Doppler Navigator Development

J.N. Barry

Notes on the Development of the Light-Weight Navigation Doppler Radar in DRTE

(This brief history of the Doppler Navigation Project was prepared at the request of Frank Davies when he was working on writing the history of DRTE - ed.)

Mr. Davies, in the interest of getting on with this little task, I have decided to transcribe some of my recollections on tape and have them typed. I am certain there will be several gaps which I will have to check with people but I hope to get at least the essence of the story down so that you could begin to have a look at it and be able to decide how you wish to treat the topic in your little history of DRTE. In presenting this material this way, I am taking your request fairly literally, that is to say I will stick mostly to dates and milestone events and perhaps the names of some people and I will leave it to you to put it into the final form.

My Story begins:
When I arrived in Ottawa after a cold and wintery trip from Halifax in February 1953, I was greeted by Mr. Bert Walker, Mr. Keith Brown, Mr. George Lake, Mr. Nick Nichols and Mr. Dick Steacie and introduced to a confidential project to develop doppler navigator radar. This project was already underway, Mr. Walker gave me to read some calculations he had already made on the strength of signal vs. height for various configurations of radar antenna patterns. I was assigned to work with Mr. Jack Bloom, with the support of Mr. Clare Frayne as a technician. My assignment was to develop a precision oscillator which would eventually be used to track the doppler, but to develop it in a way that the frequency developed in the oscillator would be linearly proportional to a shaft position. (The reason for this was that for encoding ground speed, which was derived by tracking the doppler, we had to go to a mechanical system; we therefore had to have a linear relationship between the frequency and the shaft angle which indicated ground speed.) Jack, of course, was bombing along on this project in his usual great enthusiastic manner and I worked for him for many months on this scheme. It eventually proved to be unworkable, not through any fault of Jack's, but because we were not able to build inductors to satisfy the linearity requirements.

The background of the whole project doppler was really not well known to me. I learned subsequently that the interest had arisen because of the requirement to fit out the F105 (Avro Arrow) with a light-weight doppler system. It was well known that the British had developed a pulsed system called Green Satin for their bombers. Being a system with magnetrons and in general heavy equipment, it was contained in two pressurized drums and weighed in at about 300 Ibs. You have already remarked the target for the light weight system was to have one that weighed the same as a man, say about 150 Ibs. A decision was taken earlier on, at least as a target, that the DRTE development would not require to be pressurized. It was for this reason that all our work was done on a low power CW system as opposed to pulsed and we were working exclusively with klystrons and other low power components.

Somewhere along this period. Dr. Walter Clarke also joined our group and contributed a great deal in the way of studies. He also conceived one configuration for thp radar which we spent a lot of time developing. Basically the configuration was satisfactory in principle and we were able to prove it out in the laboratory. In fact, we even received some true doppler but in a sort of reversed way: we aimed the radar out the window and flew an Expediter aircraft towards the window of the laboratory to get the doppler. George Lake was the lucky passenger. The basic failing of.-the system, however, was that it could not, in any way, shape or form, be kept in proper adjustment. It required a 'tweaking' up to the nth degree to avoid hopeless levels of noise in the receiver.

Keith Brown can give you more explicit information on other generic types of radar that were tried. He, not I, was doing flight trials when I first came; I had been put with Jack Bloom on oscillator and tracker projects. Also, I was diverted for about 1/2 year on the lone Wolf project around 1954.

Well, to make a long story short, the development went from one configuration to another, all of them really unsuccessful until Keith Glegg fame up with the invention of the frequency modulation mode for the microwave subsystem. The timing of this invention was especially critical since - you might recall precisely, I only got this second hand - there was strong pressure on the Air Force, as we were not having much success, to buy a pulsed system from General Precision Laboratories in Boston, allegedly to tide them over, so to speak. This battle was almost won by GPL in our Air Force Headquarters. The persistence of W/C Craig - you will have to check that name with Keith Brown - saved the day. I was given to understand that Craig was a strong ally with the project and kept the funds coming.

I'm not certain at what point Marconi was given the contract to work with us - it must have been after Walter Clarke's model was tested -but, basically, as it turned out in the end, Marconi was doing the antenna design, RF and IF amplifier construction, with DRTE accountable for all of the video section and signal processing, including the tracker and the wind-speed computer, the planning of the development, and the integration and flight trials.

According to some of the old records that I have the first successful operation of the doppler in the FM configuration was November 30, 1955, and I have enclosed a photograph of the page from our diary which gives the comments and shows the signature of Harold Raine - note that the entry has no "Eureka!" - we were all getting wary by then.

Interestingly enough, the equipment was installed in the aircraft at Montreal and worked straight away - it worked all the way to Ottawa and subsequent flights in the next few days showed the equipment worked extremely well - much to everyones elation, of course.

The next milestone which might be of interest is high altitude tests in the in the CF100. I have attached a picture of Dave Boulding and Ted Stafford putting the doppler radar into the rocket bay of the jet airplane, number 219, which was an aircraft turned over to us for our purposes. These were the trials that finally proved that the theoretical performance of this system could be approached by careful adjustment and attention to design detail. I would emphasize that in getting the proper signals at high altitude and high speed, we had to solve a lot of tough engineering problems having to do with interference, vibration, cross-talk and the like. I don't know how many flights were made but there were a lot of them. We had instrumented a tape recorder to record the doppler in the CF100 and in reflection it was surprising how much we were able to do in the way of instrumentation without modern-day sophisticated telemetry and the like. We took ordinary instrumentation and developed peripheral electronics to go with it that would ensure us useable and accurate data.

The next milestone that I would refer to is in 1957. Wing Commander Wright, who was of course a strong proponent of the R-6 computer, approached us in the laboratory and asked if it would be possible to configure both the doppler navigator and R-6 computer so as to have a fully integrated system. He brought over, as was his custom, two or three chassis under his arm - no mention of inventory in those days! - and left them with us.

We spent two or three weeks looking over the drawings and set a technician to work. After a couple of months we had the R-9 installed in the old C119 Boxcar and hooked up to the doppler. The first time it flew it worked great. Being myself, a complete novice in avionics, I was completely dazzled by this wonderful system we had in which we could measure true ground speed and track and feed it into the R-Theta computer to get indications of how far away you were from home and which direction home was. In my naive way, I figured that navigators and pilots must surely have come into the millennium.

This experiment was important because we had reliable ground speed and track for the first time for the R-9 computation. Hence it not only verified the accuracy of the doppler, it verified the ability of the R-9 to give an exact answer to the solution of these navigation problems. The highlight of this task was our flight to Greenwood, Nova Scotia in late 1957 to do over-water trials. We ran the doppler and the R-Theta all the way. The records show that the equipment functioned perfectly and when we arrived at Halifax the R-Theta had a residual error over the airport which was well within expected limits. Photo of an early log entry is included.

From 1957 on things moved very rapidly. I will take a moment here to recapitulate what we had at that time. We had a fully operational parabolic antenna system that Marconi had developed, complete with the Geneva drive which caused the slotted array which fed this antenna to roll over and alternatively send the beams forward and backward; this of course was another Marconi development. We also had a fully stabilized platform which we had built at the laboratory with a vertical reference gyro; the equipment was always level. The antenna system was, of course, mounted so that it could swing to the right or to the left to follow the drift angle of the airplane - this was in fact the way the drift was measured. The radar was caused to track the line of flight by swinging either to the right or left while the aircraft maintained its own heading, and the drift angle which was used to compute the wind was simply picked off by a synchro. We had the reasonably well- engineered RF front end with the frequency modulation system and we had all of the Marconi-derived IF equipment. We had the wind speed and ground speed computational triangle that had been built by Dick Steacie. Dick had by this time left the laboratory but he left an excellent piece of equipment behind for us which for several years gave very little trouble. We also had the doppler tracker which had been designed and built in the lab. We had also a host of very high quality power supplies for all of the various circuits. Perhaps a word is in order here that Gerry Williams, in Frank Simpson's component group, undertook to regularize the design of 400 cycle transformers for aircraft service and set out a set of guidelines for Clare Frayne which enabled Clare, who was himself a very intelligent character, to meet all our requirements for all manners of 400 cycle transformers; they were virtually in production on these things because Marconi used to demand so many of them for the power supply - of course we did too.

At the same time they used to demand all kinds of audio transformers. Clare Frayne and Doug Way-Nee spent weeks and weeks putting transformers together. It was a time when it was better to build your own than to try and procure them from the trade because the trade wasn't really interested or capable to make this high quality stuff on short order.

Another aside that I might mention while I think of it is that it was during this period, 4 to 5 years, that Frank Simpson's group was studying all forms of encapsulation for aircraft components and circuits - you may recall seeing circuits cast in Araldite; there was also all the so-called conformal coating techniques for circuit boards. This was a time in which printed circuit boards were developed, and there were special techniques evolved in coating them with varnish and lacquer to keep components dry and in place. All of this work was done with a view to potting or coating avionics circuits but, as is often the case, this was not done in the versions of the doppler that we made. However, all of this know-how was put directly to the Alouette I job when we undertook it and we reaped the harvest of almost 10 years of work by Doug Way-Nee and his colleagues on encapsulation and protection of electronic circuits. In fact, these techniques survived in all the subsequent models of Alouette I which were built in the companies.

Another point I would make here, that has also to do with Frank Simpson's program on components; the components that we used in the doppler were selected carefully through screening at CAMESA. Additionally, our own staff regularly sawed components in half and examined them for their quality of construction. What I am saying in essence is we had quite a thorough, perhaps one of the most thorough, component evaluation schemes In business. Also a fact which stood us in good stead when it came time to build Alouette I.

Well, I must go back to my story.

Around 1957 we had basically assembled all the elements of the system and from there on things moved very rapidly. I returned to University and, of course, lost track of the project in detail but for the next year a long arduous series of evaluation flights were made over all manner of terrain. Included were long lengths of rail-road track which the CPR kindly measured for us by chaining it so that we could evaluate the precision of the doppler and the tracker that went with it. This was no mean undertaking because we were looking for precision to a 10th of a percent and there were not many places on the earth surface where you could
(a) fly a straight line, and
(b) get a measurement many miles long, with this accuracy.

The CPR gave our staff all manner of drawings of their tracks so they might find the straight sections.

It was right in this period of course that the Avro Arrow was cancelled and the main and immediate mission that was forseen for the radar was lost. However, Keith Glegg and John Killick, who was then in DDP, went around this continent like two travelling salesmen, exhibiting this equipment to whoever they could and eventually over 2000 sets were sold to the USAF at some $50,000 apiece, and they sold of course, sets to the US Army. I'm getting out of my depth here because I really don't know what the market was, but I know that they had sales of over $100,000,000 on the first configuration.

The first configuration was to all intents and purposes a tube model. There was Dick Steacie's mechanical wind solution triangle of course which used transistor amplifiers but the radar, both RF and the video sections, and the tracker, used tubes except in isolated incidences. This was the configuration that Marconi went with. By 1959, of course, Norman Moodie's people under Colin Franklin had completely transistorized and flight-tested a radar and it was offered to the Marconi Co. but I believe they were unable to agree on proprietary rights - either that or rates - and Marconi never elected to take up the option of the transistorized doppler. So all of these original sales, in great quantity, were made using the original tube version.

That in a nut shell, is my recollection of this great saga. I guess it could be said that it started about 1952 and our laboratory's involvement with it ended around 1959 when the Alouette project came along.

I have not made mention of three important aspects of this program:
1. The wonderful co-operation of the RCAF. We had pilots and navigators who flew very difficult and tiresome missions. It was said of some of "our" pilots that "he'd fly a wheelbarrow if you'd put a stick in it I"
2. The almost casual but totally dedicated common approach to the project taken by the government lab and Canadian Marconi scientists and engineers. A common attack on the problem for example the RF section, was the spirit. There was seldom, if ever, a word over who had bungled what or arguments as to who was to do what.
3. The close association of a manufacturing capability to the project ensured that at completion there was someone able to build it for a profit. It would be difficult to overstate the importance of this lesson. Technology transfer is a hell of a difficult job.

John N. Barry
17 September 1973