RADAR Chuck Hobson BA BSc (hons). INTRODUCTION.
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.
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)
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.
S1/c Chuck Hobson Jan. 1945
US Navy Recruiting Poster 1944
US Naval Destroyer Escort DE-316
Typical Destroyer mast
THE EARLY BEGINNINGS
Chain Home Radar Transmitter Antennas
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)
Scientific Officer at the Radio Research Station
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**
ARNOLD WILKINS (1907 – 1985)
** 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
RAF Long Range Bomber
Prototype Flown in 1930
Speed 229km/hr (142 mph) Range 1480km (920 Miles) Ceiling 6400m (21000 ft.)
Deventry Experiment Site
Transmitted very broad beamto illuminate all aircraft in search area
Receiving antennas (not shown) provided azimuth and elevation data
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.
THIS SLIDE IN WORK
PULSE 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.
PROVIDES: Range - Azimuth- Elevation Information
BASIC PULSED RADAR SYSTEM
Timer is sometimes regarded as a Synchronizer
PPI: PLAN POSITION INDICATOR
Probably USN Radar Operator’s School
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
X BAND MAGNETRON (2J36)
HYDROGEN THYRATRON VX2511
VX2511 PkI 350AAve.I350mA Max V 20kV**
** Hold off Voltage
PkI 12A Pk V 14kV Pk Pwr 17kW Freq. 9.1GHz
Used with 500kW Radars
L-Band Magnetron (5J26) tunable
Pk ~ I 35A Pk V 27kV Pk Pwr ~900kW Freq.~ 1.25GHz Z = 800
DISTINGUISHES BETWEEN FIXED & MOVING TARGETS
Surveillance Radars(Surface and air search)
Precision Tracking Radars
Relies heavily on digital signal processing (dsp)
SIMPLIFIED WEATHER RADAR SYSTEM
STALO: Stable Local Oscillator
BMEWS Radar Antenna
US Navy 10cm Radar Surface Search SG-1b
Navy Destroyer Escort Mast
USN Fire Control Radars
AN/TPS-1B Range & Azimuth
Air Search Radar
Developed by Bell Telephone LabsProduced by the Western Electric Operated by crew of twoDetects bombers alt 10k at 120 nm
AN/TPS-10A Height Finder
Developed by MIT's Radiation LabProduced by ZenithOperated by crew of 2Detected bombers alt. 10k at 60 nm
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
L Band Search Radar Type: TPS-1B Freq. 1.2 – 1.3GHz Power output 500kW Range: 120nm Pulse width: 2µs RAF service Type 60
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
Military AN/FPS-6 Height Finder
Frequency:2600 - 2900 MHz
(PRF):300 - 405Hz
Range Resolution: 1000ft
beamwidth: 3.2 degrees Az 0.9 El
Antenna Rotates at 60 RPM
ASDE (Airport Surface Detection Equipment
Scans Airport Surface to Locate Vehicles and Aircraft
Limitation due to RF Multipath and Target ID problems.
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
Detects Aircraft and Weather Conditions in Airport Vicinity
Detection Range out to 60 Miles
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
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
K Band Speed Gun
Range 3500 feet
Locks on Target
3 Digit MPH or kmH Display
Used in MIG29 Zhuk-ME radar
Flat Slotted Array Antenna
Requires Mechanical Steering
Used in MIG29M2 NIIP BARS 29 Radar
Phased Array Electronic Steering
Scans and Tracks Multiple Targets
Considerable Losses in Phase Scanning
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
Thank you for viewing my Radar PresentationI hope you found it informative and enjoyableChuck Hobson G0MDK .