[Doc Ewen]
Ewen and Edward Purcell with the 60 foot antenna. (Photo courtesy of Doc Ewen)


[Ewen and the horn antenna, Harvard, 1951]
Ewen and the horn antenna, Harvard, 1951. (Photo courtesy of Doc Ewen)


NATIONAL RADIO ASTRONOMY OBSERVATORY ARCHIVES

Papers of Woodruff T. Sullivan III: Tapes Series

Interview with Harold Irving "Doc" Ewen
At Weston, Massachusetts
August 12, 1979
Interview Time: 2 hours, 10 minutes
Partially transcribed for Sullivan by an employee of Ewen-Knight. Transcript completed by Sierra Smith in 2013

Note: The interview listed below was either transcribed as part of Sullivan's research for his book, Cosmic Noise: A History o Early Radio Astronomy (Cambridge University Press, 2009) or was transcribed in the NRAO Archives by Sierra Smith in 2012-2013. The transcription may have been read and edited for clarity by Sullivan, and may have also been read and edited by the interviewee. Any notes added in the reading/editing process by Sullivan, the interviewee, or others who read the transcript have been included in brackets. If the interview was transcribed for Sullivan, the original typescript of the interview is available in the NRAO Archives. Sullivan's notes about each interview are available on the individual interviewee's Web page. During processing, full names of institutions and people were added in brackets and if especially long the interview was split into parts reflecting the sides of the original audio cassette tapes. We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of the original cassette tapes, and for a 2012 grant from American Institute of Physics, Center for the History of Physics, which funded the work of posting these interviews to the Web.

Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event.

Part 2 | Part 3

Sullivan

August 12, 1979, Iím talking with Harold "Doc" Ewen at his home in western Massachusetts on the early years of 21 cm line but before we get into that can you please tell me what your educational background was, and how it was that you first came into contact with astronomy and what came to be known as radio astronomy?

Ewen

I graduated from Tech High in Ď39 in Springfield [Massachusetts], and went on to American International College as a freshman after deciding not to go to Springfield College and become a muscle man. [Ewen: Refused 4 Year Full Tuition, National Hi-Y Scholarship] Then I went to my sophomore year at Amherst. Actually I was on my way up to UMass and thought I was at UMass when I stopped at Amherst and went in and tried their swimming pool. And it turned out at the time I was swimming with the son of one of the professor in astronomy at Amherst. And he suggested that it was a short walk from the swimming pool to the Deanís office and we became close friends immediately. And the Dean then asked me that typical question, "Why do you want to come to Amherst?" And I told him that I wanted to teach at Amherst and I thought that anyone who was a teacher at Amherst should be also a graduate of Amherst. He said he hadnít heard that one before and based on that answer he offered me a full tuition scholarship at Amherst. So I entered as a sophomore and that went on through the junior year until the war broke out. At that time I elected to accelerate my program in the summer of '42 to graduate then in January of '43. Also at that time pressures were put on the faculty at Amherst to call into... essentially, analytical duty at MIT in the Rad Laboratory. And they lost one of its professors, John Hall, who later became the senior observer at Kitt Peak or director at Kitt Peak. John Hall at that time was at Amherst and when he left, then began a search to find a substitute teacher in the field of astronomy. They located me as a senior and I had at that time, just the prior a couple of months, had decided also to major in astronomy. So I was offered the opportunity at the end of my senior year to teach astronomy as a member of the faculty, and also then finish up in January.

Sullivan

So you fulfilled your wish earlier than you might have thought about teaching at Amherst?

Ewen

As a matter of fact, it was done very cleverly by President King, who called me into his office one day. In the spring of í42, I was just finishing the junior year and reminded me of that answer that Iíd given the Dean. And he said, "Iíve got the note here and Iíve also got the recommendations for you to be placed on the faculty as a senior. So hereís your chance." So thatís how I joined the faculty. One of the problems, of course, was at the commencement, would I walk in with the faculty or my classmates. And I guess the record that was sat was the youngest member of the faculty in the 122 years of the College at the time. But that was my history at Amherst and I stayed on at Amherst for one year as an Assistant Director of the Navy V5 training program. That was important for the occasion primarily of working with a director who was head of the Astronomy Department, Warren Green, also the head of the Astronomy Department. Warren Green and I became very close friends during that year while we were handling the V5 Program but it was historical also from the standpoint that the Navy sent their baseball cadets to Amherst and so I had their students for about six to eight months: Ted Williams, and Johnny Pesky, and Johnny Sain. And I got to know them pretty well and everything Iíd give Ted a tough time on an exam, heíd take me down to the ball cage and explain to me that he knew how to pitch as well. If I would just stand there at the plate, he would throw a few over and see if I could drive them up into the net. So Iíve been a good buddy of Tedís some while and it was handy later because many of my scientific friends are also friends of the baseball thing. And I recall on one occasion where Oppenheimer dropped into the lab at Harvard, we all came to attention, shuddering graduate students, and said, "Iíve got a question for you guys. Whereís Fenway Park?" So that was the sort of thing that was very good there. Now from there, we go from Amherst then into World War II with the Navy training in radar electronics, Princeton, MIT. Then off to air training in Florida and Chincoteague, Virginia, and ultimately to join a Patrol Bombing Squadron 112, which was at that time located in England. It had moved up from Africa. And so during that period when I was with the Patrol Bombing Squadron, my assignment as a Radar Officer flying with the squardron, was to fly with the eighteen aircraft, patrolling the English Channel. So we spent a fair amount of time off the Netherlands, and France, and Germany looking for submarines at fairly low altitude in a Liberator type aircraft. It was coincidently about the same time that [Hendrik C.] van de Hulst was giving his presentation in the Netherlands on the 21 cm line and also the foundation of all of the lines that would be forthcoming in the historical development of radio astronomy.

Sullivan

So, you were by the end of the war then very familiar with radar both technically and operationally?

Ewen

Yes. I came back from the Navy, from my last post in Washington, to Harvard to enter the graduate school for a doctorate in physics, which I had selection primarily because the interested in the atomic bomb as a benefactor of my being able to return from anywhere, since I was presumably to go from Whidbey Island to Attu. That had been explain to all naval air types, that the weather conditions on Attu were such that you took off and had a choice of landing in Russia or China after you bombed northern Japan. It was a one flight per shot and you had trained for two months for your one flight. It was in that period that we heard about Hiroshima and Nagasaki and it changed my thinking about my future education, other than finding out what these fellows had uncorked back at the labs in Cambridge. So I then did apply, as a matter of fact, with the Office of Research and Inventions, which became ONR. I had selected a position there as a personnel officer, in the office of personnel, just relocating officers here and there, rather than work as a so-called electronics expert for a patent attorney. And when the time came for filling out applications for the future, Professor Warren Green, again from Amherst who was quite disgusted with my interest in business and law and things like that that I chatted with him about, sent me an application for an NRC fellowship in physics because I told him, "I was now interested in physics but not astronomy." And so he sent me the application, I filled it out, sent it in, and that upset ONR because their physics department, astronomy department- research, there was only one NRC fellow and he happened to be in administration that year. So with my NRC fellowship under my arm, I went off to Harvard to study physics.

Sullivan

This was í46?

Ewen

This was in í46, the fall of í46. And the initial time at Harvard was spent getting the necessary courses out the way. My problem primarily was that I was short in the study of physics. I had not had a good background in classical physics, because my work at Amherst had been predominantly mathematics and then briefly astronomy and only then the application of mathematics to astronomy. So fellows like Newton and so forth were not that well known to me. And it became an interesting game at Harvard during those early years, Ď46-Ď48, that I found it easier to understand relativistic theory and quantum mechanics than understand how I could make N larger and agree with those fellows that liked to bounce apples off heads. So I became known fairly shortly as the "quantum baby". If you take a fellow right out of the womb and put him into graduate school and teach him relativity, he will say, "What else is there?" And it was just so natural and so, but I would occasionally stumble given a problem in classical physics. I had very little difficult with the quantum mechanism and standard thermo and so on.

During that period because of the Navy policy, I was retained as a naval officer on inactive duty. But I would put on my "blue suit" and run down to the Squantum Naval Air Base or to the Fargo building to meet with the Harvard Group, as it was called, of reserve officers every couple of weeks. Our CO at the time was Donald Menzel who during the war was a four striper [Navy Captain] and after the war, he was elevated to Rear Admiral. So problem then was how we could do something productive that would relate to Menzel's interest in the sun, our interest in whatever we were studying at the graduate schools in the local area, Harvard and MIT. And I came up with the thought of building a solar radio telescope since that seemed to be in Menzel's area of interest and it happened to be something that I didn't think would be at all that difficult from what I had heard concerning solar signals.

Sullivan

Where had you heard about this?

Ewen

I learned about the detection through Menzel when he gave a talk at the Reserve Officer meetings. And by then, in preparation for the Menzel seemed mildly interested in this and said, "What do you really know about the field of radio astronomy? Itís come a fairly long way. Are you familiar with Grote Reber and all?" And I didnít know anything. So he said, "Why donít you spent your two weeks of active duty at the [Sterling Labs?] with Grote Reber and Iíll make the arrangements." So, Don Menzel made the arrangements for me to go down and spend a couple of weeks with Reber, which were very productive in understanding of how far away to stop a Model- I canít recall, a Model type car I had at the time. It wasnít the Model A I had at Amherst. But Reber was quite concerned with ignition noise and things like that. It became quite a buzz word in the whole field. So you usually walked into Reberís "camp" from quite a distance. So I spent a couple of weeks with Grote Reber and became somewhat fascinated with what he was doing.

Sullivan

What were your impressions of him at that time? Can you remember?

Ewen

My impression was that he seemed to be- either considered me as though a grad student. I think it did help a little in his opinion of me that I ultimately made arrangements for the Navy to wear civilian clothes rather than the uniform. The uniform he found very appalling and he would not talk to me and he just said, "Thatís stupid. Take that off." So I finally [?] upon the Navy and they said, "Yes. If you are working up there in the woods with Grote Reber, that is fine." And then he would talk to me a little but I had the impression that he was racing against time. He seemed to be overwhelmed with an important task to be completed, which he alone understood. And he was not in a position to describe in detail what the plan would be even for the two week period other than, "Follow me. Pick up that screwdriver. Hold this meter. Do that." And I felt like a real "gopher running around, trying to catch on to what was going on in his mind and why he seemed so desperately anxious to consume every minute. He was always there bright and early in the morning. He worked late. Forget about meals. He was just an around-the-clock, not a [gadgeteer?] at all, just fellow trying to get his job done. It was a very motivating experience. I think became friends to the degree, at the time of parting, of sort of going to a summer camp experience, sort of a mild respect not knowing each other well enough, but understanding the space that surrounded both of us. I recall his saying goodbye and I had to come up and see him in my uniform because I was leaving to go to good old Boston and he said: "You try to get out of that as soon as you can." At least he talked to me for the first time in uniform.

Sullivan

What was he doing scientifically at that time?

Ewen

Primarily, at that time as I recall, his main interest was solar. Though I talked him about a year ago, he said that at that time was trying to get a better feeling for improvement in receiver technology. He had a number of WŁrzberg antennas there, and there were certain obvious things that he felt could be done, and he hadn't discussed them in detail with the Bureau [the National Bureau of Standards, NBS]. As a matter of fact it was about that time, I think it was within a week or two after I left to give you a feeling for what was on his mind, that he disappeared and they tried to send him the famous check that came back [Sullivan: because Reber took off so suddenly and left no forwarding address]. Then finally, some months later he showed up at Maui.

Sullivan

I hadnít heard the famous check story.

Ewen

He just didnít show up and no one knew where he was and the checks came back.

Sullivan

His paychecks?

Ewen

Paychecks. They were just coming about to the Bureau. Where is he? So it got to be, "Has any one seen Grote Reber?" And then about six, seven months later, somebody saw him with a bucket of bamboo on top of Maui. And then he disappeared from Maui and showed up in Tasmania. So he has these moments. And I happened then to see him at the Bureau just prior- an interruption on his way to Maui. But I must say, I don't feel that he has really changed all that much. Just in the last year when I saw him, he was the same exciting fellow, eager to learn and so intense.

Sullivan

That's why I was interested in your reaction. At that time- well hold it now - we're talking about '48-'49?

Ewen

We're talking about '47- maybe, about in there. I was in the Reserve. I left the Reserve in '48, I believe.

Sullivan

Are you getting mixed up with another visit with him as far as him taking off? I think he stayed at NBS for a few more years, until '51 or '52.

Ewen

He went before I left Harvard, I know that.

Sullivan

Yes. That's true.

Ewen

I really wasn't in that close touch with him. I guess it's probably a little difficult when you're a grad student, because I wasn't in that close touch with radio astronomy.

Sullivan

In any case, what I was going to ask you about was his interest in detecting the 21 centimeter line. In fact, he has pictures of his equipment that he was putting together in the late Ď40s.

Ewen

His comment on that, as a matter of fact last year, was that he took a look at it, and he was going to try for it, but he was pretty sure that it was going to be so difficult from a radio standpoint, that it probably wouldn't be worth the engineering effort and I agree with him.

Sullivan

But did you talk to him at that time at all about...

Ewen

About 21, no, because it hadn't entered my life at that time. His interests, as I recall, were primarily solar, and galactic mapping of course, but we didn't talk about any line work. And then as you will recall, to put it in context, during that period and right up to '49, my interest in radio astronomy was equivalent, or motivated, or whatever, by the requirement that I report to the Navy one night every two weeks. So, one night every two weeks I would get interested in radio astronomy with my "Rear Admiral", and we would talk about the sun and other good things out there. Then I'd disappear for two weeks and go back and do something important like nuclear physics.

Sullivan

How long did this go on?

Ewen

Oh, this went on until '49. In '48 I decided to take a position at the Nuclear Cyclotron Lab and went down to Washington and chatted with the administrators at NRC [the National Research Council] because you are not supposed to work while you're a graduate student. So we negotiated and I elected to give up the fellowship [Sullivan: and his Naval Reserve position also?] and proceeded to work at the Nuclear Lab.

Sullivan

What's the official name of that lab?

Ewen

It was called the Nuclear Cyclotron Laboratory.

Sullivan

So, this was a 50 inch cyclotron?

Ewen

A 95 inch.

Sullivan

A 95 inch cyclotron that was being built at Harvard at that time.

Ewen

And we completed it in '49 and wrote it up in 1950. Then I actually went to work experimentally- carrying out experiments. My assignment was to obtain an external beam. Another contribution I meas was details on frequency modulation of the cyclotron itself, moving the capacitive or variable portion of the circuit outside of the magnetic field. During that period I had completed my masterís work, I had completed my course work, and Iíd become quite fascinated with the field of nuclear physics, and this great gadget, the cyclotron. And it was time then to seriously think about a doctorate thesis. Of all the teachers that I had encountered, the one I found most fascinating was Ed [Edward Mills] Purcell and that was through a course in electron ballistics because I had just a slight feeling for electronics from the Navy. A crash program of 90 days at MIT is good, but not an EE [electrical engineering] degree. And then through the experience with Purcell of taking a ride on an electron through a magnetic field and discovering that you are dealing with just about any type of electronic device in a very simple way. It was such a pleasure, very much like his current book where you take a "relativistic ride". So, I found a sort of companionship or sincere interest in his way of looking at things. So I then selected him as my thesis advisor without a thesis and we agreed to sit down and think about thesis subjects. My suggestion package was that it would be helpful to me if I could take the various areas of application, focus them in one direction. There was the radar work Iíd done, astronomy, math, because Ed asked, "Well, what are you proficient in?" And I told him that I had just a smattering of knowledge of a number of "mountains" and I felt pretty comfortable in the "valleys", and I notice that there are a lot of fellows on one "mountain" that donít talk to others and if I could just play in that game. I said in just working with a group in the Naval Reserve, Menzelís group, that by the time I knew a little bit more about quantum mechanics and related that to the astronomical observations, I could see the dichotomy of the radio astronomer from the astronomy end of it, and the electronics engineer, and that they werenít really talking on the same wavelength.

I thought that perhaps there was a place in the valley to bring all this together. And I thought a very interesting one would be to do a bang-up job on the [22 GHz] water vapor line, because I taught meteorology while I was at Amherst. And I had taken while I was at Harvard- Harvard had a requirement in the Physics Department, that you become, in effect, a master of four subjects. Thatís one of their Physics Department requirements. You could satisfy two by courses, you could satisfy a third by taking an oral examination at a master's level and the fourth would be your doctorate field. And at first with some amazement, I didnít realize that there were four separate fields of physics that you could get involved in but apparently Harvard had that approach to it. And so I picked math which was accepted and quantum physics and then elected to take meteorology as a third subject and it required the permission of my thesis advisor. I talked to Ed about it and he said, "Thatís a pseudo-science, not a science - We don't even teach it here." I said, "They teach it down at MIT, and I've been taking courses down there and I haven't decided yet, but I'm so close to completing all courses in meteorology at MIT that I may elect to take a doctorate in meteorology. I think it is sort of a science, if we can separate the various parts of meteorology, the understanding of circulations, and things like that - it's certainly physics of some sort." That was before aerodynamics was a popular thing. Harvard at the time had the [?] Observatory and Professor Brooks and that was Harvardís total part of the program, as a contribution to meteorology.

Sullivan

So you were actually thinking about being a doctor in meteorology?

Ewen

I really didn't know what I wanted to do.

Sullivan

But that a distinct possibility?

Ewen

Right because I taught meteorology at Amherst, but that was when I was one chapter ahead of the students, and I thought it would be really nice to know a little more about it. And so I did then during that period take the courses at MIT, during í47, Ď8, and so on for a doctorate. So then my oral was in the area of meteorology.

Sullivan

What were you thinking of doing with the water vapor line?

Ewen

My interest there was really to get a better feeling for the variability in water vapor, since what [Robert H.] Dicke had done was to demonstrate a technique, but he did not have the opportunity to milk the science that might be there.

Sullivan

Then he didn't get much information on the atmosphere?

Ewen

That's true. And so with the meteorology, and with this electronic technique, it seemed to marry a few disciplines and it also marrying Dicke to Purcell which I found interesting. When I first looked up Dicke's paper and found Purcell's Ok [Sullivan: authorizing] signature on it, that helped a little in focusing my attention on the water line at 22 [GHz]. So I suggested that to Purcell and he didnít seem to be too enthusiastic about the idea. He said, "It would just be another point on a curve that had been done." It could be done. He wasn't refusing me the opportunity, but that it might take a considerable amount of time to measure the line structure in adequate detail to represent a useful thesis.A couple of weeks later when we were still thrashing around from a program, I was over at his house and he said, "I know you are interested in that Dicke thing but it occurs to me..."

Sullivan

Why donít you just finish this story.

Ewen

He said, "A fellow, I think heís Dutch, Iím not sure, but I saw a paper the other day or an abstract where a fellow has apparently come up with a prediction that you can measure the hydrogen hyperfine line."

Sullivan

In interstellar space?

Ewen

In interstellar space and he said, "You ought to look into that," and I said, "Heís from where?" He said, "Well, heís a Dutchman I think, and I saw it somewhere." He said, "I read so many doggone things that come across my desk but I thought of you when I saw it because thatís got to be a lot better than doing a water line in the atmosphere." And I said, "Well, whatís the probability that it can be detected and why doesnít he do it, why doesnít this Dutchman do it?" And he said, "Well, I donít know. Those are things that you need to look into," and he said, "But Iíll tell you, if you can get a gas line in interstellar space, anything like that, not the atmosphere. But if you can get that, youíd get your face in Life Magazine and no one would ever forget you." And he said, "That would be a real great point on the curve and if you donít, youíve only wasted a couple years of your life." He said, "You're the kind of guy who likes to do different kinds of things. Why don't you do this thing? Give it a whirl." And that was his pitch. "What have you got to lose? Just a couple of years."

Sullivan

What year would this be?

Ewen

I would say the fall of '49.

[Lunch Break]

Sullivan

So, continuing after lunch now. So having heard this, apparently you had some interest and then what did you do, how did you proceed with the problem?

Ewen

I did a typical literature search, located a copy of van de Hulst's paper, and arranged to have it transcribe by Purcell's wife, Beth, who was studying Japanese and Russian at the time, and was capable of transcribe just about anything.

Sullivan

Translate you mean.

Ewen

Translate. Translate. We had that in hand and, then as part of the so-called literature search, I began going around to the various club meetings of astronomers, the American Astronomical Society [AAS], etc, and also discovered that Commission V of URSI [International Union of Radio Science] was far more popular from a radio astronomer's standpoint because in the astronomy field, the optical astronomers considered radio astronomers essentially as second-class citizens. And Commission V of URSI was the first receptive international or even national audience. It wasnít that it was international, that wasnít at all important. There just was no place for radio astronomers to go to publish and discuss things.

Sullivan

So, you were going to URSI meetings while you were doing your thesis work before '51?

Ewen

No, this was in early '49. This was shortly after finishing off the oral [Sullivan: exam] in meteorology, and the course studies, and so forth. Looking into this essentially in the direction of Purcell to find out more about the Dutch paper and also about the field and just get a feel for it.

Sullivan

What I'm getting at is that you did get into radio astronomy before 1951. It wasn't until '51 that you began finding out about American astronomers?

Ewen

Oh no. Not at all. I had done quite a bit of reading and had become familiar with Reber's work.

Sullivan

And NRLís work?

Ewen

Absolutely.

Sullivan

Now, did you get any useful advice, during these couple of years before '51, about radiometers or astronomy, as far as that goes?

Ewen

None at all. As a matter of fact, I was pretty much alone as far as the radio astronomy part of it was concerned, because there was no activity at Harvard in that area, nor at MIT to my knowledge. So I would depart from this community of Cambridge scholars, so called, and then go off to these meetings and come back to report, "There are people out there working in this field." And so, nor did I make any close allies or friends in the field at these meetings because they were rather short with me. Though I did get one occasion to chat with John Hagen, who is a Boston-type, who was at NRL at the time. And I recall leaning over at some meeting, it was down at Yale, Commission V URSI, and I tapped him on the shoulder and said, "Iím Doc Ewen and Iím from Harvard and I was wondering where, when you are speaking later this afternoon, could you talk about this 21 cm line that has been suggested by van de Hulst because Iím going to be detecting it for my doctorate thesis." And he turned around, with a look on his face like, "Go home. You donít even belong to the radio astronomy club." And just sort of, "Well, thatís very interesting but we do have other things on the schedule this afternoon." [Ewen: Suggest deletion of statement out of context, given the situation] And so that just went down the drain. So I went back home. I thought that was a loss, to get to know all these fellows. Of course, most of the publications were Australian or...

Sullivan

England, yeah.

Ewen

So from that, I then went back and chatted with Ed Purcell about carrying out this experiment and my feeling was that in reviewing the literature was that the Russians really were likely to detect it long before we could get the equipment together. And that was based on Shklovsky's paper.

Sullivan

His í48 paper, yeah.

Ewen

Right, which was so close on to the time I became involved in looking into things. And it was about the time Iíd read van de Hulst and Shklosky and Iíd talked to what few in the U.S. who were doing anything in radio astronomy, and it seemed to be one, a difficult experiment, a very risk doctorate type thing since there was considerable questions as to what mechanism we might be dealing with here, or if there was anything we would be dealing with. And so Purcell so then sort of summed it up, since he couldnít really justify it logically- go to the blackboard and say, "Well, hereís what we..." He justified doing it simply by saying if you can do it then youíll be in Life Magazine, youíll never be forgotten and if you donít do it, itís only going to cost you a couple of years of your life. And I said, "Fine. On that basis, since we understand each other, Iíll go back and get a better job at the Nuclear Lab for the long pull and weíll continue to look into this in sort of a hobby way in the interim. Why donít I take a little harder look at what we know about the hyperfine line because it would be awfully nice to know what frequency very precisely I should build this device on." And that wasnít a very simple thing to come by in those days.

Sullivan

Well in fact the frequency you were using was measured by Kusch and Purcell.

Ewen

Kusch at Columbia [Sullivan: 1950 publication] and that was the one we used.

Sullivan

Right. But was that experiment done because of your need for a precise frequency or it just happened it was done at the same time?

Ewen

It just happened. It also just happened coincidently that [W. W.] Mumford came up with the gas discharge noise source as a method for measuring the noise figure of microwave receivers just at that time, and that's why I built a gas discharge noise source to calibrate. Ed and I agreed that if we were going to do it, let's do it very right. I think a lot of the care to make sure that it was done right was jointly shared because both of us felt very optimistic when we met, but perhaps a bit pessimistic when we were alone and you want to make sure when you come up with a negative thesis, it is very important that you, for example, have an antenna that you know a lot about. So you think about a horn antenna. It's pretty simple and is well described in the "Rad Lab Series". Although it might have been easier and quicker to throw together a parabola with a feed-at-focus, slot fed British dipole, that was rejected immediately by both of us.

I was really quite pleased in the discussions I had with Ed when I would say, "Why donít we do this?" or heíd make a similar suggestion, weíd both agree and invariably it was related to making sure that when we said it hadnít been detected, we knew how far we had gone, how precisely. In other words how much more difficult the task to go beyond the "point".

Sullivan

Or as we would say now, you wanted to make sure you knew what your brightness temperature limit was.

Ewen

Right. We wanted to able to say that this transition is not detectable in interstellar space above this level.

Sullivan

Were you worried about interference?

Ewen

No. Not at all.

Sullivan

At those frequencies in those days, I guess it wasn't too bad.

Ewen

1420 was a very high frequency in those days. Though X band was around, things like that, radar. There wasnít that much activity going on.

So, we agreed to proceed and that agreement was put into effect in the spring of '49. Decisions then about methods were the point of discussions we had. And I think of the basic decisions were made at one meeting early on. That the antenna would be a horn. That calibration would be by a gas discharge noise source. That the mixer would be a scaled waveguide mixer, based on a drawing in the "Rad. Lab. Series" that had been drawn and placed there by Bob Pound, who was right next door to Purcell's. So if I couldn't understand how you scale that drawing, I could ask Bob. And that we would use a 1N21 crystal, which was a pet also of Bell Laboratories and coincidentally, the crystals were provided by [Harald T.] Friis at Holmdel, at a meeting I had down there drop in at Bell and make sure that I had not overlooked anything in microwaves and putting this receiver together. So the care was just to make sure that we were doing the very best in the state-of-the-art, calibration was appropriate. I recall the afternoon I was ushered into Friis's office, just prior to leaving to go back to Boston. He reached down into a drawer in his desk and said, "I've been waiting for an occasion like this to give some kid the very best crystals Iíve ever seen, the 1N21 crystals. These are beautiful." As a result, I had two of the best crystals from Bell Labs and the Director sent me back on my way to Boston.

And then the Cascode circuit for the preamplifier was a critical item. I then contacted Bill Prichard, who was the Radar Division Manager for Raytheon in Wayland at the time, to determine the status of Cascode or better preamplifiers, developed by Raytheon in their radar effort during the war. He provided me considerable insight on the Cascode amplifier plus some very nice tubes and the latest circuit designs. And Bill, since that time, has went on to become Director of COMSAT and so on. We have kept in close touch over the years, but that's how I first met him was getting into the preamp game through Raytheon. That's why he is mentioned in my thesis. So, that put all the parts together, and from there on in, it was just a matter of gathering together the test equipment and assembling it.

Sullivan

Were these low noise components essential in detecting the line or did they just give you a much better signal-to-noise?

Ewen

The parts that I actually fabricated - designed and fabricated - were the horn, all the waveguide through the mixer, which including a slotted-line prior to the mixer, the gas discharge noise source in full L-Band guide, and all of this was done to be absolutely certain of the calibration more than anything else. For detection, no. [Sullivan: meaning, so much care was not required for merely a detection] I would think, for example, today you could detect 21 centimeters with the electronics in a pack of cigarettes, and a paper clip.

Sullivan

But you could of then also, but you didn't know...

Ewen

But I think I would have been a little reticent though, for example, to place a number on the brightness temperature to the degree I was happy to do then. We were dealing with new techniques at the time but certainly just the idea of what we really mean by antenna beam efficiency for a feed-at-focus parabola is still pretty much out-to-lunch with most electrical engineers even today.

Sullivan

It's not a standard concept.

Ewen

Right. They don't think in that term and Iíve counted numerous problems in that area, just currently. Itís still not put to bed correctly. In answer to your question we took the care to put something together so that, in the words of Purcell, "Faced with a 'wet rock' we will make it as dry as possible." So weíve got to say this canít be detected. So that was the care. Now second, you should keep in mind it hadnít been detected and its presence was very suspect. Even when we did detect it, jumping a little ahead in the story, there was considerable analytical flap over what we detected. We detected hydrogen and we knew we had detected the hyperfine line. Just why it was there and why it had that intensity got to be quite a bit of discussion.

Sullivan

And Ed Purcell told me about some of those questions but let's go back. Another critical aspect was the whole business of what bandwidth and what kind of switching to use. Can you tell me about those decisions?

Ewen

With regard to bandwidth, the thought was that the minimum bandwidth should be somewhere around 5 kHz. This was selected on the basis of considering what spreading there might be caused because of the antenna beam. Not much thought though really about a fully thought out analysis of what we were going to face with the motion of the Earth and the Solar System, that came much later, as a surprise. So, originally it was somewhere in the 5 to 20 kHz bandwidth would be adequate, certainly not less than 5. Second and this in part influence by the fact for a typical AM receiver 4 to 5 kHz is a reasonably easy bandwidth and 20 to 30 gets to be pretty hard to come by unless you are going to modify the receiver. And I decided that all of the processing part, the IF strip, would be an off-the-shelf [Ewen: 30 MHz] communications receiver [Sullivan: National Radio], where you could plug in variable bandwidths and do all that sort of thing. Why discover radio again? So thatís why the construction ended with the Cascode preamp. Then the idea was to second convert, use a 30 MHz communications receiver, and from there on in use the communications receiver.

So first switch frequency, not knowing exactly how wide the line would be, the very first thing I tried was an electric motor with a generator coupled to it, with a Lucite disc that had been coated, half of it metallically, and spin it near the tank circuit of the L.O so that I would get a 30 Hz frequency shift, sin wave. And I managed to get a pulling using a standard National Radio, which was located locally in Medford. So if I had any problems with my IF strip, Iíd just hop in my car and go over to Medford and say, "These are the things I want to do." So I mounted that up and I used the generator for the reference to feed my synchronous detector. It was a very simple way to drive the motor and drive the disk and noted that the frequency shift was about 10 kHz. And no line because we were inside the line.

Sullivan

Switching at a rate of 30 Hz, 10 kHz away?

Ewen

Right. 10 kHz was all I could moving a disc up near the tank circuit without completely loading the circuit.

Sullivan

Did you sit down and think once again about motion from the galaxy or turbulence?

Ewen

No.

Sullivan

So you were just sort of move out until you could maybe get it?

Ewen

No, I was looking at it more- the physicist part of my "mountain" was saying to the "valley", "Let's get the frequency right and let's admit that the line width is pretty much unknown and itís going to be about as gobbledygook as the optical lines or some of the infrared stuff thatís come out." So, let's stay loose on that part of it and not make that a "buried-in-concrete" part of the design. The electrical engineer was saying: "Let's do the best upfront, as far as using an antenna that most people will understand, build it in waveguide, design a mixer based on a unit home-grown at Harvard, well at Rad Lab, Bob Pound, use a Cascode preamp grown over in Raytheon, and design and build this as carefully as possible and hook it up with a communications set that comes from Medford, National Radio, and then proceed to fiddle with things like bandwidth and switching rates at a level of convenience so that at least you donít"- I knew if I switched 10 MHz, it would probably work but I probably wonít get the job done before 1960. So it was, "Letís not do anything on the tail end that would embarrass us later, think whyíd it take so long."

Sullivan

Now, when you say you did not detect the line when switching 5 kHz or 10 kHz away, did you tune the L.O. over a broad range before you made that decision?

Ewen

Right. The L.O. was turned over a range of about Ī 150 kHz.

Part 2 | Part 3

Modified on Tuesday, 16-Dec-2014 15:52:54 EST by Ellen Bouton, Archivist (Questions or feedback)