Interview with James H. Trexler

Sullivan: 00:00

With James Trexler at NRL on 18th of March 1974. Now, can you give me some idea of the early development of radar as you see it, and then how and why you got involved in it?

Trexler: 00:14

Oh, you mean radar astronomy?

Sullivan: 00:16

Right. Radar astronomy, right.

Trexler: 00:17

Well, my first connection with this was, I believe, in about '36, 1936. I think, about that time, Allen of the FCC, chief engineer for the FCC, had some papers in the popular radio journals about the reflection of radio signals from meteors. And it was fairly easy to look into this because at that time they were experimenting with VHF FM stations. I believe the stations were in what is now approximately channel one of what is now television. It was just below the television band, and there was quite a bit of interest generated by Armstrong and others in FM communications. And the sudden bursts of signals that were received from very distant FM stations were first attributed to meteors, meteor trail reflections, I believe, by Allen. And this looked like an interesting project to get into as a college engineering physics kind of thing. And in connection with the engineering and the physics department at Southern Methodist University, I was given help from-- I believe it was called NYA [National Youth Administration]. Was it called NYA? It was a government help for students kind of thing.

Sullivan: 02:03

During the Depression, yeah.

Trexler: 02:05

I was given a couple of students to help in building antenna arrays, and we built several directional arrays to determine the direction of arrival of these signals, which we thought were reflected from meteors and eventually built under the direction of Dr. [Luce?], who was our professor, Dr. S.G. [Luce?], we built some instantaneous DFs using Adcock antennas.

Sullivan: 02:41

The direction finding, DFs?

Trexler: 02:43

Yes, direction finding. It's a system of direction finding which displays the instantaneous arrival angle, the signal, on a cathode ray tube. And this was relatively new technology at that time. And we used a new and very exciting cathode ray tube that was built by RCA. It was one inch in diameter, and could be built right into a movie camera, very handily. And we were able to show that, indeed, the signals did seem to arrive in the meteor trails. And it was an undergraduate engineering project at Southern Methodist University.

Sullivan: 03:23

Was this published at all?

Trexler: 03:24

There were no publications in regular journals. There was a very abbreviated publication in a school paper, school journal. But this work led directly to my being hired here at the Naval Research Laboratory in 1942, and I went into the direction finding business here at the Laboratory, which was, then, completely oriented towards detection of German submarines. And it wasn't until the end of World War II that we went back again, starting looking at the reflection of meteors as a way of communicating, burst communication, between remote points, distant points, using reflection from meteors. And--

Sullivan: 04:17

What would be the idea? You'd be continuously transmitting a signal, and, only once in a while, would it get through--

Trexler: 04:23

That's right.

Sullivan: 04:23

--when you haven't had a meteor?

Trexler: 04:25

There were various techniques devised. One was to have the receiving station listen and when he heard a signal from the transmitting station to return the signal and that would tell the transmitter to start sending traffic and send traffic until the traffic would fail at the other end. Various systems were devised. Some of them could unload at a rate of equivalent of 60 words per minute by sending at very high speeds during the first [cells?]. Of course, it depends on the number of meteors per hour. And sometimes in a day, the meteor count sometimes--

Sullivan: 05:00

[crosstalk]--

Trexler: 05:01

--in a day and year, the meteor count goes way down and your backlog of traffic builds way up. And then sometimes, when the meteor shower comes along, then you can unload the basket.

Sullivan: 05:10

Has this ever been used, this system?

Trexler: 05:11

Oh, yes. There were several military systems devised both by this country and other countries to use this technique and has actually been used on mobile platforms such as ships.

Sullivan: 05:22

What's the advantage over just using the ionosphere?

Trexler: 05:25

Well, it uses higher frequencies which--

Sullivan: 05:30

[crosstalk]--

Trexler: 05:31

--or you don't have the ionosphere, you can pass traffic pretty fast. It was just another method of communication and these kinds of things led to tropospheric and ionospheric scatter communication, which are getting us farther and farther away from radar astronomy. The early radar astronomy business as I remember was all associated, after the meteor business, all associated with trying to get echoes from the Moon.

Sullivan: 06:03

Let me just ask. Were there any publications from this meteor research's scientific aspects of it as opposed to communications[crosstalk]--

Trexler: 06:10

Well, there's been a very large amount of it published in the standard journals in the early '50s and so, and late '40s. I think that it would be in that time frame, maybe even in the '60s. The early aspects of it, because it was sponsored by the military, was probably classified, and gradually, it became a rather well-known technique but not a very happy one because it was intermittent [crosstalk]--

Sullivan: 06:36

Okay. I’ll just have to check on that. I'm not very familiar with that. Anyway, you were saying this got you--

Trexler: 06:42

Well, this business of getting off and trying to get echoes from the Moon was a challenge from the very earliest radar experiments to get echoes from the Moon. Mr. Young here at the laboratory who was the -- has been named as the co-investigator with Dr. Page and others of the early days of radar, was always on the lookout for long, distant echoes. He, very early, back in the '20s, I believe, identified round-the-world signals that he called echoes, with echo being the wrong word here. And they've got several-- got signals which have made several complete circles. But they were always looking for a Moon echo in this long delay, and without success. Even though they sometimes thought they had enough radiating power and enough sensitivity, they never quite made it. And as we know, other investigators and other countries worked on this. And then we had the US Army coming out with the first public announcement of it. I believe that was 46. This was announced very dramatically, the IRE, now IEEE, convention in New York, and almost immediately after that, other workers in the field started surfacing their results.

Sullivan: 08:15

But no one did do it during the War, though?

Trexler: 08:18

I don't know. There have been reports, many reports. Many radar operators have told me that they had strong suspicion of receiving Moon echoes on large military radars during the War, but it was suppressed. Information was suppressed because there wasn't very much information generally published about radars. And if you had a radar good enough to see the Moon, you certainly didn't want to talk very much about it. But I don't have any real firm evidence of this. I've also heard that one of the large radars installed, German radars, the German radar--

Sullivan: 08:59

Wurzberg dishes?.

Trexler: 09:00

--Wurzberg radar, installed at the Chesapeake Bay Annex of the Naval Research Laboratory, contacted the Moon very early. But I don't have any first hand information of this and don't know of any publications. But you might check in the radar -- maybe you ought to start with, oh, who is the associate superintendent of the radar division. Well, get that level of people there and see if they have any recollection of these experience.

Sullivan: 09:35

Okay. What about your connection with?

Trexler: 09:40

Well, our connection was quite backwards. We were interested here in the counter majors branch of NRL in determining if reflection of signals from the Moon would be useful as a method of intercepting signals. And to study this in detail, we wanted to produce our own signals and change their parameters and measure them. So that was the driving force. And then in the early '50s, we obtained some money to build a quite flexible radar for doing this. One we could change the frequency of and one that we could change the signal characteristics and one which would have enough effective radiative power and enough sensitivity to get continuous results and not just sporadic results.

Sullivan: 10:35

Right.

Trexler: 10:36

And so that's what led to the experimental work at Stump Neck.

Sullivan: 10:39

You're talking about this hole in the ground antenna which is described in the 58 Proceedings of the IRE?

Trexler: 10:47

That's right. And that installation has operated, if my memory is correct, from frequencies as low as maybe, 30 MHz up to as high as 400 MHz.

Sullivan: 11:01

Well, it says 198 to 3,000. Yeah.

Trexler: 11:06

Well, those were the successful operations at the time of publication. 3,000 was not done on that dish, they were done [inaudible].

Sullivan: 11:16

Oh, I see.

Trexler: 11:16

On the 50 foot dish on Building 43. But we have carried out with that dish in Southern Maryland, we carried out experiments down into the HF part of the spectrum, and since then it's been carried on by the large antennas of CBD down even lower, probably at least as low as 16 MHz, 12, 16 Mhz, and went on up then into the several hundreds of MHz rather almost without gap, almost continuously through the spectrum. And we think that we- or thought at least at one time, that maybe the path loss to a fraction of the decibels, had it tied down pretty well. One of the biggest confusing factors in that early work was the fact that we had something we call modulation loss, which was due to the fact that a  short pulse signal hitting the Moon would not illuminate all of the possible reflecting surface at the same time. And so as the signal washed across the Moon, you picked up later signals. But if the signal were longer, were not such a short pulse, then it would be--

Sullivan: 12:38

Illuminating the whole thing simultaneously.

Trexler: 12:41

Then there would be a gradual accumulation of that goal until you got to a continuous wave kind of situation which was many decibels stronger than you would have gotten with a very short signal. This led to the problem that for very short signals like ones of one microsecond length that it took a very high powered radar to contact them. But this has been accomplished now and worked by places like Stanford and Arecibo.

Sullivan: 13:08

Right.

Trexler: 13:09

[inaudible] have been able to muster enough radar performance so that they can look 70, 80 DB down into the noise and down below the peak signal, peak echo and even see the limb of the Moon, even see the edge, as well as the highlight at the center. I think the greater the-- not the greatest thing, but the most interesting thing that we discovered immediately here at the Laboratory when we made solid contact with Moon was that there was a highlight, an RF highlight at the center.

Sullivan: 13:45

That's what the point of this paper is mainly, this specular reflection here.

Trexler: 13:48

That's right, there's a [revolving?] specular point in the middle of the Moon. And this would happen for almost any planetary body like this and does enhance the echo, enhances the utility of the object as a relay for communications or as a probe for studying interstellar space. You have a smaller point there to work with, and it's been quite helpful in that respect.

Sullivan: 14:18

As you were doing this work, were there other groups doing similar work that you knew about anyway?

Trexler: 14:23

Well, of course, running simultaneously in parallel with us was the work going on at Jodrell Bank. And we had kind of an unofficial agreement between them that if one of us published the other one would at the same time and so this went on for quite a few years until finally at the URSI meeting in Boulder, Colorado. And in a year, I don't know which, but it was just prior to publication of this paper, Jodrell Bank people decide to publish their results of their Moon probe radar work. And we presented a paper, that is Naval Research Laboratory, presented paper on the Stump Neck, Maryland, work at the same session of the URSI meetings. And this was followed by-- well, I guess it was preceded by-- a paper by Collins Radio and the National Bureau of Standards did a joint piece of work where one of the forward scatter radio propagation devices being developed by Collins Radio was used to transmit from central United States back here in Washington to the National Bureau of Standards station in Washington at a fortuitous moment when the Moon happened to pass through the beam of this very large [inaudible].

Sullivan: 16:07

Is that published somewhere now? IRE Proceedings or--?

Trexler: 16:10

That was available in a popular literature, popular magazines. I don't recall it being in one of the scientific journals, although it may well be. I believe the work was done-- my memory, it was done at 400 Megahertz. Simultaneously, there were attempts made by the Australians to transmit signals over the Moon, communication-type signals. Although this was tried quite a few times, I don't believe that it was successful until later in the 50s.

Sullivan: 16:48

I assume that you were indeed sending all sorts of signals. It wasn't just a matter of detecting the Moon, but you were able to communicate with yourself quite well and so forth.

Trexler: 16:56

That's right. But as far as communication goes, we showed that the Moon circuit was better than had been anticipated by the early probe work by the Army at Red Bank. And I guess it is Red Bank station. And their system was so marginal and I'm not decrying the Army work. It was first and it was very good. But the signal level was so low that they couldn't really tell very much about what it was made up of and how it was made up. And we found that, in fact, we were several orders of magnitude higher quality or wider bandwidth transmission was possible. And that by putting a little bit of FM modulation on the signal to broaden its spectrum beyond the spectrum required for the communication rate, it is to make the signal artificially broadband. And I don't want to infer anything like what we call today's spread spectrum, but in reality a little bit of spread spectrum, we were able to reduce selective fading. And so that you wouldn't get into these deep null problems where the signal would disappear for a while and then come back.

Trexler: 18:14

Also, it was soon discovered, not by the Laboratory, but by other workers, it's referred to in the paper. It was discovered that there was a very pronounced polarization rotation effect. And as soon as that was realized, Faraday rotation was realized as the cause of this. You understand that Faraday rotation was a very well-known phenomenon. We just didn't tumble to the fact that it was so important in this problem. As soon as that was realized, then almost everybody using a certain circular polarization and got clear of that particular type of thing. We didn't pay much attention to it at first because we're working at such low frequencies that it was a fast form of fading. But as it went up in frequency, why up into the UHF? Why it became a slow and very—at 400 MHz, for example, became a slow and very embarrassing type of fading. You lose the signal for long periods of time.

Sullivan: 19:16

How long did this work go on with the Moon? Did it go on much after this article was published?

Trexler: 19:21

Well, there's been almost continuous work of some sort or other. The Moon circuit was first developed for point-to-point military communications. And the first points were tied together were Hawaii and Washington in the Navy communication circuit. And that was extended to other kinds of military communication. And we think of it as the first satellite communication, and predated the artificial satellite communication by quite a bit. Although it was never used at this rate, the, it was experimentally demonstrated that you could work 16 channel 100 word per minute per channel-- 100 words per minute on 16 channels simultaneously on one carrier.

Sullivan: 20:14

Is the advantage, once again that mainly higher frequencies can be used than in the ionosphere? More reliability about the--

Trexler: 20:21

That's right.

Sullivan: 20:22

--[reflector?].

Trexler: 20:22

And it paid off initially as a method of getting through when you had an ionospheric blackout. And it did handle a lot of emergency traffic into Hawaii from the United States for a few of those ionospheric blackout conditions but it was almost immediately overtaken by the submarine cable that went into Hawaii that would take [crosstalk]--

Sullivan: 20:48

But what about the problem of the Moon being there? I mean, it's only there--

Trexler: 20:51

Well, the Moon, of course, has to be available at both terminals and if the two terminals are very far apart then the amount of time goes down. Between Washington and Hawaii it averages about six hours per day and you have no control over what six hours those are [crosstalk]--

Sullivan: 21:07

So that's one of the main drawbacks, I suppose.

Trexler: 21:10

So it was used as deferred or backup communication. Early days in the Navy, use of it, it was used to handle a lot of routine administrative traffic and it could unload a vast amount of it. It was never used to capacity because the capacity was greater than it was even thought necessary at those times. Now, today, by today's standard of very broadband high-speed communication, it wouldn't have held up. Well, it served in that kind of capacity for quite a while, and it's interesting to note that about the time that it started to die down as a military communication medium system it started to pick up as an amateur radio communication and it's quite actively engaged in now by radio amateurs as a way of communication. Quite a few of them all over the world, South Africa, Australia, Europe, United States communicate on a regular basis via the Moon and with all of these completely homemade antennas and homemade charts on where to look and how to do it. And then one of the most interesting features that's appeared in the last few months has been that with this is very continuous and intensive observation of the circuit that on a few occasions reflections from something other than the Moon had been seen, probably shocked wave fronts from the [crosstalk]--

Sullivan: 22:40

Maybe [inaudible] or something.

Trexler: 22:42

From the [crosstalk]--

Sullivan: 22:43

What sort of delays? A few second delays?

Trexler: 22:46

Beyond the Moon [crosstalk]--

Sullivan: 22:47

Oh, beyond the Moon, I see.

Trexler: 22:48

And these have been associated, I understand, with outbursts on the Sun and things like this where there's a [crosstalk]--

Sullivan: 22:56

Very interesting.

Trexler: 22:57

--wavefront coming in to give a [reflection?].

Sullivan: 22:59

[crosstalk], yeah.

Trexler: 23:00

I'm not sure that this is well understood yet but at least some echoes of very long delay of this type had been seen.

Sullivan: 23:08

Reminiscent of the meteor trails again.

Trexler: 23:10

That's right. Only in this case, farther out. So there is interesting activity in that way. I would say that right now, though, that the use of the Moon as a serious communication medium has almost gone to zero.

Sullivan: 23:30

Did you do any more scientific investigation of the properties of the Moon per se?

Trexler: 23:34

No, that was under simultaneous investigation by Ben Yaplee--

Sullivan: 23:40

Yes, I talked to him. Right.

Trexler: 23:41

--and Nancy Roman.

Sullivan: 23:44

So you left that mainly to them.

Trexler: 23:45

And they carried that to considerable extent. And then later with the better equipment at Arecibo, they were able to actually get into mapping. And this, of course, has been carried out even to the more distant planets [crosstalk] quite high resolution and remarkable results. We in this group have never participated in that aspect of it although we have over the years tried to understand more about the statistical parameters of the echo from the Moon and for what good it is in terms of the dispersive circuit but more from an engineering propagation kind of then from an astronomy point of view.

Sullivan: 24:35

Would you be willing to make a few comments on the reasons that Sugar Grove never worked out? I mean, without getting into the mechanical reasons. Where did it go wrong and so forth? You were involved in that also [crosstalk].

Trexler: 24:49

Well, that's a very difficult one for me to talk about for two reasons. One, I was awfully close to it. The other reason is that there's still a lot of aspects of it they're not declassified. The problem there was that we were trying to build an antenna which was beyond the state of the art at the time and we took the risk of trying to start the job before the design was finished. This was considered at the time to be a reasonable risk.

Sullivan: 25:28

It was a calculated risk.

Trexler: 25:30

It was a calculated risk. It was a known risk. There had been a lot of money spent on the design. Probably more money spent on the design than almost anything up to that time. It's interesting to note that the company was the chief design company for the big antenna at Sugar Grove was simultaneously working on the Narrows Bridge, New York. And the staff on the Sugar Grove 600-foot antenna with more than 10 times the size of the staff on Narrow Bridge which was the biggest suspension bridge.

End tape 34B

Begin tape 34A

Sullivan: 00:00

This is continuing with James Trexler on 18th March, '74 from the other side.

Trexler: 00:07

I was talking about the calculated risk in designing and starting construction on the 600 foot parabola at Sugar Grove. One of the things that was one of the system that was so difficult it made it become so expensive and so difficult to do, was the fact that as time went on it was allowed to grow in complexity. It was felt first that if you're going to spend so much money and so much effort on a large antenna that you should at least make it operate to 3,000 megacycles, as we called it those days, to 10 centimeter wavelength. And this was a very great burden on the mechanical design. And the second feature that made it difficult was that National Academy of Science decided that if you're going to spend this much money on a large radio telescope, it also should be a large radar telescope and it should have the largest and best transmitters available to work at the highest frequencies possible. So those two--

Sullivan: 01:23

For radar astronomy?

Trexler: 01:25

For radar astronomy.

Sullivan: 01:26

I didn't realize that was also a goal.

Trexler: 01:28

So right away a staff was assembled and work was started on a 1 Megawatt, CW, continuous wave. 1 Megawatt transmitter to work at very high frequencies on this. And this brought up all kinds of problems about danger or to aircraft flying overhead and all these kinds of complications. The going up in frequency brought up the problem that no structure, no matter how carefully designed, at least as conceived at that time, could possibly have enough rigidity to work at a wavelength of 10 cm. So that to overcome this very difficult problem, it was decided to make the antenna continuously alive and self adjusting. This became an extremely complicated problem.

Sullivan: 02:19

This is an entirely new concept?

Trexler: 02:21

This was a new concept. There were alternate concepts underway. MIT was working on a way of stressing, prestressing and controlled stressing of the structure by building in sensors and stressing members in the structure to hold the shape. There were servo controlled antennas under design in Australia at the time. But the concept to be used to Sugar Grove was quite different, and that was to, if I can say it backwards, was to place a perfect parabola in the sky and connect it to a flexible steel support structure by continuously operating hydraulic jacks driven by sensors that were optical sensors. And these were all connected to an Invar steel tower which was the baseline at the center of the structure. This Invar steel tower was to take the total Invar output of the United States for three years. I'm saying this to give you-- I'm giving you some “gee whiz” numbers so that you understand that it wasn't a small project in anybody's imagination. A lot of this went forward. A special factory was built at the site in West Virginia, the largest factory in West Virginia at the time, multi-story, very elaborate to build the surface without problem.

Sullivan: 03:52

These were panels?

Trexler: 03:54

There were to be 100 panels, approximately 100 panels. And each one was to be built on site, being much too to be transported in, and they would be built as precisely as possible and stored outdoors in a three-year cycle and brought back in at the end of three years for trimming up after being cured in the natural environment. And they were extremely well made and they were rolling out on the production line at a reasonable rate. There were 13 of them spread out in the curing yards at the time of the cancellation of the project in 1962. And if you think that each one of these panels was large compared with most radio telescopes and cost about a quarter of a million dollars a panel and they were just the surface panels of this dish. The structure was being built by two mobile gantries which were much larger than the gantries used at Cape Canaveral or Cape Kennedy for the launching of the big rockets. And there were 400-foot gantries and mobile gantries. The structure itself rose to almost 200 feet above the ground before cancellation. The criteria for cancellation was very well studied by McNamara's office in the Department of Defense and it was determined that technology had outrun the proposal and that the country couldn't afford to support the new technology and the old radio astronomy or radio technology. And therefore the older system at Sugar Grove had been overtaken by events. This analysis was--

Sullivan: 05:59

That was mainly on the military side?

Trexler: 06:00

On the military side. There was no support, there was no appreciable support, no real support from the scientific community for a project of this magnitude. When the project went beyond the cost of a quarter of a billion dollars, then it became popular to, in the press and in the halls of Congress, to talk about the latest cost of Sugar Grove, and if you didn't have a bigger number than the other man, you weren't up to date. So the cost immediately started escalating by $100 million steps, day by day and soon killed itself because it was in the same category as a nuclear carrier or some other very, very large national project, and was under constant scrutiny. So the project was canceled. The steel and fabrication work that had been accomplished was dismantled and sold mainly for scrap and the residuals were mainly in the area of technology and a few facilities left at the site. For example, the large operations building is used today by the Naval Radio Station.

Sullivan: 07:15

A 150-foot dish there.

Trexler: 07:17

There are some smaller dishes left at the site which have been in operation since the 1960s. But the 600-foot dish probably ruined, for the astronomy field, the possibility of building a large dish in the United States, which is very unfortunate.

Sullivan: 07:43

It put a bad taste in the mouth of Congress.

Trexler: 07:44

And this is indeed unfortunate. But the technology developed on that dish did help in many other projects and may have helped eventually in building some of the larger antennas such as the one in Bonn in Germany.

Sullivan: 08:03

Yeah, in Bonn. Well, outside of Bonn, yeah.

Trexler: 08:05

But this was mainly due to the fact that large numbers of design people were brought together and did work on the project.

Sullivan: 08:16

Did the radio astronomers back it in the beginning anyway?

Trexler: 08:19

Radio astronomers, well, I think on the one hand, they were happy to see a large facility being built. On the other hand, they were unhappy that they weren't directing it. I don't think the radio astronomers could muster enough support at that time to build an instrument of this magnitude--

Sullivan: 08:44

Right, right I'm sure they couldn't.

Trexler: 08:45

--and probably would not have. The concept was growing at that time that large arrays were more cost effective and for some purposes this is certainly true. For the military purpose it was not true. We were unfortunately stuck with a problem of maximum gain and maximum gain from the smallest possible area.

Sullivan: 09:11

You need the filled aperture, yeah.

Trexler: 09:13

So we need the filled aperture which required this kind of a solution. So it was unfortunate. It's interesting to note though that the predecessors of the Sugar Grove system which is described in the IRE article really was the forerunner of the Arecibo dish. And there was a period in time when a large antenna based in Puerto Rico, a 1,000 foot dish in Puerto Rico, was considered to be a possibility instead of the Sugar Grove antenna. The reason for making the change was that the large fixed dish in Puerto Rico didn't have enough coverage time. It couldn't follow objects long enough and it required building more than one to do the job. Originally it was planned to build one in Hawaii and one in Puerto Rico to get more coverage--

Sullivan: 10:22

Both holes in the ground, yeah.

Trexler: 10:24

Both holes in the ground, both 1,000 feet, and to get the large scanning angles would require a more complicated structure than the present Arecibo structure which is limited to 20 degrees of scan. And the cost was not all that much better than a completely spherical parabola. And the difficulty in feeding the antenna at different frequencies simultaneously was so great that the decision was made, right or wrong by today's standards, not to go in the direction of a large fixed parabola. But the designers, the people who worked on the Arecibo antenna spent time here at the laboratory with us at Stump Neck, on the parabola although the NRL parabola at Stump Neck, the NRL antenna at Stump Neck is a parabola instead of a sphere. But we were aware of the [inaudible], and, in fact, the one that we proposed for Puerto Rico was a hybrid device which we call a Marston antenna which was to have a contact lens of plastic on the surface of the reflector which permitted greater scan angles. And this was one of the things that slowed it up was that it took such a large volume of plastic material which had a carefully controlled dielectric constant.

Sullivan: 11:57

So what is the gain of this now? It refracts deflected waves slightly, or they [inaudible].

Trexler: 12:02

The system is, I believe-- and I'm just talking off the cuff now-- it's many years since I've remembered it. I believe it's known as-- is it the magnum lens? It's a classic design in which there's a reflector with a lens in contact with it in a variable.

Sullivan: 12:23

In visual optics also.

Trexler: 12:25

Yes, it's used in light optics as well as radio optics. And we attribute it to Dr. Marston, who was in charge of the antenna techniques group here at the Laboratory at that time.

Sullivan: 12:38

This never was carried out on a large antenna?

Trexler: 12:41

No, it never was done on a large antenna. It is of a class of antennas like the Luneberg lens type, where plastic is used-- although the one that I'm speaking of, didn't have the variable density dielectric. Well, I've kind of--

Sullivan: 12:59

Yeah, well that gives me a bit--

Trexler: 13:00

--rambled on here awhile.

Sullivan: 13:02

Oh, it's been very useful information. Any other points that you can think of to make about anything?

Trexler: 13:07

Well, it's been about 10 years since I've hardly even thought of this kind of business, time.

Sullivan: 13:14

You said you talked with Jansky at any time?

Trexler: 13:17

Yes, Jansky came to the Laboratory in the early days of radio astronomy.

Sullivan: 13:25

You mean the late '40s?

Trexler: 13:26

And met here with various people, including people like Menzel, and talked about the possibilities of radio astronomy, what kind of experiments we should do, and so forth. And I believe he came to one meeting where Dr. Page at this laboratory - then the Director of Research - was making the initial plans for the 600-foot antenna at Sugar Grove. Jansky came--

Sullivan: 14:03

Well, he died in 1950.

Trexler: 14:05

Oh, no.

Sullivan: 14:07

You're getting mixed up with his brother, perhaps? Cyril? I mean, Moreau?

Trexler: 14:10

No, no. We were into this business, believe it or not, we were into this business as early as '48.

Sullivan: 14:18

The large reflector?

Trexler: 14:19

Yeah, well large antennas related to moon work and space work. We had large antenna arrays and working on these kind of signals as early as '48.

Sullivan: 14:29

I see.

Trexler: 14:31

So it came very close after the war.

Sullivan: 14:33

Do you have any feelings as to Jansky's involvement in radio astronomy at that time? He obviously wasn't able to do it at Bell Lab, so.

Trexler: 14:41

He was considered kind of a senior scientist, you know. He didn't presume to be an astronomer, but his position in the organization, Bell Labs, was enough to give him prestige and I think he was well thought of by everybody. And of course, there were very few radio astronomers--

Sullivan: 15:10

Oh, sure.

Trexler: 15:11

--in the early days, just a handful of people.

Sullivan: 15:15

Do you know anything about-- I've heard that he had proposals for a large reflector at Bell Labs which they weren't willing to build for one reason or another.

Trexler: 15:26

It seems like I do remember something about that. They did put up a reflector at Bell Labs eventually. I don't remember whether it was before or after he died. They had one that was-- I guess it was used for some of their microwave link studies, or when it amounted later, came out as microwave links. But they did seem not to push that side of it very fast. Of course, they came through with their sugar scoop antenna up and running, which was much later.

Sullivan: 15:58

Yeah, that's been amazing what Bell Labs has contributed to radio astronomy, considering the percentage of time they spend. Well, thank you very much. It's been most useful.

Trexler: 16:06

Well, I'm happy to talk to you.

Sullivan: 16:08

On 18 March, '75 at NRL. This is the end of the tape.

End Tape 34A