SCR-584 Technical Description

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		+	The SCR 584, development of which began in 1941, could be operated in either a search or track mode. In the search mode the antenna was rotated through 360 degrees at 6 RPM. On each revolution the antenna elevation is raised so that it reaches a maximum elevation of 20 degrees in one minute. The result is a complete helical search of the space surrounding the radar.
		+
		+	The collected information was displayed on a Plan Position Indicator [PPI] which allows the operator to see all the radar returns on a map-like screen with the radar at its centre. On the console there were also two J-displays, a coarse-range display and fine-range display. Having designated the target on the PPI the operator could cause the antenna to carry out a spiral scan around the selected elevation and azimuth, and could thus locate a target.
		+
		+	So we have three different scan patterns of associated with the antenna:
	[[Image:Helical scan.jpg|right|thumbnail|180px|Helical scan mechanism:<BR>''Image – ‘Electronics’; Fig 2, Dec ’45, p.104'']]		[[Image:Helical scan.jpg|right|thumbnail|180px|Helical scan mechanism:<BR>''Image – ‘Electronics’; Fig 2, Dec ’45, p.104'']]
-	'''Back to''' [[VERLORT Radar|Verlort Radar]]
-	<BR><BR>
-	The Verlort '''Plan Position Indicator''' (PPI) was driven by a '''mechanical''' computer. Once target acquisition occurred, the radar operator needed to keep a ‘hairline’ indicator manually centred on the target’s echo to maintain track.
-	Even more intriguing were the target acquisition techniques.	+	'''(a)''' a helical scan in which the antenna scans the sky around the radar;
-	For targets where only crude position information was available, a '''helical scan''' was used to acquire the target. The dish was swung in a circle at 6 rpm along as it moved with the reflector tilting to and fro about 4&deg; per dish revolution to create a '''helical spiral''' about 20&deg; wide along the expected track path - see 'Helical scan mechanism' diagram on right.	+	'''(b)''' a spiral scan in which the antenna is caused to spiral outwards from a designated azimuth and elevation and then back to the designated position until a particular target is located. This would be limited in extent, probably only 1 or 2 degrees maximum; and
		+
		+	[[Image:Conical beam.jpg|left|thumbnail|250px|A conical scan beam:<BR> ''Image – ‘Electronics’; Fig 1, Nov ’45, p.104'']]
		+	'''(c)''' the rotation of the beam around the bore sight line of the antenna so as to provide a conical beam pattern which allows the system to automatically determine the position of, and automatically track, the target.
		+
		+	Having located the target in angles the fine range display would then be used to differentiate between, for example a friendly fighter and enemy bomber and then allow the operator initiate automatic tracking of that target.
-	Where there was more certainty about the target path, a '''nutating scan''' mode was used. The slightly offset dipole feed was rotated rapidly to produce off-axis radiation increasing the effective beam width from 2.5&deg; to about 5.5&deg; . Nutation was switched off when the target was acquired. See the ‘conical scan beam’ diagram below left and the ‘nutating antenna dipole feed’ below right.	+	In the track mode the operator was required to adjust the rate of range change by operating a hand-wheel on the console. The Azimuth, Elevation, and Range analogue signals were fed to the external M-9 Gun Predictor. The M-9 was an analogue computer which solved the targeting problem and pointed the associated 90mm anti-aircraft guns so that the shell and the target arrived at the same spot simultaneously.
		+
		+	The angle scans, both the helical and the spiral, were generated by motor driven cams in the angle control panel. The caption on the photograph of the interior of this panel at www.hamhud.net/darts/scr584.html refers to the angle control panel as a mechanical computer in the PPI unit. The analogue computer associated with the SCR584 was the M-9, a separate device.
		+
		+	See: The Test at [www.infoage.org/sigcww2-test-p265-scr584.html] for a history of the set.
		+
		+	See: Tracking Systems at [www.fas.org/man/dod-101/navy/docs/es310/trksys/trksys.htm] for an explanation tracking systems
-	[[Image:Conical beam.jpg|left|thumbnail|250px|A conical scan beam:<BR> ''Image – ‘Electronics’; Fig 1, Nov ’45, p.104'']]
	[[Image:offset dipole.jpg|right|thumbnail|290px|Nutating antenna dipole feed:<BR>''Image – ‘Electronics’; Fig 5, Dec ’45, p.107'']]		[[Image:offset dipole.jpg|right|thumbnail|290px|Nutating antenna dipole feed:<BR>''Image – ‘Electronics’; Fig 5, Dec ’45, p.107'']]
		+
		+	----
		+
		+	These notes have been prepared by Ken Anderson, one time AN-FPQ6 radar supervisor at the Carnarvon Tracking Station

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Revision as of 05:51, 27 February 2008

The SCR 584, development of which began in 1941, could be operated in either a search or track mode. In the search mode the antenna was rotated through 360 degrees at 6 RPM. On each revolution the antenna elevation is raised so that it reaches a maximum elevation of 20 degrees in one minute. The result is a complete helical search of the space surrounding the radar.

The collected information was displayed on a Plan Position Indicator [PPI] which allows the operator to see all the radar returns on a map-like screen with the radar at its centre. On the console there were also two J-displays, a coarse-range display and fine-range display. Having designated the target on the PPI the operator could cause the antenna to carry out a spiral scan around the selected elevation and azimuth, and could thus locate a target.

So we have three different scan patterns of associated with the antenna:

(a) a helical scan in which the antenna scans the sky around the radar;

(b) a spiral scan in which the antenna is caused to spiral outwards from a designated azimuth and elevation and then back to the designated position until a particular target is located. This would be limited in extent, probably only 1 or 2 degrees maximum; and

(c) the rotation of the beam around the bore sight line of the antenna so as to provide a conical beam pattern which allows the system to automatically determine the position of, and automatically track, the target.

Having located the target in angles the fine range display would then be used to differentiate between, for example a friendly fighter and enemy bomber and then allow the operator initiate automatic tracking of that target.

In the track mode the operator was required to adjust the rate of range change by operating a hand-wheel on the console. The Azimuth, Elevation, and Range analogue signals were fed to the external M-9 Gun Predictor. The M-9 was an analogue computer which solved the targeting problem and pointed the associated 90mm anti-aircraft guns so that the shell and the target arrived at the same spot simultaneously.

The angle scans, both the helical and the spiral, were generated by motor driven cams in the angle control panel. The caption on the photograph of the interior of this panel at www.hamhud.net/darts/scr584.html refers to the angle control panel as a mechanical computer in the PPI unit. The analogue computer associated with the SCR584 was the M-9, a separate device.

See: The Test at [www.infoage.org/sigcww2-test-p265-scr584.html] for a history of the set.

See: Tracking Systems at [www.fas.org/man/dod-101/navy/docs/es310/trksys/trksys.htm] for an explanation tracking systems

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These notes have been prepared by Ken Anderson, one time AN-FPQ6 radar supervisor at the Carnarvon Tracking Station