Tizard Mission Introduces Airborne Radar to the U.S.
SCR-540
SCR-520
SCR-720
AIA
AN/APS-6
-

The Tizard Mission, officially the British Technical and Scientific Mission, was sent to the United States in the autumn of 1940 for the purpose of providing the US military services with information on the various technical advances being made by Great Britain during the war against Germany. Members of the mission planned to brief the armed services on British advances being made in jet engines, rockets, and, most importantly, radar. The mission was headed by Sir Henry Tizard, chairman of the Great Britain's Aeronautical Research Committee and included Dr. E. G. "Taffy" Bowen, Britain's leading expert on airborne radar.

Tizard Mission brought two pieces of radar technology that were crucial in jump-starting the United States efforts in the future development of airborne radar. The first of these was the cavity magnetron. This highly secret device solved the problem of generating high power microwaves. Its disclosure to the academic community in the United States quickly led to the establishment of the government sponsored Radiation Laboratory at MIT. The laboratory's personnel were immediately directed to begin development of three important microwave systems: a 10 cm airborne interception radar, a 10 cm gun-laying director, and an electronic navigation system (LORAN). The second were examples of latest airborne radars in use by the Royal Navy and the RAF. In November 1040, a Mk IV radar was fitted to a Douglas A-20 at Wright Field and demonstrated to the Army Air Corps, which was so impressed with the system that plans to manufacture an equivalent radar set in the United States were immediately implemented.

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Tizard Mission Introduces Airborne Radar to the US
SCR-540
SCR-520
SCR-720
AIA
AN/APS-6
-

SCR-540 1.5m Radar

American Version of British Mk IV Radar. Manufactured by Western Electric, delivered 1942 for installation in USAAF P-70 (right) and Marine Corps PV-1 (lower right) night fighters. First confirmed combat kill April 19, 1943, 6th NFS, Guadalcanal.

Description

1.55 cm airborne radar for aircraft interception. Weight: 181 lb including cables and inverter. Operators: 1. Power: 40 amp, 27 volt DC. Antenna: fixed quarter wave dipole with directors on side of fuselage (azimuth receiving): 2 fixed quarter wave rods, one above and one below wing (elevation receiving). Indicators: 3-inch CRT with vertical baseline target pips on left and right (azimuth): 3-inch CRT with horizontal baseline, target pips above and below (elevation).

Performances Altitude Range Min Range Max
Bombers 20,000 ft 100 yd 6,000 yd
Fighters 17,000 ft 100 yd 4,000 yd
Accuracy : Range:100 yd Angular:10░ Elevation:10░

Search

Fixed antenna, targets within forward hemisphere 160░ elevation sector may be detected. Effective search range limited to altitude of plane.

Antenna Specifications

Bent folded dipole with director on nose of aircraft. Elevation receiving: 2 fixed quarter wave rods with directors, one above and one below the left wing. Lobe switching at 1750 cycles/min


Anntenna installation on A-20 (prototype P-70), left-to-right: elevation receiving antenna, transmitting antenna, azimuth receiving antenna
 
Transmitter Specifications    
Frequency: 193 mc/s Pusle Rate (pps): 750 to 850
RF Source: 2 710s push-pull Pulse Rate Beacon: 750 to 850 nps
RF Lines: Coax (solid dielectric) Pulse Legnth: 1.3 Ás
Pulser Type: Hard Tube Pulse Length, Beacon: 2.1 Ás
RF Peak Power: 10 kw Energy pp, Radar: .013 joules
RF Average Power: .01 kw    
Receiver Specifications    
Type: Superheterodyne IF Band Pase: 5 mc/s
Stages: O-RF; 4-IF Mixer: 955 tube
Local Oscillator: 955 Noise, db above kt df: 14-16
Intermed. Freq.: 30 mc/s    
       
       

Indication and Data Output

Operator has indicator with two 3-inch CRTs. Left tube has horizontal sweep with echoes appearing as pips above and below searching plane. Right tube operates similarly but has a vertical sweep with left and right pips indicating whether target is to the left or right of searching plane. Time scales are variable and the distance for a given length of trace depends on control setting. Scale is exponential. Attack range: 1-7 miles. Homing range: 100 miles.

Remarks

Maximum altitutde for satisfactory operation: Approximately 20,000 ft. Operates with SCR-640 homing beacon.
Generally not employed to control an area when prsence of enemy aircrft has not been determined in advance. SCR-540-T2 is similar to SCR-540-A except for minor circuit differences.

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Tizard Mission Introduces Airborne Radar to the US
SCR-540
SCR-520
SCR-720
AIA
AN/APS-6
-

SCR-520 10 cm Radar

Developed for installation on P-70.  Most SCR-520s were converted to SCR-517 for ASV.

Performances Altitude Range Min Range Max
Bombers 10,000 ft 125 yd 10,000 yd
Fighters 17,000 ft 125 yd 6,000 yd
Accuracy : ▒10░ full scale Azimuth ▒3░ Elevation▒3░
Manufacturer Western Electric  
Number Ordered 108    
Number Delivered 108    
Cost: Unit $17,765 Cost: Total $1,918,620

Search

Antenna spins at 360 rpm and searches the forward 180░ sector. While spinning, antenna tilts at rate of 30░/sec. between limit which can be set at -10░ to 45░, +20░, +35░, +50░,or +65░. Range: 1, 10, and 100 miles. Beacon operation on 10-.

Antenna specifications

Vertically polarized dipole in 30-inch paraboloid. Antenna sons at 360 rpm. As it rotates, the antenna tilts up and down at the rate of 30░ per second.
Half power basewidth: 10░ azimuth and elevation.
Gain: 340.

Transmitter Specifications    
Frequency: 3000 mc/s Pusle Rate(pps): 2000
RF Source: Magnetron Pulse Rate Beacon: 400 pps
RF Lines: 7/8 inch stub Coax Pulse Legnth: 1.3 Ás
Pulser Type: Hard Tube Pulse Length, Beacon: 2.5 Ás
RF Peak Power: 40-60 kw Energy pp, Radar: 0.05 joules
RF Average Power: .01 kw    
Receiver Specifications    
Type: Superheterodyne IF Band Pase: 4 mc/s
Stages: O-RF; 7-IF Mixer: 708A tube
Local Oscillator: 707A Noise, db above kt df: 19-21
Intermed. Freq.: 60 mc/s    
       
       
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Tizard Mission Introduces Airborne Radar to the US
SCR-540
SCR-520
SCR-720
AIA
AN/APS-6
-

SCR-720 10 cm Radar

Improved SCR-520 developed for installation on P-61 (right), P-70 and DeHaviland Mosquito.  Research and Development by Bell Telephone Laboratories

Wavelength and Function

10 cm radar for air search with beacon functioins and connections to IFF.

Similar in purpose to SCR-520-A and B, but components are smaller and lighter in weight. Manufactured by Western Electric.

Performances Altitude Range Min Range Max
Bombers 10,000 ft 100 yd 17,000 yd
Fighters 17,000 ft 100 yd 8,500 yd
Accuracy : ▒10░ full scale Azimuth ▒3░ Elevation▒3░

Search

Ranges: 1, 10, 20, and 100 statute miles. Azimuth Search: 180░ forward sector. Elevation Search: operator may select any one of 4 sectors: 0░ to 0░ (level), -5░ to +5░, +5░ to +20░ and +20░ to +50░.

In later models the ranges are changed to 5 miles, expanded sweep (dog leg), 10 20, and 100 statute miles.

Antenna specifications

Dipole antenna with 29-inch paraboloid reflector spinning at 360 rpm (2, 10, or 20 mi. radar) or 100 rpm (100 mi. radar or 10, 20, or 100 mi. beacon).

Half power basewidth: 10░ azimuth and elevation.  Gain: 340.

Transmitter Specifications    
Frequency: 3000 mc/s Pusle Rate(pps): 1500
RF Source: Magnetron Pulse Rate Beacon: 375 pps
RF Lines: 7/8 inch stub Coax Pulse Legnth: 0.75 Ás
Pulser Type: Rotary gap Pulse Length, Beacon: 2.5 Ás
RF Peak Power: 100-150 kw Energy pp, Radar: 0.08-.11 joules
RF Average Power: .0.112-.17 kw    
Receiver Specifications    
Type: Superheterodyne IF Band Pase: 3 mc/s
Stages: O-RF; 6-IF Mixer: Crystal (IN21)
Local Oscillator: 726A Noise, db above kt df: 11-15
Intermed. Freq.: 60 mc/s    
       
       
 

Indication and Data Output

Operator Station (far right): 1 5-inch CRT with type-B scan and 1 5-inch CRT with type-C scan.

Pilot's CRT (near right): 1 -3-inch type B (20 and 100 mile search and 10, 20, and 100 mile beacon), or type C (2 and 10 mile search).

Vertical scale on C-tube extends from -15&deg to +60&deg. C-tube shows only targets within limits of range dial setting. Pilot also has range meter.

Remarks

Equipment will operate under temperatures from -40░F to +122░F, with relative humidity as high as 90%.   Max.altitude for satisfactory operation: 30,000 ft.

SCR-520-B differs from SCR-520-A by the addition of beacon and IFF features and a 100 mile range.

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Tizard Mission Introduces Airborne Radar to the US
SCR-540
SCR-520
SCR-720
AIA
AN/APS-6
-

AIA 3 cm Radar

Air Interception Radar For Carrier Based Fighters for installation on F4U-2N (top right) and F6F-3N (bottom right) night fighters.

Wavelength and Function
3.2 cm radar for surface search and air interception. Provides beacon function and has connections for IFF.

Research and Development
by Radiation Laboratory and Sperry Gyroscope Co., Inc.

Operational Requirements
Number of Operators: 1
Weight: 242 lb. less cables
Power Supply: 25 amp, 27 v DC, and 700 w, 115 v. 1 ph, 400 to 2400 cps

Search
Spiral scan through 120░ cone ( ▒60░ from plane axis) at 15 scans per minute for 4 mile search and 100 mile operations. Conical with 10░ covered operation on "Sight."

Target Following
Aiming by pointing plane in conjunction with conical scan and aiming error indicator (Type G).

Antenna specifications
Rotating and nodding 17-inch paraboloid with waveguide feed.
Half power beam width: 4.5░ in azimuth and elevation - Gain: 1500.

Performances Altitude Range Min Range Max
Bombers 10,000 ft 150 yd 8,000 yd
Fighters   150 yd 7,500 yd
Battleships     30 miles
Accuracy : ▒10░ full scale Azimuth ▒3░ Elevation ▒20░

 
Transmitter Specifications    
Frequency: 9375 mc/s Pusle Rate(pps): 2000
RF Source: Magnetron Pulse Rate Beacon: 500 pps
RF Lines: 1Î1.1/8"waveguide Pulse Legnth: 0.5Ás
Pulser Type: Hard Tube Pulse Length, Beacon: 2.1Ás
RF Peak Power: 40 kw Energy pp, Radar: 0.02 joules
RF Average Power: .01 kw    
Receiver Specifications    
Type: Superheterodyne IF Band Pase: 2.6 - 4 mc/s
Stages: O-RF; 7-IF Mixer: IN23A crystal
Local Oscillator: 723A/B Noise, db above kt df: 16
Intermed. Freq.: 30 mc/s    
       
       
 

Indication and Data Output
3-inch indicator with type G scan with 0.5 nautical mile range for "Sight", type O (double dot) scan with 4 nautical mile range for "Search", and B scan for 100 nautical mile search and beacon range.

Manufacturer Sperry Gyroscope Company  
Number Ordered 750    
Number Delivered 604    
Cost: Unit $8,618 Cost: Total $5,205,272
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Tizard Mission Introduces Airborne Radar to the US
SCR-540
SCR-520
SCR-720
AIA
AN/APS-6
-

AN/APS-6 3 cm Radar

Lightweight Search and Intercept Radar. For installation in F6F (right) and F7F fighters.

Wavelength and Function
3 cm search and interception radar for carrier based aircraft. Provides beacon function and has connections for IFF, and provides suitable indication for firing guns. Major improvement over AIA was placement of modulator in nacelle close to scanner, which elimnated long wave guide runs that were difficult to install and maintain.

Research and Development by Radiation Laboratory and Westinghouse Electric and Mfg. Co., Inc.

Operational Requirements
Number of Operators: 1
Weight: 242 lb. less cables
Power Supply: 29 amp, 27 v DC, and 780 w, 115 v. 1 ph, 800 to 2400 cps

Search
Spiral scan through ▒60░ at 1200 rpm. Search ranges of 1, 5, 25, and 65 nautical miles. 1000 yd range for close approach and gun aiming. Beacon ranges: 1, 5, 25, and 100 nautical miles.

Target Following
Fixed guns are aimed by pointing plane.

Antenna specifications
Dipole in rotating and nodding 17-inch paraboloid.  Half power beam width: 5░ in azimuth and elevation.  Gain: 1100.

Performances Range Min Range Max Search Aiming Firing
Bombers 120 yd 10,000 yd      
Fighters 120 yd 8,000 yd      
Battleships   35 miles      
Accuracy:Range   ▒10░ +2░full scale 25 yd firing:250yd
Accuracy:Azimuth     ▒3░ ▒0.5░  
Accuracy:Elevation     ▒3░ ▒0.5░  

Transmitter Specifications    
Frequency: 10,000 mc/s Pusle Rate(pps): 2000
RF Source: Magnetron Pulse Rate Beacon: 500 pps
RF Lines: waveguide Pulse Legnth: 0.5Ás
Pulser Type: Hard Tube Pulse Length, Beacon: 2.0Ás
RF Peak Power: 40 kw Energy pp, Radar: 0.02 joules
RF Average Power: .04 kw    
Receiver Specifications    
Type: Superheterodyne IF Band Pase: 2.7 mc/s
Stages: O-RF; 7-IF Mixer: IN23 crystal
Local Oscillator: 723A/B Noise, db above kt df: 16
Intermed. Freq.: 60 mc/s AFC optional  
Separate Oscillator for Beacon AVC aiming only  
       
 

Indication and Data Output
3-inch indicator CRT: B scan on search and beacon ranges with type O scan on 1 and 5 mile search range. Type G scan for aiming.

Remarks
AN/APS- 6 uses Westinghouse RF head with radar and beacon AFC. AN/APS-6A uses Philco RF head and has no beacon AFC.

Manufacturer Westinghouse Electric  
Number Ordered 3129    
Number Delivered 2161 as of 8/1/45    
Cost: Unit $10,938 Cost: Delivered $23,632,696

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