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RADARChuck Hobson BA BSc (hons)

G0MDK 2INTRODUCTION

This presentation starts with the early beginnings of Radar in the United States and Great Britain. It moves on from there to describe various military and civilian radars, how they work and what they look like. In keeping with this, I shall first kick off with my own early beginnings and how I fit into the picture.

I was born and raised in Pittsburgh Pennsylvania, which is located at the heart of the US steel and coal mining industries. My early years were spent there during the Great Depression. I graduated from High School at the age of 17 in 1944. Like most young men in similar circumstances at that time, I contemplated my future, which included the military draft and a life time working in Steel Mills. With such a future to look forward to, I became very depressed indeed.

Then one morning while walking in down town Pittsburgh I spotted a US Navy recruitment poster in a Post Office window. My spirits soared. “US Navy wants young men in Radar!” I rushed into the Post Office where I suddenly found myself confronted by a very intimidating US Navy Chief Petty Officer.”So you want to join the Navy”, he asked? I mentioned the Radar poster and he said I would have to pass a written test on mathematics and physics to get into the Navy’s Radar school. I was really elated as those were my favourite high school subjects.

I said I would like to take the test please. The Chief said It was called “The Captain Eddy Test”, which consisted of 80 questions, and that very few ever passed it. He then handed me the test paper and told me I had two hours to complete it.

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(continued)

I completed the test in an hour and 10 minutes and handed it back to the Chief. He asked me, “What’s the matter, can’t you answer the questions?” I told him I finished the test. He marked it and graded it a pass. The chief then handed me an official looking US Navy form and told me to give it to the doctor in an adjoining room.

The physical exam took about 5 hours, It was truly an ordeal. Having passed that I found myself on my way to Boot Camp the following week with a Seaman First Class rating (S1/c). After surviving four weeks of accelerated boot training, I went on to attend a suite of US Navy technical schools. The first was called “Pre-Radio School.” It was a gruelling four weeks of mathematics. I managed that (30% survival rate). From there I went on to the next level, “Primary Radio School” for 3 months. It included electronic theory, some higher math, and building elementary receivers. After finishing and passing that, I went on to the final level, “Secondary Radio School.” That lasted six months. This school included a lot of electronic theory, which was taught in the mornings. The afternoons were taken up with extensive hands on experience: Radar and Sonar sets, Communication gear, and Navigation equipment.

I graduated in the top 10% of the class and was awarded a second class petty officer rating. (RT2/c) It was not because I had a super brain, but because I was adicted to electronics and completely immersed in my studies. (The Nerd mode)

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(continued)

During the next 6 years I served aboard various Naval ships and on shore stations repairing any and all kinds of Naval Electronic Equipment. If it contained vacuum tubes (valves) magnetrons and klystrons, I had a go at it: Fire Control, Air and Surface Search Radars, HF/VHF/UHF Transmitters and Receivers, Loran etc. That experience along with the Navy’s education/training in Radar set me up for life in the field of Electronics. In the process I became quite familiar with many kinds of Radars, which is what this Radar presentation is all about.

The next slide shows a picture of the USN Recruitment Poster I saw in Pittsburgh, a photo of me taken in Boot Camp and and another of an early US Navy Destroyer Escort. From there the presentation goes strictly into Radar.

G0MDK 5MY BEGINNINGS

US Navy Recruiting Poster 1944

S1/c Chuck Hobson Jan. 1945

US Naval Destroyer Escort DE-316

G0MDK 6WHAT IS RADAR

• RADAR: RAdio Detection And Ranging (American)

• RDF: Radio Direction Finding (British)

• Doover: Australian equivalent to thingamajig

• Radar transmits short high powered burst of RF energy

• RF energy travels towards aircraft at speed of light

• RF illuminated aircraft re-radiates signal back to Radar

• Radar measures RF energy round trip time (12.3µs per nm)

G0MDK 7RADAR USERS

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NOTES: PAR = Precision Approach Radar ASDE = Automated Surface Det Equipment

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HOW RADAR CAME ABOUT IN THE U.S.

• 1934 – 1935 experimented with Pulsed Radar

• 1936 Demonstrated Pulse Radar 25 mile range (Air Search Radar)

• 1937 Installed 200MHz Radar on destroyer

• 1938 – 1945 Installed same radar on DDE’s DD’s CA’s BB’s Carriers and various other ships (SC series Air Search Radar)

• THE EARLY BEGINNINGS

• U. S. Naval Research Lab:

Typical Destroyer mast

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HOW RADAR CAME ABOUT IN BRITAIN

1933 Ionosphere sounding Experiments with HF

1. 1934 Examined HF fading caused by aircraft.

2. 1935 Deventry Experiments Demonstrated Feasibility

3. 1935 developed & demonstrated Pulsed Radar at Orfordness leading to construction of CH Radar

4. 1936 – 1939 Built the CH Radar system

THE EARLY BEGINNINGS

Chain Home Radar Transmitter Antennas

G0MDK 10THE TIZARD COMMITTEE

Scientific Survey of Air Defence Committee

Tizard Chairman Rector of Imperial College

Rowe Secretary Air Ministry

Wimperis Member Air Ministry

Watts Member Radio RS Supt.

This committee’s job was to. investigate new technologies for defense against air attacks.

Their 1st task given to Watson Watts was: calculate the amount of RF energy needed to disable the pilot and aircraft in flight?

His results shown it to be impractical. Subsequently Arnold Wilkins was asked via Rowe and Watts how he may help the Air Ministry with their task. Hence, efforts to develop Radar began. (This was in early 1935)

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ARNOLD WILKINS

ARNOLD WILKINS (1907 – 1985)

Expert on antennas & the behaviour of radio waves

Conducted Deventy experiment

Participated in pulsed radar tests at Orfordness

RRS known as Home of the Invention of Radar

Credit for invention given to Sir Watson Watts**

** 1933 Wilkins familiar with pulsed RF techniques Ionosphere sounding

Noted flutter of VHF (60MHz) signals from nearby Aircraft

Subsequently mentioned this to Watts

Joint Watts Wilkins memo presented to Tizard Committee

Led to Deventry Experiment, Radar tests at Oxfordness & CH Radar

Scientific Officer at the Radio Research Station

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THE DEVENTRY EXPERIMENT

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THE DEVENTRY EXPERIMENT

Heyford Bomber

Deventry Experiment Site

RAF Long Range Bomber

Prototype Flown in 1930

Speed 229km/hr (142 mph) Range 1480km (920 Miles) Ceiling 6400m (21000 ft.)

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ORFORDNESS

1. Radar proposal by Watts and Wilkins accepted and go ahead given

2. Highly secret work started Apr. 1935 at Orfordness an isolated place

3. A very austere operation

4. Test equipment 2 HF wave meters, 2 Avometers, & misc. VM & AM’s

5. Tech book Radio Amateur Handbook: Wilkins & other 2 were “Hams”

6. Erected two 75’ wooden towers for Xmtr and 4 others for Receivers

7. Transmitter problems: Flash over and pulse width Corona on ant.

8. Committee appeared on site expecting results (June 1935)

9. 50 metre freq. Used. Atmospheric noise problems.

10. Echo from Valencia A/C observed at 27km

11. Committee gave glowing report to Air Ministry

12. Shifted to 22MHz (14m) atmospheric problem went away.

13. Pulse width down from 50µs to 10µs

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CHAIN HOME (CH) RADAR

• Following Orfordness development work, a system of 20 CH radars were strung up along the south and east coasts of England just before World War Two.

• These radars gave the RAF a distinct advantage over the German Luftwaffe.

• These radars were able to detect incoming enemy bombers and provide the RAF with their range, direction and altitude (position)

• With this information the RAF could choose when and where, or simply not to engage the enemy bombers (A distinct tactical advantage)

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Map of Chain Home Radars

G0MDK 17CHAIN HOME (CH) RADAR

1. Pulse type radar operating at 20 to 30MHz Transmitter peak power: 350kW/750kW

2. Large HF antennas strung up between two 100 metre high steel towers for transmitting

Transmitted very broad beam to illuminate all aircraft in search area

Receiving antennas (not shown) provided azimuth and elevation data

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CHAIN HOME (CH) RADAR

1. Second set of cross type antennas on 60m high towers for receiving.

Cross Dipoles mounted on wooden towers

Antennas were used to DF on reflections from aircraft

DF was achieved by phasing cross dipoles with goniometers

Beam was shifted left, right, up and down with goniometers calibrated in az. and el. Mechanical calculators converted elevation angle to altitude.

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LUFTWAFFE FLYING BELOW CH RADAR BEAM

1. Chain Home Low (CHL) Radars added (1939 - 1940

2. Picked up Luftwaffe flying below CH radar beams

3. Operated at 180 – 210MHz

4. Antenna broadside 32 dipole array

5. Horizontal Beam width 200

6. Antenna steered on pedal crank by WAAF

7. “A” Scope display. PPI introduced in 1940

8. Antenna rotated at ~ 1 to 2 rpm

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CHAIN HOME GCI RADAR ADDED

1. GCI = Ground Control Intercept

2. 500MHz –600MHz GCI Radar introduced in 1942

3. Peak Power 50kW PW 4µs Rep-Rate 500pps

4. Antenna beam width ~4.50 Hor. And 7.50 Vert.

5. On 200’ tower detect bombers flying 500’ at 120miles

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IDENTIFICATION FRIEND OF FOE IFF (Secondary Radar)

• PASSIVE REFLECTOR

• MARK I

• MARK I I

• MARK I I I

• MARK X

THIS SLIDE IN WORK

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BASIC RADAR TYPES

CW DOPPLER RADAR

PULSED RADAR

PULSE DOPPLER RADAR

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CW DOPPLER RADAR

CW MICROWAVE TRANSMITTER (3cm 10GHz)

Compares Transmitted Freq to reflected signal frequency from moving objects to get Doppler shift frequency. Radar sees only moving objects

Aircraft: GCA operations. Approaching aircraft speed determined from Doppler shift

Road Traffic: Police Radar. Traffic speed determined from Doppler shift

Meteorology: Sees moving cloud masses etc.

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PULSED RADAR

• Surveillance Radar (Surface and air search)

• Precision Tracking Radar. Provides accurate Az El and Range information for:

a. Ground Control Approach GCA

b. Military Fire Control and Gun Laying Radars

• Satellite Tracking Radar (Sat. have Transponders)

PROVIDES: Range - Azimuth- Elevation Information

USED FOR:

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PULSED RADAR SYSTEM

BASIC PULSED RADAR SYSTEM

Timer is sometimes regarded as a Synchronizer

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PULSED RADAR DISPLAYS

• PPI Scope: Most popular display

• Provide maplike display in Azimuth and Range

• Polar coordinates: Range centre outward Azimuth 0 to 3600

PPI: PLAN POSITION INDICATOR

N

W E

S

G0MDK 27US NAVY SC RADAR CONSOLE

Probably USN Radar Operator’s School

G0MDK 28REPORTING RADAR SIGNAL STRENGTH

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PULSED RADAR TRANSMITTER

RADAR TRANSMITTER (MAGNETRON)

PFN charges up to 12kV (dc resonance Choke L and PFN C)

Energy stored in PFN = ½ V2C In this case 2 Joules.

Thyratron discharges PFN in 2µs which is stepped up to –27kV pulse

2 Joules of energy used in 2µs represents 1.0MW pk pwr input to Maggy

With pulse rate = 400pps, Duty Cycle = 2/2500. Average pwr. = 800W 00W

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PULSED RADAR TRANSMITTER COMPONENTS

•

HYDROGEN THYRATRON VX2511

VX2511

Pk I 350A Ave. I 350mA Max V 20kV**

** Hold off Voltage

Used with 500kW Radars

X BAND MAGNETRON (2J36)

Pk I 12A Pk V 14kV Pk Pwr 17kW Freq. 9.1GHz

L-Band Magnetron (5J26) tunable

Pk ~ I 35A Pk V 27kV Pk Pwr ~900kW Freq.~ 1.25GHz Z = 800

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PULSE DOPPLER RADARS

DISTINGUISHES BETWEEN FIXED & MOVING TARGETS

Surveillance Radars (Surface and air search)

Precision Tracking Radars

Relies heavily on digital signal processing (dsp)

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PULSE DOPPLER RADARS

SIMPLIFIED WEATHER RADAR SYSTEM

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MOVING TARGET INDICATOR (MTI)

STALO: Stable Local Oscillator

G0MDK 34MILITARY RADARS

US Navy 10cm Radar Surface Search SG-1b

BMEWS Radar Antenna

Navy Destroyer Escort Mast

USN Fire Control Radars

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US ARMY WW2 RADARS

AN/TPS-1B Range & Azimuth

Air Search Radar

Developed by Bell Telephone Labs

Produced by the Western Electric Operated by crew of two

Detects bombers alt 10k at 120 nmAN/TPS-10A Height Finder

Developed by MIT's Radiation Lab

Produced by Zenith

Operated by crew of 2

Detected bombers alt. 10k at 60 nm

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MILITARY RADAR STATION

L Band Search Radar Type: TPS-1B Freq. 1.2 – 1.3GHz Power output 500kW Range: 120nm Pulse width: 2µs RAF service Type 60

X-Band Height Finder Type: AN/TPS-10D.Freq : 9230 - 9404 MHz.Power output: 250kW Range: 60/120 miles. Pulse width : .5 & 2µsRAF service Type 61 Mk2

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GCA RADAR (Ground Control Approach)

Gilfillan

Freq: 9,000 - 9,160 MHz

Pulse Rep. Freq. (PRF): 1,500 Hz

Pulse-width: 0.18 to 0.6µs

Peak Power: 150 kW

Displayed Range: 40 nmi

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MILITARY HEIGTH FINDER

Military AN/FPS-6 Height Finder

Frequency:2600 - 2900 MHz

(PRF):300 - 405Hz

Pulse-width (PW):2.0µs

Peak Power:2.0MW

Displayed Range:300nm

Range Resolution: 1000ft 

beamwidth:  3.2 degrees Az 0.9 El

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AIRPORT RADAR

ASDE (Airport Surface Detection Equipment

Scans Airport Surface to Locate Vehicles and Aircraft

Limitation due to RF Multipath and Target ID problems.

Frequency 10GHz

Antenna Rotates at 60 RPM

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AIRPORT RADAR

Detects Aircraft and Weather Conditions in Airport Vicinity

Detection Range out to 60 Miles

Digital Airport Surveillance Radar

Primary Radar Frequency 2.7 – 2.9GHz

Peak Power 25kW

Secondary Radar (IFF) Top Array

Interrogator Frequency 1030MHz

Aircraft Transponder Freq. 1090MHz

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US NAVY RADAR

US Navy Air Search Radar

SPS-49A (MID 1990’s)

Frequency 850 – 942MHz

Antenna Size 8 X 24 ft.

Stabilized in Pitch and Roll

Beam width 3.30 Az 110 El

Parabolic CSC2

Rotation Rate 6 or 12 rpm

Peak Power 360kW

Development began in the 1970’s by The US Naval Research Lab

Latest Version Determines radial speed of each Target

Uses Unique Digital Signal Processing Developed by the NRL

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G0MDK 42

POLICE RADAR

K Band Speed Gun

Range 3500 feet

Locks on Target

3 Digit MPH or kmH Display

DECATUR $1250

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FLAT ARRAY ANTENNAS

Used in MIG29M2 NIIP BARS 29 Radar

Phased Array Electronic Steering

Scans and Tracks Multiple Targets

Considerable Losses in Phase Scanning

Used in MIG29 Zhuk-ME radar

Flat Slotted Array Antenna

Requires Mechanical Steering

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ACTIVE ELECTRONIC STEERED ARRAY

Array APG-81 AESA (X-Band)

Picture Shows Grumman Test Bed

2000 TR Modules ($2,000 each)

Total cost of Antenna $2,000,000

AN/APG 79 AESA Radar

Fitted on USN F/A-18E/F Super-Hornet

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Thank you for viewing my Radar Presentation

I hope you found it informative and enjoyable

Chuck Hobson G0MDK .

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