraph operator. He was the first man to hear the human voice by radio across the Atlantic. He was in the Eiffel Tower. He told me about the first transmitter. Ray Heising was in on that. It was before John Schelling’s time. This was about 1915. They made that up with nothing but 5 watt vacuum tubes and they had a whole bank of them. Until they had about 100 watts of power connected together in a special circuit. I knew the man who did the wiring work, a fellow by the name of Christopher who’d started with the Tele phone Company in Boston. So these contacts went way back. There would be occasions in which he would visit; they would have some sort of a shindig.

Hoddeson:

Like the opening of the transcontinental line?

Ohl:

Yes.

Hoddeson:

Do you feel that the first transmitter of 1915 was as important an event in telephone history as the opening of .the first transcontinental line?

Ohl:

Oh yes. That, you see, showed that you could communicate across the water. It showed it was possible.

Hoddeson:

Now, I want to ask you some general questions about your work in this period. Your work in the period 1922 to 1927 was all based on specific technical problems.

Ohl:

I was pretty much of a free lance operator.

Hoddeson:

Were you assigned to a specific set of questions?

Ohl:

I was assigned to radio. I studied and reported what the situation was, the radio equipment situation. I kept the company knowledgeable with regard to the art. I was free to do anything I wanted. For instance, I and Milton Almquist demonstrated the first radio presidential inauguration broadcast to Judge Gary who was Chairman of the Board of Directors of the United States Steel Corporation at 165 Broadway.

Hoddeson:

So you felt quite free in your work at AT&T right from the beginning?

Ohl:

Yes.

Hoddeson:

And did the other people in your department feel the same way?

Ohl:

No. The other people were tied to their desks.

Hoddeson:

What about Espenshied?

Ohl:

He was the director.

Hoddeson:

Southworth?

Ohl:

Pretty free, but he was in the Transmission Department.

Hoddeson:

Another question on that early period concerns the interactions between the engineers at AT&T and those other institutions. Were there frequent interactions?

Ohl:

Oh, yes. We were trained to be diplomatic with engineers from the other companies because there was always a feeling that because we came from the AT&T Company, they felt obliged to do whatever we told them to do, and then they would resent it. We were trained not to let that happen. When we had to deal with other engineers, we took them out to lunch, paid their taxi fares and treated them as though they were in every way equal. You see, we had to deal with all the associated companies. And we had the power to change a blueprint right on the spot. One can’t do that anymore. We had the power to take a soldering iron and change a wire if we thought that was needed. That we would only do under very necessary circumstances. Then I got the job of attending technical meetings. My supervisor who would report to General Carty was a member of a great many societies like the Franklin Institute and the American Physical Society.

Hoddeson:

Who are you talking about now?

Ohl:

Lyman Moorehouse. He would have me attend these meetings and then expect a written report. It would save him going to the meetings.

Hoddeson:

So there were interactions, but they were somewhat vague.

Ohl:

I didn’t feel the effect of the administration at AT&T Company. It felt more like we were an individual; like we were a person. But they were very careful that new men did not overstep the bounds of propriety and for that reason they preferred to employ engineers, for instance, officers from WWI, who had other training.

Hoddeson:

They knew how to keep a secret?

Ohl:

They knew how to keep a secret and how to use tact.

Hoddeson:

With what specific institutions were you affiliated most often? Westinghouse?

Ohl:

NO. I had contacts at Yale University. We didn’t have very many visitors at the AT&T. I visited them. But when I was with Bell Laboratories, then we mostly stayed at home.

Hoddeson:

How frequently did you attend talks?

Ohl:

It depended on when they were, you know. It might be once in six months. It might be once in two weeks.

Hoddeson:

You began taking out a few patents before you came to AT&T and then when you got to AT&T you began to take out lots of them?

Ohl:

That was in 1924. I have those patents here. There was the copper oxide rectifier. You see, I was interested in that. There is something in that connection that I didn’t mention, that I should have mentioned. The thing that impressed me when I was working with vacuum tubes, when I made these very small miniature tubes n incidentally, they were on exhibit at The Ford Museum in the vacuum tube division. — was the vast difference between the power which was supplied to the vacuum tube and the power of the signal. For that reason I was interested in making vacuum tubes that use less and less power, filamentary power and plate power. I thought then that it would be so nice if we could get something still closer to the signal level of intensity than we had had, so I thought in terms of solid state devices. In fact, I took out a patent in which I controlled (on paper) the electron current in a copper oxide rectifier. This was 1927. Now, don’t over emphasize this because many people had the same thought. Among them was Lee DeForest. He tried his best to make an amplifier out of the solid state. But I had known something that I haven’t mentioned to you. Maybe I mentioned it in that letter. An Army Signal Corps sergeant had told me that he had known a radio operator who operated a carburundum crystal with two contacts. He used a battery on one of the contacts to oscillate and make beat notes with continuous waves in a long wave region. He had to receive transmissions over 10,000 miles and such distances. Then later, M. Curtis showed me an article from an English magazine. It was an issue of “The Electrician” about 1912, in which they described a two contact crystal amplifier which was built by the Russians. They claimed that they had measured ten times amplification with it. The possibilities of an amplifier of this type of transistor had been known for years. But nobody had ever made them with germanium or silicon; you can’t get a patent on that. As I pointed out in my memorandum on patents, you can’t just substitute one element that had similar properties to an element that produced the effect that you have patented and get the same effect. Do I make myself clear on that? It’s very simple. If you find that you can get a thermocouple effect with sodium for example, then a fellow comes along and instead of sodium, claims a similar effect with potassium. He tries to get a patent on that and finds he can’t for it is not an invention.

Hoddeson:

Wasn’t the Russian device patented?

Ohl:

I don’t know. I have tried to get a hold of that article and never could find it. A. K. Curtis died and I don’t know what happened to it.

Hoddeson:

You said “The Electrician,” 1912?

Ohl:

No, I am guessing at the approximate time. It was a magazine about (indicating) that high, and about that wide.

Hoddeson:

Pretty large.

Ohl:

Yes. Maybe it was 1/16 inch thick. It had been printed in about 1912 and it was in an English magazine and it was a translation of a Russian article, in English. The reference to the Russian article was given in that article. So it could be traced back if you could find it. You would have to go to the New York Public Library. That’s the only chance I know of to get it. A. M. Curtis had it. I am awfully sorry I didn’t photograph that reference. You know this invention business is very tricky because so often it has a long history. What you think is a new invention has been invented maybe fifty or sixty years before your time. Now in 1912, a German came very close to discovering the NP junction. He was measuring thermal properties of silicon and found that he got remarkable thermocouple effects when he put the plus and minus together. He had the barrier but he didn’t recognize it. So he never got patent protection. The history of silicon junction properties has been very thoroughly gone into. My patent on the NP junction has stood up for all this time. It’s never been contested in the courts. (Break) You ask me to talk about General Carty. He was a very pompous sort of person. He was always faultlessly dressed. He wore a frock coat and he wore a high collar that was parted in the front and he wore a black tie. And he had a black moustache and black hair and he was very proper. He always used to be scurrying around the place. There was a saying around the place, that if you want to get discharged from the company very rapidly, just show General Carty an experiment that doesn’t work. That was the best recommendation for having to seek another job that you could get. As a result of that, whenever a test was made to demonstrate something to General Carty — I wasn’t at the demonstration because I was running the transmitter, the WBAY transmitter, the broadcast transmitter, we borrowed that transmitter for the purpose ad I operated it — the persons that were at the demonstration, said all three pieces of equipment worked perfectly. When Carty bustled in, for a demonstration, he would have one or two attendants with him. Then somebody would explain t to him and he wouldn’t say much but quietly depart. I used to meet him up in the Patent Department. He went up there and talked to the patent people because they were on the 25th floor and his office was on the 25th floor. And he would talk shop with them, When Dr. Jewett took command of the technical aspect of the Bell Labs, including the Development and Research, a new policy was set in. He believed you could buy technicians who could invent or produce anything that was wanted. But the queer part about it was that he did secretly admit that there were exceptions to that and it didn’t always work. I know from experience and my knowledge of other people that it is a wrong conception, that only in some cases can you buy people to do that sort of work. Original research work cannot be produced that way.

Hoddeson:

Now I have had the conception that Jewett was one of the people who really understood the nature of research and of the creative process.

Ohl:

He did. He was very understanding. But that was the policy of the Laboratories created under his direction. And, as in other things, you can cite a lot of cases and say it’s right and the first thing you do is to run into a case which doesn’t fit. You know how it is. In scientific work, you just have to accept it, and Jewett could accept it. But then he put in Oliver Buckley and he insisted on running the Laboratories like a military organization. He had at one time been a major in the Signal Corps and felt the only way to run it was like a military organization. He thought that he could snap his fingers and have everybody jump. And you know engineers and technical men don’t do that. Because there were a lot of people who do technical work that were superior in talent to him. In fact a lot of people who do technical work would not be caught in an administrative job. They consider that a very undesirable thing. It’s true, some people may not be able to do that.

Hoddeson:

Some technical people turned administration down, Davisson, or example.

Ohl:

Oh, yes. I didn’t know that he did. Karl Jansky reported to me when he first came to the laboratory. But it didn’t take me long to see that he didn’t need any supervision. He was one of these persons who could stand on his own two feet and if you tried to direct a person like that, you ruined his virtues. He becomes useless; he can’t work that way. So, I simply considered that my job was to show him things he could do, where to get things, and how to go about doing it, find his way around the Laboratories. But then Harold Friis got him to do this noise work and Jansky got the full credit for it because his brother was influential in the radio business. And Karl told his brother about it and (don’t publish this, this is confidential) he wrote about the results of his work to his brother and his brother informed the editor of Electronics magazine. The editor of Electronics magazine thought this was a wonderful discovery and should be publicized and he went to Bill Wilson and told Bill Wilson that if Bell Laboratories did not publish this work that he would publish it without any further authority in Electronics. As a result of that, Bill saw to it that it was published and that Karl Jansky was allowed to make a demonstration on radio when it was broadcast. We got the credit for that in astronomy circles, but I notice in H. D. Friis’ obituary, they claimed that Harold Friis discovered it, and that isn’t true.

Hoddeson:

When did you first meet Kelly?

Ohl:

In 1923.

Hoddeson:

In what connection?

Ohl:

I was talking with Bill Wilson, you know, my boss, When I was talking to him, we discussed treatment of vacuum tubes. And he said, I think Kelly ought to hear of this. And he called Kelly in. That was the first time I met Kelly. He had a way of antagonizing people. For instance, one of the men that was senior to me in the Westinghouse Laboratories had worked with him. He worked at Westinghouse because he had a fight with Kelly. He had been working on vacuum tubes and he and Kelly had a fight. It was pretty serious and as a result of this, one of them had to leave the company. He was red haired and he was fiery tempered just like the other one. Another time Kelly had a fight with a carpenter we had at Cliffwood, his name was Hageman. He and I got along fine, because I had been a second lieutenant in the Signal Corps and Hageman had been a warrant officer in the Navy. And those fellows are trained to show respect to4e commissioned officer, so he and I got along just fine. But he couldn’t get along with a lot of other people. His language was rough, and he had handy fists, the kind that a Petty Officer would have in the Navy and he was down there at Holmdel because he and Kelly had a to do in the hall and Hageman knocked Kelly down. So you see, Kelly was a person who caused antagonism. In fact, my supervisor, H. T. Friis, once told me that Kelly had spoken to him and made Friis so mad that if he had had a pistol, he would have shot Kelly dead right on the spot. But later, Kelly changed. And then when Kelly was put in as Director, he was put in with the thought that he was young enough to be controlled. And Ralph Bown and Friis and some of us thought they could control him. And I guess they did to a certain extent, but not entirely. Now when that book on radio during the War was written you see, my supervisors Friis and Bown did not think of introducing the semiconductor into its proper place. But Kelly said “Write a section on this in the book.” So you see this change of heart in Kelly came about just before the second World War. The British had gotten in touch with Kelly; they got the authority to get all my secret information and during that period Kelly changed his attitude. Actually, he changed from being antagonistic to the work to being an ardent supporter of the work. He sponsored the work that led to the semiconductor transistor. He sparked that all. But he didn’t want me to do the work on the transistor; he didn’t want that to come out of Holmdel. And actually I was working towards an amplifier, but my work towards an amplifier was based on making it work at very high frequencies, you see. And as a result I was on the track of something. But I didn’t know what. Then what happened was that the company had, we called it a basic contract, a main chief contract with the Air Force to develop millimeter wave equipment after World War II. Then Friis came to me and asked me if I wouldn’t make the diodes for the contract. You see, we used diodes for generating harmonics for beating oscillators, and used them for detectors. And they were absolutely necessary, or no work could be done. He said, “Would I agree to make these for the work for the contract?” Because the contract wouldn’t be carried out without them. I had to top my research on amplifiers to do this work. But I knew that I was not destined to. find the transistor and I didn’t mind it so much.

Hoddeson:

Do you know when AT&T first became involved in research on copper oxide rectifiers?

Ohl:

It was either ‘22 or ‘23.

Hoddeson:

And did you then get involved too, immediately?

Ohl:

Oh, yes. My boss, Charles Demarest, had attended this Physical Society meeting in Washington. And it appeared to him that the copper oxide rectifier might be useful, but he didn’t know how; he didn’t understand the mechanism of it. And so when he came back, he turned over the project to me. Well, it turned out that the Westinghouse Company had developed what we called a rectox unit, for charging storage batteries. So I went to the purchasing agent and I asked him if he could arrange to get a unit, and he said yes, he thought he could. The company dealt on a purchasing order basis with the Westinghouse Company. And they got these units and in addition, very shortly thereafter, got the disks by themselves, a whole stack of disks. Well, that started the work. And then I of course, was inclined to take it all apart, to see what the heck this was all about. I saw there was a tin contact to the copper oxide. TO me it seemed not to be a very good contact; it inserted resistance. So I took a soft pencil of carbon, and I carbonized the whole top of the copper oxide and then put the tin washer on and by doing that and reassembling I was able to realize a reduction in resistance and an increase in current carrier capacity; it didn’t get so hot. So I changed the copper oxide bridge from a parallel to a series disc assembly. Well, the result was you could get about 3/10 of an ampere steadily at double the DC voltage that you could pass thru a filter, a low pass filter, the output of that low pass filter powered a A—A receiving set. And do you know what that set was? It was a double detection set made with ten tubes, and it was a very sensitive set. It was the ace of the receiving sets for broadcast reception. Lyman Morehouse had one of these sets and his chief objection to the set that he had at home was that it required a storage battery which had to be charged periodically. The storage battery could leak acid, which could be a mess by ruining the floor and the rug. “So,” we said, “Alright we’ll make a current supply set for you.” I made this current supply set and he took it home with him. He was tickled to death with it. He said that really was a big improvement. He got rid of all his storage battery supplies and used this instead. This was a direct current supply from 60 cycles. Now that was the first application of that type that was made. And it later developed into something that went into the telephone plant because we could see that if we could make this in large areas to handle hundreds of amperes, we could then rectify current, directly run it through a filter and put it into the telephone plant without needing the very large storage batteries. We could have cheap power to run the repeaters and various things that had to be run in the plant. So, we wrote letters to the Western Electric Corn pan authorizing them to go ahead with the development. And the man’s name who did the work under Becker, was Siegmon. They learned to make those disks work.

Hoddeson:

So there was really a direct line between the early copper oxide rectifier all the way up to the later work on the transistor.

Ohl:

Oh, yes. And then while I was still making that current supply set, I devised circuits for use in a ringing arrangement that utilized harmonics from these rectifiers. I developed the Fourier series for the output of these harmonic devices, and determined how much you get out of the various harmonics. That was the basis for the second harmonic producing the ringing arrangement. Now that was patented and uses made of it. That was patented in many foreign countries. It was my first patent with the telephone company. Does that answer some of the questions?

Hoddeson:

Yes.

Ohl:

I did more on that work. I ran across an article in a magazine that showed how you could take a copper disk, a Frenchman found this, and treat it in a certain way and make a first grade photocell out of it. I decided to try it. I did this in my apartment in about 1924. I made these disks; I knew something about chemistry. A lot of people didn’t, you see. Being trained as an electrochemist, I could just simply switch from one field to the other without having any difficulty about it. I was familiar with both fields. So I had them turn out these disks in the shop and then I treated them with nitric acid to etch the surfaces, to show the crystal structure and washed them in distilled water. Then I immersed them in 5% sulphuric acid in a dark room and left them there for a few weeks. I took them out of that and put two of them in a sulphuric acid solution. When I aimed some light on one of the disks I got a large current from them, but I could never make use of the property other than that. No one has ever suggested any use for it. Then I wanted to do some experiment work with copper oxide units. I wanted to get a little furnace to do it with. But they turned it down, they wouldn’t allow it. Then, one day when I had the transmitter on the top of Walker Street, I decided to see how good these were at high frequencies. Now this is the knowledge I had before. In other words, I had superior knowledge to the knowledge that Becker had and my supervisor. I tested these copper oxide disks at high frequencies. The copper oxide did not rectify on a wave-length of 7.5 meters. There was no indication of rectification with nominal power. So I increased the power until something happened. I finally got one microampere. And just about that time I heard an explosion in the laboratory. The surface of the rectifier had shattered. You could see that the power was going into the rectifying surface of the copper and it was no longer doing any rectifying. It was probably a dielectric loss. I knew then that it was just useless at those frequencies. The next step was in the laboratories at Holmdel when I learned that the copper oxide rectifiers that were manufactured by the General Electric Company were small; they were only about an eighth of an inch in diameter and they were good at 293 kilo cycles, which was the intermediate frequency we used in double detection receivers. We used G. E. copper oxide rectifiers in bridge form a great deal for DC modulators. I made the first static synchronizing mechanism that used copper oxide bridges. When it became necessary to convince my superior that copper oxide was not a good rectifi6r at high frequencies, I built an oscillator having about a 5 watt output capability. It generated enough voltage to spark across the tuning condenser plates and I applied that voltage to the copper oxide disks. There was no observable rectification. Then I showed that a crystal rectifier would require only a small fraction of that voltage to show copious rectified current.

Hoddeson:

When was this work done?

Ohl:

About 1926. That was the beginning of getting the thinking out of the rut that you could do this rectification work using copper oxide rectifiers.

Hoddeson:

And yet Becker and Brattain continued to explore copper oxide rectifiers?

Ohl:

Well, that was the same rut. Becker said, “I can make you one that will work.” But it didn’t work.

Hoddeson:

Much of this is discussed in your manuscript. Is there anything in particular you wish to add to that, or to emphasize?

Ohl:

Well, only the point that Walter Brattain was the first person to show why the point contact rectifier was different from the copper oxide rectifier. I have always concurred with others who asserted that it pays to be accurate in assigning the credit to people. I have tried to follow that policy. I do not try to retain credit that does not belong to me but belongs to someone else. I prefer to keep it that way. So when Brattain pointed out that the point contact rectifier was different from the copper oxide rectifier (this includes the selenium type), I felt that the superiority of the point contact rectifier at high frequencies was confirmed.

Hoddeson:

You talk in your manuscript about the commercial ship-to-shore work that was done in 1919-1921.

Ohl:

I didn’t do that; the Bell System did that.

Hoddeson:

Sorry, the Bell System.

Ohl:

John Schelling was in on that. Now he went over that manuscript of mine that you have read and corrected everything that applied there. He got that straightened out. And that is correct the way it was stated in the manuscript.

Hoddeson:

Now, on the work relating to the quartz crystal frequency control —

Ohl:

Oh that is very interesting. —

Hoddeson:

You talk about this in your manuscript, also, I’d like to ask a question: Why were crystals not, as you say, much in use at that time?

Ohl:

They weren’t available and only a few people understood how they operated. In fact, I was able to get some patents on circuits that were involved.

Hoddeson:

Did you have trouble getting support for this work?

Ohl:

Well, not so much. You see you didn’t have the material and you didn’t have the knowledge and you couldn’t prove anything. You had to experiment and show it. I really didn’t have any objection to that point. We bought our first quartz crystal from the General Radio Company and it cost $50. It was made by Professor Pierce at Harvard. He made it out of quartz disks. The General Radio Company simply mounted it by placing it in a suitable mounting. That turned out to be a very good frequency control. I used it in some of my amateur transmitters. I had amateur experimental licenses and I probably had the first quartz crystal controlled radio telephone set on the air at short wave length. I remember having used it whenever I talked on the air. I had no trouble. I contacted people all over. They would readily answer my call for they were not accustomed to receiving a stabilized carrier. It just penetrated right through like a sharp instrument would penetrate through a piece of cheese. I had three ways of modulation, we called it ICW. Do you know what that is? Interrupted Continuous Wave. For long distance penetration with weak waves we used continuous waves mostly. I could get through because this carrier was stable. On the receiving end, they could receive a steady tone. But if you had an oscillator that was wobbling, it would just wobble around in the noise of the equipment so that you couldn’t identify the signal. Thus, it penetrated to much greater distances. I have cards from Russia, Germany, Switzerland, Argentina, etc. I had an experimental license and I could transmit on nearly any wavelength. With the crystal that I got from the General Radio Company I transmitted on 33 meters. And that was the wavelength I used when I transmitted test signals to Bermuda. George Southworth went down there by boat, the Queen of Bermuda, which left New York Harbor.

Hoddeson:

That was the first transmission?

Ohl:

This was the second. The first one I didn’t have under control. The first was a successful test but it did not have the quality that the second one had.

Hoddeson:

Also, you transmitted from New York to England. Is that right?

Ohl:

Oh, yes.

Hoddeson:

And also New York Harbor?

Ohl:

The whole New York Harbor. We surveyed that from J66 meters down to 7.5 meters.

Hoddeson:

What specifically did Southworth do?

Ohl:

He did transmission work. He was the inventor of the solid portrayal of the field strength. He had distance in one dimension and field strength in another and then frequency in the third dimension. This gave a solid figure. He wrote a paper on this. He and Clifford Anderson used to work on the very long waves, but he also did it on the short waves. This short wave work was done mostly under the auspices of George Southworth and Lloyd Espenshied, and skipped Ralph Bown.

Hoddeson:

Were other companies besides AT&T doing work of this kind?

Ohl:

There were some companies but not any as active as the telephone company, some foreign companies, Dutch and Germans and Italians.

Hoddeson:

Did you know their research?

Ohl:

No. But I could tell from their signals what they were doing. In those days an experienced man could tell from the kind of signals that you were receiving, how they were sending them. For instance, I could identify a crystal controlled transmitter right away. You’d simply turn on a beating oscillator and listen to it. You could tell whether it was controlled or not. You see, you have to remember that in all high frequency work, the basic tool is the resonant circuit. There are certain fundamental things about the sharpness or resonance as a very determining factor. Now with ordinary coil condenser circuits you can have a sharpness of resonance which usually doesn’t exceed 300. But with crystals I got sharpness or resonance up to 50,000. So you see that if you get crystal control you have a more frequency stable device than you did with the coil and condenser. You had a much better temperature coefficient, because you could build a crystal mounting with temperature compensation in it. I have some patents on that sort of thing. I made some later on that had an air gap in it. It had a glass separator that would expand faster than the quartz crystal. Thus it would move the air gap just enough to compensate for a change in crystal frequency as the temperature changed. This produced temperature stability. So, such devices were used at the time. I don’t know if anybody else has used them. Now, how that came about is like this. I got interested in crystals and got tired of paying the General Radio Company $50 for a crystal. It was too expensive. They wanted more for different wavelengths. I had a talk with Fred Lack. He was in Ray Heising’s group in the Laboratories. Fred said, well he had done a little work on quartz crystals; he had had some dealing with the Master Optical Company in New York. He said he was discontinuing that work and said I’d have to talk with them. So, I went up to see $e Master Optical Company. There was a man by the name of Potter who was a doctor of optometry. The other partner was name Shnackenburger. He was a very nice man. He said that he would be willing to work along with us. He said he had done a little bit of work with piezoelectric quartz, but he didn’t really know anything about it. So I said, “All right, fine. Let’s work together on this.” First thing, I said that. I would like to make some of these quartz crystals myself, just to find out about them, not to be in. competition. In order to find out what were some of the problems, he proceeded to give me all of the abrasives and the necessary quartz to make it. I took them home and I made some quartz crystals and I made them oscillate. Then I went back to him and he made more of them in the shop. It finally came down to this, that I taught him how to test them so they could make some successful units there. I gave him the apparatus with which he could make the tests and he paid for the parts. They appreciated this very much and they wanted to do something for me for that. But I told him, I can’t take anything for this because I am working for the AT&T Company. This has to be done on just an accommodation basis. So Dr. Potter said, “Couldn’t you use a pair of glasses”? I said that I do use glasses sometimes when I drive a car. He said, “Well, come in and I will test you and fix you up with a good pair of glasses.” So he made me a pair of glasses that were out of this world. They were corrected to one tenth of a diopter! They were made out of the finest kind of glass. The sight through the glasses was almost as though they didn’t have any reflection at all. It was just beautiful. I really appreciated those glasses. But I suppose if some enemy had gotten a hold of them and sued me for them, they could have pulled one of those tricks that they pulled on the people in Washington, calling it a bribe. But anyway, some years later, I talked to Dr. Potter. He was then Vice President of the American Optical Company. He said, “You know that business grew to such large proportions that it outgrew our optical work in the factory at New York! We had to establish a new factory and we had 250 employees in the new factory in Jersey City. That was a separate branch.” That was all started through my contact with the company. I could have gotten into that business easy, but when you have a job, it’s kind of like having a position of trust. You can’t violate that. Once you violate that, your integrity in the technical field is ruined. So, I could never see any way of taking advantage of it. So that’s the work that I did with quartz crystals. I have done more than that. One day I went to K. S. Johnson. K. S. Johnson was a filter man. He wrote a book on filters. He was a laboratory man too. He was an authority on filters. Now I wanted a filter to separate the carrier from the side band of intermediate frequency, at 293 kilocycles — that was standard intermediate frequency on the receiver. We discussed the thing and I had very stiff requirements and Johnson said they just couldn’t meet them with coil filters. The best that they could do was use Q’s of 300 and that wouldn’t come anywhere near meeting the requirements. But W. P. Mason was working there and he was just starting on crystal filters; he was designing them. Johnson said that Mason claims that he can make the crystal filters that can do this work. So, I said, alright, let’s order them and ask Mason to make up a crystal filter. And he made up the first crystal filter that was used to separate the narrow bands for radio frequency work. And we got them at Holmdel. This was about 1930.

Hoddeson:

You did a bit of work on piezoelectric oscillators.

Ohl:

Yes, piezoelectric. That was in this quartz crystal work.

Hoddeson:

We are about up to your transfer from AT&T to Ball in 1927. You described this in your paper.

Ohl:

This is how that came about. One day Charles Demarest called me into his office and he said he had some bad news. That was when Jewett took over the D & R Department; General Carty had retired. And he said we have to stop all radio work that is to be done at Bell Laboratories. Well, the upshot of the thing was that I said that we had made an informal agreement with the company, through Perrine, that I was to do radio work. I preferred to stay with radio. He said if I would stay with D&R he would make proper arrangements so that I, could continue to do radio work. But I said, that I would prefer to be transferred to the Bell Laboratories as soon as possible, because I wanted get out of New York City. Both of my children were terribly bowlegged because they weren’t getting proper sunlight and proper conditions in the city. So I went and talked to Bill Wilson about it and I told him why I wanted to be transferred to the Bell Laboratories. He wanted to put me on power vacuum tubes; but I said that I didn’t want to do that. I had had bad luck with power vacuum tubes; I had had some bad shocks from power vacuum tubes and I preferred not to get into that. Then he said it would be all right. I would be transferred to Cliffwood where I could work independently and continue my work in what I was doing. And that is how I got to be transferred to the Bell Laboratories in 1927. That was before the whole department was transferred. I was the only one that was transferred.

Hoddeson:

Oh, I see.

Ohl:

The others came several years later. I had my choice of work there. I continued the work that I was doing.

Hoddeson:

Where was that?

Ohl:

That was near Matawan. Do you know where that is?

Hoddeson:

No.

Ohl:

Do you know where Keyport is? Did you ever heard of Perth Amboy?

Hoddeson:

Yes.

Ohl:

Well, it’s midway between Perth Amboy and Redbank.

Hoddeson:

So, it was pretty far away?

Ohl:

Yes. We all lived in Redbank and we commuted to Keyport.

Hoddeson:

Did you feel isolated working in a field lab or so far away from the New York headquarters?

Ohl:

It was fine. I worked best when I didn’t have interference. Friis learned at an early date that the best way to keep his job was to stay out of my way. He and I didn’t cross paths in any way. We had an understanding. I would not attempt to interfere with his supervision and he would stay out of my experimental things.

Hoddeson:

How about Englund?

Ohl:

Englund was not in charge of personnel. He was in charge of property. Friis had taken the supervisory job away from Englund and Englund was bitter about it. Englund had been on the ship-to-shore work and he had a receiving station in Elberon. He did all of the receiver work. He received longwaves and did field strength measurements. He was a very precise kind of a scientist. He had completed his doctor’s work at the University of Chicago. But for personal reasons, family reasons, he didn’t stay there to receive his doctorate. He preferred to take a job. So he took a job in Virginia teaching geology. I don’t remember how he got to the Laboratories but this was a year before World War I. He got to the Laboratories at the same time that Buckley got his job and Bill Wilson got his job. Englund got into the field laboratory for doing field work in radio. Well it turned out that in 1919, Friis got hired as an aide to Englund. I was offered the same kind of job in 1919 that he took. I didn’t want to work in a field laboratory at that time; I wanted to work in the city. But Friis got that job and he became ambitious and when Englund was away in Mexico making field strength measurements, Friis ingratiated himself with Dr. Nichols in such a way that Dr. Nichols advanced him to a supervisory rank. And when Englund came back from his expedition, he had another man of equal rank in his laboratory. That is how this came about. So there was a constant conflict between those two. I wasn’t going to have anything to do with it. I was going to stay free and I did. I had a Dane for a supervisor and I detested him for 25 years. I never liked these people that wanted everything their own way. He was a dictator. He was well trained and a really good engineer. When he got to be a supervisor, he wanted things done just exactly the way he said. And nobody else could have any ideas. So, he and I found we could only get along separately.

Hoddeson:

Friis refers, in one of his articles, to a period in 1925 when you and he and Edmond Bruce all worked together. He implies that you and Bruce sometimes got on each others’ nerves.

Ohl:

No, I don’t think so. Bruce was somewhat antisocial. He thought he was a very important man because his uncle was an official in Washington; his uncle was an ambassador, I think. And he wouldn’t have anything to do with Laboratory people socially. And this ostracized him pretty well. It didn’t harm any of the Laboratory’s people, but it made him an oddball. He didn’t have many social contacts at all. So he resorted to boating, got himself a sailboat and he enjoyed calculating the angles that he could set his sail in order to do certain things on the Shrewsbury River. But he commuted with us. And during that period that I commuted with him, another man that worked with him was Louis Lowry. Louis Lowry and Ed Bruce used to tell us about the results of their work. And this was very nice because it helps to know what the other fellow was doing. And Bruce had found spots in the sky in which there was radio noise. The result of this was that he was, in my estimation, the first one to recognize star noise, before Jansky. He didn’t use the sharp antennas that Jansky used, and he didn’t scan the sky as thoroughly as Jansky did. He let the earth move around and let the earth’s motion move the sound across the sky. Jansky didn’t do that. He made the antenna go around. He would check the sky in the same spot time after time before he arrived at conclusions. He was really the originator of radio astronomy. So Bruce and Lowry made the first observations. But Friis would never acknowledge them because he was boss.

Hoddeson:

Would Jansky have acknowledged it?

Ohl:

No. You see this was a case where the editor of Electronics moved it over Friis’ head and contacted Jansky directly and short circuited Friis. And Friis didn’t like it. The result of the whole thing when Jansky got his publicity was that his work was cut out. They stopped it. They put him on developing low noise amplifiers.

Hoddeson:

And Jansky’s work?

Ohl:

Friis took it over himself.

Hoddeson:

What did Jansky think about this?

Ohl:

I don’t think he thought it was very important. He was a very modest man and actually his publicity grew and we kind of sympathized with him because he was not well. He had a permanent kidney disease. Nobody tried to take credit from him. We thought he had just a few years to live under any circumstances.

Ohl:

For a time, Jansky worked for us at Cliffwood. He was on the organization chart in my group. But that was just on the chart. Well, then we commuted in the same car and we exchanged ideas extensively. And then there was some trouble about the car pool. Bauman left and Sam Reeve took over. The problem was that Sam Reeve’s wife would drive us up to Cliffwood and use the car for shopping the rest of the day. My wife didn’t like that. She would get jealous. So I settled this and I bought a Chevrolet. Then Jansky agreed to drive the Chevrolet for his transportation share and finally he asked me if I would sell it. I said, “Sure. And you can pay me with the money you earn driving it.” We did that. Then he had a lot of trouble, but we had dealings that way. Finally he bought a house directly in back of mine and lived there for a good may years and we rode together. Finally in 1947, we were both transferred to Southworth’s group — he mentions this — and we did independent work there in his group. Jansky at one time was assigned to make measurements on the first silicon transistor. No one had success in getting transistor action with silicon. I had just found this ionic implantation and I had found surfaces there were suitable for transistor action. Well, Jansky was assigned to make transistor action, which he did and he measured the transistor effectiveness. Later the transistors were sent to Murray Hill to a fellow by the name of Pietenpol. He made some tests on it and he wrote a joint paper with me on it. I had made all the transistors. That was given before an electronics conference, I think at the University of Wisconsin, some place or another. I have the test of that paper. It was not published. You might be interested in finding it sometime. I went on with ionic implantation. Shortly after that, Jansky came into my office and he seemed to be sick. He said, “I’ll have to say good-bye to you. I’m very seriously ill and must go to the hospital.” I knew that and I put my arms around him and I said, “I hope you’ll be able to come back and see us soon.” That was one of the saddest moments of my life. Pretty tough situation. That was the upshot of my relations with Jansky. These things that I am telling you I know from my own knowledge; they are first-hand.

Hoddeson:

Who assigned Jansky to investigate what amounted to star noise?

Ohl:

Friis did. Just before the Depression, the Company took on a lot of people in order to help out the economic system. It didn’t work. Shortly after that, they had to get rid of them. They picked out the ones that they thought were not much of a success in research and laid them off. Mutch was one of the ones laid off. He was on my organization chart. We lost another one who was not as good. I don’t remember his name. He used to spend his weekends with a bag of peanuts standing on the street corner watching the girls go by. I would spend my weekends studying what to do next. When you are in a position like that you have to work out what the other people are going to1do, particularly if they are not research minded. I never had to do that with Archie King. Archie King knew what to do. He was a research man. I never had to do that with Karl Jansky. But Warren Mutch, I had to work that out for him and for this other man.

Hoddeson:

We are in about 1930 now. Two other things also happened at about that time. One was that by this time Cliffwood property seemed too small for receiving work and you all moved down to Holmdel which apparently, according to Friis, was chosen by Englund and himself.

Ohl:

No, Englund chose that property. Friis chose the property near Redbank and that property proved not to be any good at all; it was turned down while the property that Englund chose was acceptable.

Hoddeson:

What were the criteria for accepting such a property?

Ohl:

The criteria were the position, the location, powerline interference, accessibility, costs, size and how much property you could get. Holmdel property was ideal property. It was flat. It didn’t require any grading. The Redbank property was too close to housing power lines and to railroads and all that sort of thing. We wanted a property that was free from electrical disturbance.

Hoddeson:

The laboratory was built of wood, wasn’t it?

Ohl:

Building the laboratory out of wood turned out to be a useless gesture. That was a waste of time because we weren’t doing any more long wavelength work anymore. The Holmdel Laboratory — now this you won’t find in the record — employees were asked to make up tentative plans, not architectural plans, rough plans of the kind of laboratories that we thought should be built. Then Friis and his brother, who was a Danish immigrant, made up a plan. And this plan was a 120 degrees plan. I argued against that because I said that this was unnatural. The reason or it was that when I had been at Boulder I once visited a man who had built a hexagon house. The trouble with the darn thing was you never knew where you were. Your mind is oriented by 90 degrees directions. And if you deviate from that, if you take 60 degrees, the first thing you realize when you go through several, you are lost. The mind doesn’t compensate for it. And that turned out to be the trouble with this building. The plan was accepted by Buckley because it was unique, different. It was Friis’ brother’s plan. We thought it was a poorly conceived plan.

Hoddeson:

Did you know Mason?

Ohl:

A quartz crystal man. Yes, I worked as closely with him. He designed the piezo crystals and I wrote the specifications. And in some cases, I rebuilt them.

Hoddeson:

I would like your reflections on the impact of the Depression. In some cases, researchers I have spoken with used the extra time they had, due to released work time, to study the new quantum physics. You used the extra time to work in your home lab. I wonder, would you have done the same work as you did in your home lab had there not been a Depression?

Ohl:

I wouldn’t have done as much work. In 1933, 1 began making vacuum tubes for shortwave generation. I have some records of that. They were intended to produce short waves. So, I started getting into the short wave region. By 1934 I wrote a final report. At that time I was given the opportunity to go on and investigate the high frequency spectrum towards the centimeter and millimeter range and I was given a free hand. In other words, exploratory work. December 1933, I made a study of valence tables because I had studied the Mosely tables of atomic structures. This involved some quantum theory. I had done this pretty much on my own time. I was trying to get a hold of what was constituting a semiconductor. I found that certain crystal structures were favorable and usually the structures were made up of elements of the fourth group. It was either that or you could have other valences like metals, which had to be balanced by a nonmetal. This went all through the periodic elements. That became evident as a result of studying the periodic arrangement. Well, then came the experiment work. We had available early in the studies copper oxide and iron sulfide contact detectors that Crawford had been using in 1 meter work and he didn’t know what they were. So, I got some and took them apart in my laboratory and analyzed them and found they were iron pyrite. You can put them through certain tests to determine that. And everybody was interested to know what they were. They were made by the Hertzog Company. They were just chips of iron pyrite embedded in rose metal. These were used years ago. Then I made noise measurements — I made a noise device in which I measured thermal noise (Johnson noise). I wanted to find out if they were suitable for us in radio work and so I measured their noise and found out where it came from, whether it was from the back contact or from the front contact. That was the beginning of extensive study on the use of semiconductors for high frequency work.

Hoddeson:

Did you know J. B. Johnson?

Ohl:

Sure, we were friendly. I was not sure that noise would behave at these high frequencies the same way as at low frequencies. We talked a lot at West Street. I talked to him after he had retired. Be got tired of being retired, so he took a job at Edison Laboratory at West Orange or some such place. He was a nice fellow. The upshot of that work was I used some of the iron sulfide and made some crystals. I machined them myself. I had a crude device. This was made with some bearings and a gadget that I had gotten from Axel Jensen when he was in England. I made up a, crude lathe and I made up cylinders on it, ground them by hand. The idea was that I could made up cylinders that I could fabricate in such a form that they could be used at very short wavelengths, like 2 centimeters. They had to be very small so you could place them in the tiny circuits. Incidentally, I still have the first circuit that I made. You might be interested in seeing it. I want to tell you more about something that I touched upon earlier. In investigating the prospects of using high frequencies, I found the prospects of using vacuum tubes were almost nil, because you had to have such close spacing and such high voltage gradients, you would get cold emission and therefore you could not hope to use thermonic devices. You had to use something else. You see, I had made very small tubes that were used as magnetrons. I used tiny platinum cylinders and inserted tungsten filaments to get a magnetron effect with them. But the transit then was too long. I really did a lot of work trying to make thermonic devices work. But finally came to the conclusion that it was useless and I abandoned that effort.

Hoddeson:

I just want to ask you one question about Schelkunoff. He gave a course in electromagnetic theory in Holmdel on the 4th of January of 1935. Do you have any recollections of this course? Was such a course usual?

Ohl:

Well no. We didn’t have many courses like that. There might have been other courses like that given but I doubt it. It was more on Southworth’s work wave guides and so on, dielectrics, vector potentials.

Hoddeson:

When did you begin to employ the Edison method?

Ohl:

I don’t know exactly. I made a mineral survey in 1934 — crystal atomic studies of semiconductors. I obtained a very interesting result. I found that all the semiconductors whose electrical properties were known fell into the cubic lattice structure except two. One was molybdenum sulfide and the other one was carborundum, which also has a cubic structure. I concluded that our best bet was to stick with the cubic structure crystals. Later on we narrowed it down to all the elements with the diamond cubic structure. We needed a theory of how the diodes worked and experiment established the fact that you get a space charge right underneath the point when you have current flowing in one direction and when you have current flowing in the other direction there is very little space charge. So you have an easy current flow and you have a blocked current flow. You can calculate changes in capacity due to the current because you can estimate the current density directly underneath the point. Now the memorandum that I gave you indicates some theories that were involved.

Hoddeson:

We will have to make a copy of that and any other pertinent papers in your files.

Ohl:

We can do that. That may not be available because that was circulated under secret conditions. We didn’t make work reports during the War. I did make secret reports from time to time and I have copies of most of them.

Hoddeson:

I’d love to have copies. Let’s now move on to the discovery of the PN-junction.

Ohl:

Before they were discovered we were already applying for patent protection on the use of high purity silicon.

Hoddeson:

Who?

Ohl:

Well, Mr. Griggs was head of the Patent Department.

Hoddeson:

Who told him to?

Ohl:

Mr. Kelly. Mr. Kelly had a misunderstanding about my work. He thought I wasn’t doing any work and he really made it rough for me but I wasn’t overcome by his antagonism. It just made me kind of boil a little bit inside, so I told him the head of the patent department had been informed of a number of my ideas. I handed them to him. Among them as this high purity silicon idea that was producing good results. The next thing I heard was that the Patent Department got busy and applied for about a half dozen patents on the subject.

Hoddeson:

I’d like now for us to go into two points that we mentioned at dinner. You demonstrated to Bown and then demonstrated to Kelly. Then Kelly called in the research department heads to come and see the PN-junction demonstration. Could you tell me about that in more detail?

Ohl:

The effect is described in an early memorandum. I found the effect on a Friday afternoon and I showed it to Al Beck. He had his office across the hall, and then to Chuck Edwards. And Chuck Edwards is no longer here. All Beck now lives in Florida. He wrote me a nice letter on the subject. He still remembered the demonstration. Somebody got a copy of that letter, I don’t know who it was, somebody who was here got a copy of it; they were very much interested in it. Did you get a copy of Al Beck’s letter?

Hoddeson:

No.

Ohl:

Then Dr. Tebo I guess got it. Maybe John Schelling. He thought it was of value. I took pictures of it; I may have a photographic copy of it. This was a sample of silicon whose resistivity Becker said was not measurable. So I decided to see what the dickens was the matter with it. So I set it up for testing, applying the usual AC voltage. I displayed the current on the oscilloscope and I saw the rectifying properties. I saw a peculiar kind of a loop. That is shown in my notebook, I have copies of that, photostatic copies, I didn’t understand this but I noticed that if I did certain things to it that the loop changed and this was the key. I had it held over water and I thought it was the water vapor that made the change. I tested different things and finally we went to a light, an incandescent light over it and we found that that made a change. I eventually took a neon lamp whose light passed through a chopper and put that on the silicon. I found changes in the characteristics which follow this chop in the light. We knew then that we had something that was light sensitive. Then the following Monday I told Friis about it and Friis couldn’t make anything of it and said you better take this up to Bown and show it to him. So I took it to N.Y. City, up to Bown; and Bown was astute enough to know that here was something that had some importance but he didn’t know what it was. He was, as I told you, a Doctor in Mechanical Engineering; he didn’t understand such things in physics and chemistry. So he said you better show this to Kelly. I went up to Kelly’s office and I showed this to Kelly. He had called Kelly and Kelly told me to come right into the office. I put down the apparatus and showed him the device, I pointed a flashlight beam across the room and got a full—scale reflection on the microammeter, and that stirred his interest. Then I showed him a chunk of silicon with I barrier in it. I shined light on that — any place on it — and I could get an appreciable reflection. We didn’t know anything about light transmission of silicon properties at that time, so he thought this was very interesting saying I think that so and so ought to see this thing.” So he called in Dr. Williams and Rob Burns who is Dr. Williams’ assistant. And then he said, “well, I think Herbert Ives ought to hear about this.” So he called these fellows up and said to drop their work and come on up here and take a look at something. Then all these men gathered in Kelly’s office.

Hoddeson:

How long did it take for all of them to get there?

Ohl:

Oh, just a matter of a few minutes. Yes, he didn’t take no for an answer. He said, Drop it, and come on up here9 And so they all came up here.

Hoddeson:

Who else was there?

Ohl:

Brattain was there. Of course, this is where I made a mistake.

Hoddeson:

Had you already named it the PN-junction?

Ohl:

No, not yet. So, then he asked how it worked. And I said, “Well.” I’m always kind of bashful — I didn’t like to show my ignorance about the subject. I didn’t realize at the time that everybody was ignorant about it and anything is a great deal better than nothing. So Brattain comes up with a tentative explanation. And Kelly was impressed. Then Brattain said that to his knowledge this was the first time that anybody had ever found a photovoltaic effect in elementary material. I have a copy of that, Brattain sent me a statement in his speech.

Hoddeson:

Oh, yes. Brattain has mentioned that in several interviews and articles.

Ohl:

Unfortunately, some people suffered from that. J. A. Becker suffered from that because he had that active silicon in his department, in his hands, and didn’t find it. That is what you are up against in research. You’ve got to watch for things like that, for something unusual. If that happens you have got to learn to recognize it. If you don’t do it you’ll miss the boat completely. Now you see when Brattain found the transistor effect he was smart enough and astute enough to realize what was going on. But Brattain used d.c. amplifiers to portray the characteristic. I furnished him with circuit prints. You see, Brattain didn’t know much about electronic circuits. He had to acquire information. He didn’t hesitate to come down to the Holmdel laboratory to find out how to apply special circuits. When the Shockley, Brattain, Bardeen group was set up, they worked under a company secrecy directive. They were not allowed to tell anyone any of their results. Brattain felt pretty badly about it. He talked to me over the telephone about these things and told me what he dared to tell in confidence you know. But he wasn’t allowed to tell about this transistor effect. It was a good thing for them because if he had given me the slightest indication, I could have gone to a table and set up two points on a certain silicon sample to produce the transistor effect. I had the barriers right there. It was that close. When Brattain showed me the effect when I was up there, Friis and I went up there one time, I told Brattain that he had a really good thing there and that he should stick by it and hang on it and improve it. I knew then that if I wanted to, I could have fought that. But I wouldn’t because I felt that Brattain had honestly made this discovery. And it wouldn’t be right, it would be a very cheap thing for me to try to break in on the thing and supercede the dating of that discovery and I refrained from that. I was very pleased that Brattain had found it. Bown and Friis were so anxious that someone in their department should find this, but my work had been limited to microwaves where amplification was not obtainable. And so, Kelly bustled into my place and he took over right away because he understood what was happening.