RADAR Question?

**bigross86** · 14 Apr 10,, 23:12

I put this here, since RADAR was first used to detect aircraft, before it branched out.

RADAR started out in England in 1940 as a way to detect aircraft.

The ENIAC, commonly hailed as the first computer, was unveiled in 1946.

What did they use to control the RADAR and make all the necessary calculations (Doppler, Speed, Bearing) before they had computers?

**Stitch** · 14 Apr 10,, 23:40

IIRC, there were actually separate RADAR sets for ranging and direction; Doppler-shift RADAR didn't get invented until the 1960's. I believe the earliest RADARS (like the ones the British used on their south-eastern coast in WWII) were single-function RADARS: they could only range OR tell direction, not both. I don't think they needed a computer to run them (unless it was a very simple mechanical computer) since they were only single-function; I believe they used a simple oscilliscope on the first RADAR sets to "read" what the RADAR had found. This is more or less conjecture on my part, I'm sure someone here knows A LOT more about RADARS than me.

**avon1944** · 30 Apr 10,, 02:23

The first radar sets used a simple analog computers in order to get the oscilliscope (or "A" scope) to display the limited information in the proper perspective. The three towers of each "Chain Home" radar sites. The middle tower transmitted and the outside two received only. There is a math function (the 'cosecant' I think), between two separate sets of antennas, that has a proportion between the time difference between each of the two outside antennas to the middle antenna as to the angle of the return.
Using the speed of light figure of 186,000 miles/sec. was used to determine the distance but, was found to lack accuracy, so there became a real need for greater accuracy in the actual speed of light. The last I have heard was the speed of light is 186,282.4XXX mph (299,792,456.2±1.1 m/s).

**RustyBattleship** · 30 Apr 10,, 03:18

Not only that, but all the RADAR of that time could do was tell you what direction the planes are coming from. They could not tell you how many or even what altitude they were at.

Still, it was better than nothing.

As for the first computer not appearing until 1946 (after WW II) I think is incorrect. Years ago I watched the PBS series "The Machine that Changed the World" on the history of computers.

The first ones that you could consider "electronic" were used only to calculate probable accuracy and ranges for artillery as information was typed in as to projectile characterstics, angle of fire, muzzle velocity, impact area, etc. What was interesting about it was that this was done in WW II and the "technicians" who fired the guns (and they showed a movie clip of it) were all women --- in Army uniforms.

Analog computers had been around for quite a while. They were strictly mechanical-electrical using cams of varied sizes for calculating barrel elevation. A similar set of analog computers were still being used in M-48 Patton tanks well up into the 60's when I was in. But they were not electrical, strictly manual by turning a hand crank to set the type of round and estimated range for super elevation of the tube.

RADAR electronics have come a long ways since the 1940's. Amazingly, one of the biggest announcements about how powerful we could build them actually made headlines in the Milwaukee Journal --- "RADAR BOUNCED OFF OF MOON".

**USSWisconsin** · 30 Apr 10,, 04:04

Originally Posted by bigross86

I put this here, since RADAR was first used to detect aircraft, before it branched out.

RADAR started out in England in 1940 as a way to detect aircraft.

The ENIAC, commonly hailed as the first computer, was unveiled in 1946.

What did they use to control the RADAR and make all the necessary calculations (Doppler, Speed, Bearing) before they had computers?

ENIAC was an early electronic computer, but the first ones were actually adaptations of telephone switches built by a British Telco engineer, they were a WWII secret and didn't get much publicity. In the late 19th Century a man named Charles Babbage developed an mechanical analog computer, using hyperbolic cams and complex gears he called the "Difference Engine", it could actually do differential calculus problems once it was programmed by Ada Lovelace (Lord Byron's wife). I am unaware of its use in artillery calculations, but it could have been useful in calculating exterior ballistics. The defense department developed a programming lanfuage named ADA named in her honor.

**Monash** · 30 Apr 10,, 13:53

Originally Posted by RustyBattleship

Not only that, but all the RADAR of that time could do was tell you what direction the planes are coming from. They could not tell you how many or even what altitude they were at.

I was under the impression that the British initially worked out the position of the contact by comparing the bearings given by two different radar stations. These bearings being fed back from the radar stations to their air defence command who matched the bearings to work out range and location. Two readings taken a few minutes apart allowed them to work out a rough speed and heading.

In addition the strength of the reflected signal gave the operators a (very) rough estimate of the number of contacts i.e. depending on weather conditions one reconnaissance aircraft gave of a weaker reflection that 100 bombers flying in formation. (it took experienced operators to do this and the number of aircraft reported was always a "guesstimate".)

After this the only unknown variable is altitude. I'm guessing here and please I'd appreciate an expert telling me if I am wrong but by trial and error i.e. using your own aircraft you can set:

A) The altitude they are instructed to fly at (and their aprox. rate of climb);
B) Their air speed;
C) The time they take off;
D) The distance between your radar station and the aircraft's air base;

Once you know those variables all you need to do is measure the precise time your aircraft is first detected by radar. Allow for curvature of the Earth and you with the calculating machines available at the time (plus a large number of tests) you could work out a (even more) approximate height i.e. the contact is above 10,000 ft and below 20,000 feet or above 20,000 feet and below 40,000 etc.

Does anyone know if I am barking up the wrong tree?

Regards:

**Tin Man** · 30 Apr 10,, 17:03

CHAIN HOME has been considered "primitive" by some historians, but it was the pinnacle, at the time (1935") technology, and a very complex system. The budget for it was unlimited because it was deemed so important. Chain Home was VERY, VERY successful.

Performance...Chain Home could give RANGE, BEARING, and ALTITUDE, for bandit numbers, this relied on the operators and their experience, and this was cross referenced with the other stations, as was all data, to get correct enemy strength. This was done in the "Filter rooms".

Some unknown CHAIN HOME facts...
1. C.H. was actually used to track German V2 launches, yes, honest, it was used to calculate V2 trajectory, and even a launch point, which was passed on to the Mosquito squadrons to try to attack launch sites. This was TEN years before the US Ballistic Missile Warning system, or BMEWS.

2. C.H. had VERY long range and used a scanning method called "floodlighting" to "look" into continental Europe.

3. C.H. had, inbuilt, ECCM measures that were extremely effective.

Chain Home was not some ad-hoc system botched together, it worked brilliantly, was difficult to jam, gave accurate air raid information, and all the elements it used come together to make that happen, reporting, filtering, comms, and all this before the Cavity magnetron was invented. Impressive.

A single C.H. station did not have to rely on other stations to perform, it was all integrated at each site individually. The transmitters and receivers were separated by a few hundred yards to make it all work.
What made it really work was the coordination done at the control centres who sorted all the data out, comms by secure high grade landlines.

On computers, IBM officially produced the "FIRST" electronic computer well after the war, but the computer called the "TURING BOMB", invented by a post office engineer and Alan Turing and his team was the first computer, but ULTRA was a secret for 50 years so the Bletchley park mob had to keep quiet about IBMs "first".

A Charles Babbage type machine was proposed to the Admiralty before WWI to be used on battleships to calculate gun laying solutions, but the system was incredibly expensive and rejected.

**Tin Man** · 30 Apr 10,, 17:24

CHAIN HOME.

1. Altitude- To find enemy aircraft altitude....A C.H.station would have two receivers for height finding, one at 215 feet height, one at 95ft. Height being calculated by the signal strength ratio from the returned signals by a electro-mechanical computer called the "fruit machine" .There was also a third stack at 45 feet which acted as a "gap filler".

To answer Bigross, "computers" were actually used but not the electronic ones we have today of course. The elecro mechanical type with cams, gears and other gizmos, basically a babbage machine with electricity introduced to turn everything

**Silent Hunter** · 30 Apr 10,, 20:17

Originally Posted by Tin Man

On computers, IBM officially produced the "FIRST" electronic computer well after the war, but the computer called the "TURING BOMB", invented by a post office engineer and Alan Turing and his team was the first computer, but ULTRA was a secret for 50 years so the Bletchley park mob had to keep quiet about IBMs "first".

I think you're confusing the electo-mechanical bombe (in fact a Polish design) with Colossus, designed to crack the German Lorenz ciphers.

**Tin Man** · 01 May 10,, 00:23

Originally Posted by Silent Hunter

I think you're confusing the electo-mechanical bombe (in fact a Polish design) with Colossus, designed to crack the German Lorenz ciphers.

Ah yes, serves me right trying to write from memory.

The British bombe was a "development" of the Polish machine, which could only handle 3 rotor Enigma ciphers, and operated on different principles designed in by Alan Turing to handle the 4 rotor Enigma. (I just read this).

Colossus I and II "may" be more correctly described as the first computers, designed to break Lorenz teleprinter messages. Colossus ran first in 1943. Many people still refuse to call this a true computer either. The US ENIAC was started in 1943, but never worked until 1946, so did nothing for the allied war effort and was obsolete by then anyway. ENIAC was the parallel of Colossus.

Generally I would credit lots of people, Babbage, Turing and Newman for the computer along with Hungarian Atanasoff who worked for the US. But Turing was "The man".

It all depends on your definition of a "computer".

Anyway, I would credit Turing the most, with his 1936 paper and his proposal for his Universal Machine, an electronic computer, which was working at Manchester University in 1948 and used RAM storage.
For me, it is this development in Manchester form Turing, Newman ,Williams and Kilburn that shaped what we have now.

**treasure44** · 01 May 10,, 10:12

Originally Posted by USSWisconsin

ENIAC was an early electronic computer, but the first ones were actually adaptations of telephone switches built by a British Telco engineer, they were a WWII secret and didn't get much publicity. In the late 19th Century a man named Charles Babbage developed an mechanical analog computer, using hyperbolic cams and complex gears he called the "Difference Engine", it could actually do differential calculus problems once it was programmed by Ada Lovelace (Lord Byron's wife). I am unaware of its use in artillery calculations, but it could have been useful in calculating exterior ballistics. The defense department developed a programming lanfuage named ADA named in her honor.

I believe they used some sort of computer like this at Bletchley park to work on ULTRA

oops been covered!