RADAR SYSTEMS - Section B

286 TYPE

This was the first British small-ship radar developed from an airborne set, the RAF ASV Mk AII.

In January of 1941, Canadian destroyers serving with Western Approaches Command were being equipped with this set. It was fitted as a stopgap measure to provide some form of radar to detect surfaced U-boats at night, assist with station keeping, coastal navigation and aircraft warning for destroyers. The 286 went into production in the summer of 1940. Although inferior to daytime optical detection, the 286 improved detection tremendously in inclement weather or at night and was the best available set in that year. An Admiralty summary in May of 1941, noted that the chief merits of this set were its availability in quantity, its compact size and the speed of installation. The chief defects of the set were low range, high top weight for small craft and a poor sense of target discrimination.

This set operated on 214 megacycles (1.4 metres) at a power output of 6 kilowatt's peak, keyed by pulses 2 microseconds in duration. Its greatest fault was a fixed antenna system which consisted of two six element Yagi antennas,. These were paired vertically to produce three broad fixed beams for surface detection and warning over 60 degrees on either bow. Since the antenna was fixed, bearing accuracy was poor but it was still possible to resolve a target to plus or minus ten degrees in spite of this. Due to the fixed antenna, the ship had to be turned to acquire a different search sector.

Sea trials indicated that the set could detect a cruiser at six to eight miles, a destroyer from four to seven miles, and a trimmed down submarine at one to one and a half miles. Range accuracy was 200 yards between 1,000 and 20,000 yards. Under actual operating conditions, a trimmed down submarine could only be detected under the most optimum of conditions.

286 Antenna (Photo courtesy of Radar at Sea)

Aerial outfit ATQ was a non-rotating, fixed rectangular frame, supporting a forward facing Yagi array for transmission and  2 Yagi arrays angled outwards for beamswitched reception.

Type 286PQ had same the same aerial as Type 291, with only manual rotation, giving a beamwidth of 35°.

Type 286PU had one forward facing Yagi at top of mast for transmission and two angled Yagis below for beamswitched reception giving a fixed forward cover beamwidth of 140 degrees.

Type 286W/PW had a frame aerial mounted on a telescopic mast between the periscopes in submarines.

Displays: All types had 'A' scan.

Modifications: Type 286M was first operational naval version, P and Q variations had improved transmitters and directional aerials. PU was developed for trawlers and PW for submarines.

This set was the replacement for the 286 and was designed right from the beginning as naval set. It had a peak power output of 100 kw, a range accuracy of 35 yards on a 30,000 yard scale and a bearing resolution accurate to 3 degrees. Of note, was its brief service life from 1941 to 1942 before being replaced by the 291 set.

This was the final British 214 Mcs (P-Band) small ship, air search radar that was introduced in 1942. Early versions of this set required separate transmitting and receiving antennas, but a TR box was soon developed. The antenna was similar in concept to that of a 281 type, but the dipoles were supported by an X-shaped structure. This antenna had a beam width of 40 degrees and was of the lazy 'H' construction. Power output was 100 kilowatts at a pulse length of 1.1 microseconds. PRF was 500 Hz. It had the capability of detecting a bomber at 15 nm.

By 1944, type 291 was fitted to nearly all British destroyers and lesser escorts. Its installation time was seven days. The M, P and Q versions had power rotation for the antenna and PPI displays in addition to the 'A' scopes. Type 291U, developed for coastal forces and trawlers, had a special lightweight aerial consisting of a pair of superimposed Yagis. It could detect a submarine at 1.5 nm. Another variant, the 291W, was designed for submarines with a rotating aerial that had to be watertight and withstand hydrostatic pressure.

Eventually, the 291U and W sets were replaced with the model 267W. As for the 291, it remained in service in destroyers until about 1952 after which destroyer air search was restricted to coverage provided by the 293 set, the target indication radar.

Both the 291 and 293 sets were fitted on HMCS Haida simultaneously. Les Taylor of Walsall England, a former radar mechanic on Haida, recalls the details of the fitting. "The 291 office was located on the flag deck below the bridge. The antenna, which was located at the top of the foremast was fed by pyrotenax cable. This coaxial type cable consisted of a centre conductor surrounded by a powdered, ceramic-like compressed insulating material. The copper conductor and the insulation was enclosed within a hollow copper tube. If, for any reason, moisture entered the cable, its insulation properties fell below acceptable limits and required the occasional treatment with a blow torch to drive out the moisture.

Apart from these and other radar sets, I was also responsible for a new navigation aid called the QH3. It was developed by the RAF and later, its two military designers formed the DECCA Navigator Company. The QH3 was fitted while Haida was in Plymouth in 1944 and was housed in the chartroom, directly below the bridge. This set used a triangular transmission system that was reputed to fix our position to within a cable length. The QH3 became known as the QM set in the Royal Navy after 1945.

During my service on HAIDA, I was solely responsible for maintenance, range calibration, and repair of the radar equipment. There was no one that I could turn to for help, advice or to discuss technical problems. Slightly short of my eighteenth birthday, and being the youngest person aboard, I was supposed to be the expert. The technical radar school at HMS Valkyrie on the Isle of Man had many rooms containing radar equipment for either large or small ships. We were given a training choice on particular radar types that were fitted on large or small ships. Afterwards, we were drafted to those particular ships upon the completion of our training. I chose small ships. How lucky".

291 Antenna. (Photo courtesy CB 4182/45 Radar Manual via Øyvind Garvik)

This type was an S-band target indicator (sometimes referred to as 'Warning Combined' type) using the same transmitter as the 277 type and was equipped with the new, azimuth stabilized, 'cheese' antenna. It acquired that name because it looked like a block of cheese cut in half. Stabilization was necessary otherwise, the roll of the ship would tilt the 'fanned' beam and air targets might be displayed at wildly wrong bearings. The beam was wide in the vertical plane so that the ship's roll would have little effect. Typical detection range was 15 nm for an aircraft at 10,000 feet. Type 293M, which incorporated an 8 foot antenna, was introduced into service in 1945. 293P was similar to the previous model but it was modified for easier maintenance. A post-war radar program introduced the 293Q set with a redesigned 12 foot antenna. HAIDA was fitted with the 293 type until the late 1950's.

In Korea, 293 radars were operated in accordance with an Electronic Emission Control (EMC) policy. This meant that the radar could be turned on for a 3 minute duration for every 15 minute interval since the 293 was detectable by warning devices. It was assumed that the Koreans had such devices so the 293 sets were used for short periods of time only. High Definition Warning Sets (HDWS) radar was not detectable and required no such precautions.

293 Antenna (Photo courtesy of the British Admiralty)

The 293 radar system first saw service in 1944 and HMCS  HAIDA was fitted with the system soon thereafter. This system was a 10 centimeter,  S-band target indicator radar sometimes referred to as 'Warning Combined' (WC) type.  It employed a circular, sweeping display known as Plan Position Indicator (PPI). Operating at power levels of 500 kilowatts, the radar set had a typical detection range of 15 nautical miles for an aircraft flying at 10,000 feet. (Photo by Jerry Proc)

293 Target Indication Office. Items in this view: 1 - PPI Display 2 - Mirrors for projecting optical bearing lines onto the face of the PPI. 3 - Hand wheels for operating the optical system and transmitting bearings to out position 4 - Aerial bearing indicator. (Photo courtesy CB 4182/45 Radar Manual via Øyvind Garvik)

The bottle transmitter (B.T.) did not emit any radio frequencies. This device was used to provide transmission to a group of repeater motors, such as those in a radar installation, or to step up the number of repeaters that can be controlled from a gyro-compass where it is inconvenient to use a multiple transmitter or transmitter panel. They were also used extensively where it was desired to use Admiralty type equipment controlled by some other type of gyro compass.

Bottle Transmitter. (Photo courtesy of the British Admiralty)

Bottle transmitters fell into two groups -- pattern #5356 that transmitted to M-type repeater motors and pattern #5355 that transmitted to Sperry-type repeater motors. The B.T. could operate a load equivalent to fifteen Mark 10 M-type repeater motors at its maximum. On HMCS HAIDA, the bottle transmitter was used to transmit azimuth information from the Admiralty Mk 5 Gyrocompass to remote indicators.

The Range-Azimuth Indicator AN/SPA-4 was a self-contained unit that was designed for operation with any naval search radar system having a pulse repetition frequency between 140 and 3,000 pps. This indicator was capable of receiving radar information from one of eight different radar systems as selected by a front panel control. This feature was not used in HMCS HAIDA but ships of succeeding classes did use it. That switch controlled a radar switchboard called the SB-440.  Position 1 selected the SPS-10, 2 for SPS-12 and 3 for Sperry Mk2. On HAIDA there was an externally mounted selector switch that was used to select the radar input source. The SPA4 employed a remote PPI type indicator using a 10 inch, flat CRT.

Azimuth was determined by means of a mechanical cursor coupled to an electronic cursor jointly they were accurate to within one degree. Azimuth information was also indicated by a mechanical counter when the cursor was moved. Range information was obtained from range rings that could be displayed at intervals of 0.5, 1, 2, 5, 10, 20 and 50 miles. Range could also be measured by a mechanical counter. An electronic range strobe was accurate to within 1 percent of the maximum range being viewed.

The SPA-4 was also capable of transmitting electrically, the bearing and range information to other systems such as fire control or directly to a projector on the plot table. That would cut down on verbal communication.

When HAIDA was paid off, she was equipped with two AN/SPA4A units. One was located in the radar hut and the other unit was on the bridge.

An X-band fire control radar for AA guns. The antenna was a 40 inch diameter dish that could produce a 2.4 degree beam. Power output was 25 to 30 Kw with a range of 25,000 yards. HAIDA was fitted with the AN/SPG-34 fire control radar.

AN/SPG-34 installed on Nootka's 3"50 gun. Taken  in 1958. (Photo courtesy Gary Pollock)	The rear view of the SPG-34 radar as fitted on a 4 inch gun.
Side view of the SPG34 as fitted on HAIDA's 3"50 gun. (Photo by Jerry Proc)

Normally the SPG-34 radar was mounted on the right side of the 4 inch gun but here is a rare example of a left hand mount. This gun is located in a park in Trenton, Nova Scotia. (Photo by Sandy MacClearn)

SPG-34 electronics. (Photo # DNS-24595 courtesy DND, Canadian Forces Joint Imagery Centre provided via by Robert  Langille)

An Italian designed surface search radar that could transmit both short and long pulses at the same time. It was fitted to the 280 class ships in their original configuration. The antenna was a Cosecant-squared parabolic mesh.   Sometimes people associate the SPQ-2D with having two antennas. The "second antenna" in the AN/SPQ-2D radar is actually the Mk XII IFF interrogator antenna associated with that radar.

This set alternated the long and short pulses, receiving the transmitted RF returns in the (PRF limited) range prior to transmitting the next alternate pulse. Short pulse was used for close-in targets (giving minimum surface ranges), while LP was for longer surface distances and the "air coverage". The advantage with this process was you either selected SP or LP, and the video for the "alternate pulse returned video" was blanked on the video channel you were looking at - so you were only looking at half the video sweeps on the PPI. The receiver also had a "Dickie Fix" setting which could be switched in or out. This was a technique developed by R.H. Dickie which reduced the possibility of overexciting an I-F strip.

The Manufacturer was Signalamento Marittemo eo Aero of Florence Italy. The SPQ-2 was removed in the TRUMP modernization program.

For anyone who is interested in knowing more about Dickie Fix, here is a quote from the book "Introduction to Radar Systems" by Merrill L. Skolnik, 1980, pages 549-550

Impulsive noise, that can shock-excite the narrow-band radar receiver and cause it to ring, can be reduced with the Lamb noise-silencing circuit, or Dicke fix." This consists of a wideband IF filter in cascade with a  limiter, followed by the normal IF matched filter. The wideband filter is designed to include most of the spectrum of the interfering signal. Its  purpose is to preserve the short duration of the narrow impulsive spikes. These spikes are then clipped by the limiter to remove a considerable portion of their energy. If the large noise spikes are not limited and are allowed to pass they would shock-excite the narrowband IF amplifier and  produce an output pulse much wider in duration than the input pulse. Therefore the interference would be in the receiver for a much longer time and at a higher energy level than when limited before narrowbanding. Desired signals which appear simultaneously with the noise spike might not be detected, but the circuit does not allow the noise to influence the receiver for a time longer than the duration of a noise spike. This device depends on the use of a limiter. Limiters, however, can generate undesired spurious  responses and small-signal suppression, and reduce the improvement factor  that can be achieved in MTI processors. It should therefore be used with  caution as an ECCM device. 1f incorporated in a radar, provision should be included for switching it out of the receiver when it does more harm than  good.

The radar set AN/SPS6-C was a shipborne, long range, air and surface search type designed to supply target bearing and range data to its five inch A-scope indicator. In addition, as many as four, external, PPI indicators of the Radar Indicating Equipment VE, or Radar Repeater Equipment VJ or VK types could be attached to the SPS-6C. The RCN called this system WA meaning Warning Air. In 1947, the SPS-6 was granted AN nomenclature and the initial sets were procured from Westinghouse by the US Navy. Following quickly in 1947 were the 6A and 6B variants. The 6C and 6D versions were introduced in 1951, and the final 6E model in 1964.

The antenna was a unidirectional, parabolic type reflector, equipped with a wind balancing vane and had a characteristic 30 degree cosecant pattern in the vertical plane. Horizontally, the beam width was 3.5 degrees. Its rotational period was 5 to 15 RPM in automatic mode and up to 2.5 rpm in manual mode. A dual feed horn on the antenna transmitted and received both radar and IFF signals. Overall weight for the antenna and its mounting pedestal was 924 pounds. The antenna itself weighed 591 pounds. Contrast that with the weight of the system cabinet which tipped the scales at 1,063 pounds.

During the life of this system, there were four major American procurements. The first two were awarded to Westinghouse of Baltimore Md, the third went to AVCO Mfg/Crosley Division of Evandale Ohio and the final procurement was given to Stromberg- Carlson of Rochester, New York. Quantity and years of procurement by the RCN are not known at this time. HMCS HAIDA was fitted with AN/SPS-6C at the time she was paid off. It was originally fitted on her second tour of duty to Korea.
 
 

This image illustrates all the components of the AN/SPS-6C radar system.  Click to enlarge. (Photo courtesy Westinghouse Electric Corporation)

 

As of April 2003, this SPS6C was still employed as a research tool by the Institute of Tele- communications and Electronics of the Italian Navy in Livorno, Italy. (Photo courtesy of Alan Richardson, Eurocopter Deutschland GmbH)

For a detailed look at the SPS6-C components, please select this link.

AN/SPS-10B (Modified)

The AN/SPS-10B (modified) was a medium range, C-band, good definition, surface warning set with a limited air capability. In the Canadian Forces, this type was used in pre-DELEX steamers and training facilities. It was used for the detection, ranging and tracking of surface contacts and to a limited extent, air contacts as well. Range and bearing information was passed to a PPI type display. This radar type had the potential to be used with IFF/SIF equipment so the SPS-10 was originally fitted with a built in beacon. The RCN never used this feature, so it was disabled. There never was a model SPS-10A.

SPECIFICATIONS
 
 

Frequency	5450 Mcs variable to 5825 Mcs
Wavelength	5 cm
Peak power output	Short pulse = 190 kw; long pulse = 280 kw
Pulse Width	Short range pulse - .25 microsecond
	Long range pulse - 1.3 microsecond
PRR	625; variable to 650
Receiver IF	30 Mcs
Antenna rotation	15 rpm fixed
Beamwidth	Vertical - 12 to 16 degrees
	Horizontal 1.5 degrees
Resolution	On short range - 50 yds
	On long range - 275 yds
	For Bearing - less than 1 degree of error

 

SPS10 antenna. (Photo courtesy of http://www.fas.org)

Deliveries of the SPS-10 to the USN began in October of 1953. It was considered so effective in ASW operations that 25% of all ASW vessels were fitted with this set by the end of 1956. As late as 1976, this type was described as the most reliable surface search radar with a Mean Time Between Failure (MTBF) of 150 hours and a 6 hour Mean Time to Repair (MTTR).

AN/SPS-12

Radar set AN/SPS-12 was an L-band, medium surveillance radar designed to detect aircraft and surface vessels. It was primarily an air search set and was fitted on the original Canadian DDE class destroyers. In some circles, it was described as an SPS-6 with much greater capability. Target range was presented on an A-type indicator. Bearing data was also provided for presentation on PPI units. Provision was also made to connect IFF equipment to the radar set.

The late Dr. H. W. Smith of the Canadian Naval Technical History Association offers some background on the SPS-12.  "Perhaps surprisingly, the SPS-12 was not regarded as an improvement on the SPS-6 when first fitted in the fleet. In 1960-61, the Flag Officer Atlantic Coast and the Vice Chief of the Naval Staff (Admirals Dyer and Brock) became very concerned about the problems being experienced with fighting equipment in the RESTIGOUCHE class. The culprits named were, in order of importance:  the 3-inch/70 gun, the SQS-503 sonar and the SPS-12 radar. The source for this was:  Minutes and papers, 11th Senior Officers' Conference, November 20-21, 1961, file NSS 1279-188, now in the National Archives.

An investigation revealed that the radar equipment, unlike the gun and the sonar, to be blameless. The difficulty was the poor quality of maintenance in the fleet at the time. During this period one must remember that the trade structure of the Navy had been turned upside down in 1960 and electrical officers had been removed from ships, as a result of the Tisdall report.  In the short run, shipboard maintenance  suffered badly. Later on, the addition of a parametric RF amplifier (the Dicke-Fix receiver, developed at the Defence Research Telecommunications Establishment in Ottawa) greatly improved the performance of the SPS-12, and made it much less sensitive to mistuning then so common in the fleet".

Frequency range	1250 to 1350 Mcs
Range	: 200 miles
Wavelength	22.2 to 24 Cm
Peak Power Output	500 kilowatts
Pulse Length	Long pulse - 4 microseconds
	Short pulse - 1 microsecond
PRR	Long range - 300
	Short range - 600
	(Could be varied as an anti-jamming measure)
Receiver IF	30 Mcs
Beamwidth	Vertical - 30 degrees
	Horizontal - 3 degrees
Antenna rotation	Auto-clockwise; 2.5 to 15 rpm's
	Emergency - 10 rpm
First delivered	September 1953

AN/SPS-501

This was the AN/SPS-12 radar, adapted to the Dutch LW-08 antenna and fitted on 280 Class destroyers.

AN/SPS-502

A solid state upgrade applied to the AN/SPS-10 set. It was part of the Destroyer Life Extension Program (DELEX) carried out in the early 1980's which allowed Canada's surface fleet to remain viable until the new City Class patrol frigates were delivered. At the time, it was felt that this was necessary in view of the fact that North American tube production was winding down and the only sources of new tubes were from Eastern Bloc countries - a situation which was deemed unacceptable during the Cold War!

Nipigon's foremast sports the 502 and 503 radars  The upper radar is the Raytheon AN/SPS-502 surface search radar while the lower radar is the Marconi AN/SPS-503 air search radar. That's NIPIGON's badge on the SPS 503  platform . (Photo courtesy Haze-Gray site. http://www.hazegray.org)

AN/SPS-502 replaced the SPS-10 in at least HMC Ships  Annapolis, Nipigon, Terra Nova, Gatineau (excepting w/g, antenna, external cabling) on the east coast. All the various boxes of the SPS-10 radar system were stripped out and replaced by the one AN/SPS-502 Radar Transceiver cabinet in the Radar 1, with the remote in Ops.

The SPS-502 was a technician’s dream, because of the ample space inside the cabinet when it opened up for maintenance or repairs.

AN/SPS-503

 It was part of the Destroyer Life Extension Program (DELEX). See above photo, lower antenna.

The SPS-503 was a completely new radar based on the Marconi 820 air traffic control radar, slightly redesigned and marketed by Canadian Marconi as the CMR-1820.  It was a maintenance-intensive radar that was poorly suited to naval applications.  It’s TWTs ( travelling wave tubes) failed frequently, purportedly because the transmitter was designed for the continuous operation of an airport radar system as opposed to the frequent starts/stops of a naval radar. The failure-prone combat system was the bane of the radar techs.  But when it worked, it was the best long-range air search radar that the RCN had at the time.

The 503 was the Navy's first true digital TTL (tranistor/transistor logic) radar. There were literally hundreds of red LED fault indicators through out the various drawers in the cabinet and massive +5 volt power supplies. This radar allowed the Navy to gain experience on the basics of moving target indicator (MTI) techniques, signal processing  and use of travelling wave tubes as the final stage output amplifiers. Antenna was provided by Plessey.

AN/UPM-99

This was the IFF test set used aboard HMCS HAIDA and was used up until the phase out of the Mk X IFF system.

RTU

HAIDA was fitted with RTU during the mid 1940's. The acronym means Range Transmission Unit (M type system). It was used to transmit radar information to remote indicators on the ship.

SPERRY MARINE RADAR - MK 2

This was a medium range, surface search radar designated as a High Definition Warning Surface (HDWS) set. From the early 1950's, until well into the 1970's, almost every ship in the RCN was fitted with the Sperry Mk 2. Although its primary use was to locate other ships, helicopters, navigation aids and shorelines, it was very effective in detecting submarine periscopes. This type was fitted aboard HAIDA. After life expiry, the Mk 2 was replaced by the Sperry Mk 127E solid state radar.

Peak power	30 kilowatts
Operating frequency	9375 Mcs +\- 45 Mcs
Pulse length	0.25 microseconds
Pulse repetition rate	1000 pulses per second
Scanner rotation	15 rpm
Beam Width	Horizontal - 2 degrees   Vertical - 17 degrees
Range markers	Fixed 0.5, 2, and 5 mile intervals +/- 1%   Variable - 0.3 to 20 miles +/- 2%
Range scales	1, 2, 6, 15 and 30 miles
Resolution	Range - 80 yards   Bearing - 2 degrees
Indicator CRT size	12 inch diameter
Dimensions and Weights	Indicator - 27"D x 20"W x 51"H ; 350 lbs   Scanner - 20"L x 50"W x 49.5"H ; 300 lbs   Tx/Rx - 26.5"D x 22"W x 17"H ; 190 lbs   M-G Set - 36"L x 15"W x 12"D ; 330 lbs
Power requirements	115 VAC 60 Hz, 1000 watts
Contractor	Sperry Gyroscope, Great Neck, N.Y
Vintage	May 1953

 

This is the Sperry Mk2 PPI display as fitted in the Ops Room of HMCS HAIDA.  (Photo by Jerry Proc)

 
 

The Sperry Mk 2 antenna aboard HAIDA.  (Photo by Jerry Sullivan)

SPERRY 127E

A solid state navigation radar employing integrated circuit (IC) technology and first fitted aboard DDH 280 class.  Tribals. It used a 12 inch CRT and was designed on the precepts of the Radio Law, Safety Agreement of Life at Sea (SOLAS), the American FCC standards and the British DTI standards.

SPECIFICATIONS
 
 

Peak power	25 kilowatts
Range	120 miles
Operating frequency	9410 Mhz +\- 30 MHz
Pulse length	0.05 to 1.2 microseconds depending on range
Pulse repetition rate	500 to 4000 pulses per second depending on range
Scanner rotation	30 rpm for 1/4 to 6 mile scales   15 rpm for 12 to 120 mile scales
Dimensions and  Weights	Indicator - 27"D x 20"W x 51"H ; 350 lbs   Scanner - 20"L x 50"W x 49.5"H ; 300 lbs   Xcvr - 26.5"D x 22"W x 17"H ; 190 lbs   M-G Set - 36"L x 15"W x 12"D ; 330 lbs
Antenna	7 foot end fed, slotted array, waveguide type
Power requirements	115 VAC 60 Hz, 600 VA
Circa	1975- 76

SU

The SU radar was a WWII vintage USN type and was fitted aboard PRESTONIAN class frigates. Known for its good surface clutter rejection, it also had an A-scan for use as a gunnery spotting radar for the 4" gun and the maximum range mark was 80 miles. The radome for the SU is rather plain - roughly 4 feet tall and 2.5 feet in diameter, has a rounded top but just a little flat. Sixteen bolts clamp the radome to the base. Four or five cables and the waveguide come out the bottom, just off-center of the base, in the arc of a circle.

Type: Surface search shipborne radar
Operating frequency: 9085.5 MHz (X band)
Power Output: 50 kw
Pulse Lengths:  1/4 to 1 microsecond pulse
Initial Procurement by USN: Quantity 896
Year of procurement: 1944.

One photo of HMCS Algonquin 224 shows her fitted with the SU radar.
 
 

The SU antenna with the radome removed. (Photo via Denis Chouinard)

The SU radar is shown fitted on the foremast of a Prestonian class frigate. (Photo courtesy Sandy McClearn)

VK5 Radar Indicator

This was a radar display and one unit was installed in HAIDA's operations room. It had a 10 inch CRT and its primary feature was the ability to offset the sweep from the centre of the screen. The VK5 contained 101 vacuum tubes.

This is the VK5 aboard HMCS HAIDA. (Photo by Jerry Proc)

ADVANCEMENTS IN RADAR

Modern radar also provides excellent moving target indication by use of the 'Doppler shift' effect that a radio wave undergoes when it's reflected from a moving target. If the target is moving towards the radar, the frequency of the echo will be shifted upwards and vice versa. Traditionally, target detection is hindered by "clutter" echoes arising from echoes reflected from the ground, sea water or raindrops. Modern radar, with its higher transmitter power, higher frequency and more sensitive receiver, causes clutter to be even more pronounced so that even flocks of birds may show up on the screen. Antenna design can reduce these effects, and the use of circularly polarized waves reduces rain echoes. Coupled with a computer, the radar can be programmed only to display targets that are moving above a certain velocity. The wartime radar operator had to manually interpret the mass of data displayed on his PPI. In the world of air traffic control, as an example, the tracing of multiple targets would be impossible without the assistance of electronic processing. Progress toward satisfying this need had to await the arrival of large-scale integrated circuits, charge-coupled devices and the development of the technology for processing digital signals. Another important advance has been the computerized handling of video data, as in automatic plot extraction and track formation.

Radar engineers recognize that detection of a target still remains a matter of statistical probability, rather than certainty, in spite of all the great advances in components made since World War II.

---

Contributors:

1) LCdr. Patrick Smithers
2) Sandy McClearn <smcclearn(at)ns.sympatico.ca>
3) Øyvind Garvik <oygarvik(at)online.no>

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Jan 22/08