(This article may be found at http://www.combatsim.com/memb123/htm/2001/03/bob-rdf)

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Battle of Britain - RDF and the Strategy Game
By Len "Viking1" Hjalmarson

Game: Battle of Britain
Version: UK Release
Category: Air Combat Simulation (WWII)
Developer: Rowan Software
Publisher: Empire Interactive
Release Date: Released
Links:
[ Playable Demo ][ First Look ][ Preview ][ Pilot Career How-To ][ Flight Models in BoB ]
[ The Strategic Side of BoB ][ Creating Aircraft Skins in BoB ]
[ Ju-88 Gunnery in BoB ][ BoB Tutorial I ][ BoB Tutorial II ][ BoB Tutorial III ]
Article Date: March 23rd, 2001
Article Type: Strategy Guide


So you want to play the Battle of Britain's campaign, and you are ready to send out patrols for the RAF. Now you have to decide which patrols to send from where, and you want a Spitfire patrol. But where are they? Most of the Squadrons are composed of Hurricanes. How do you locate the aircraft you need?

You use an Order of Battle (OOB) of course. But where do you find an OOB for the Convoy phase, or for the next phase? Here, of course!



RAF Order of Battle



Now suppose you are flying for the Luftwaffe, and you are wondering just how far away the Chain Home Low stations will detect an incoming flight at 1000 feet? You need a map showing radar coverage. Here it is, all ready to go!

Before we give away all the goodies, let’s talk about detection in Battle of Britain, as well as about the historical systems that the RAF had in place.

RDF and the Observer Corps
Rowan's Battle of Britain models three detection systems, as well as the network that ties the systems together. The Chain Home system in 1940 consisted of twenty-one radar stations using fixed antenna arrays. Radio Direction Finding (RDF) was developed under the auspices of Hugh Dowding after a demonstration in February, 1935.


RDF Towers center and high



The system used aerials strung like nets between four masts. These had a range that varied with the altitude of the incoming aircraft. Targets at 1,000 feet could be detected up to 40km, 55km at 2,000 feet, 80km at 5,000 feet (1524 meters), and 133km at 13,000 feet.

The Chain Home system was augmented by thirty Chain Home Low stations. Chain Home Low used a rotating antenna atop a tower, transmitting a narrow beam that gave a capability against low-level targets. The range was much shorter and no height information was given. Chain Home and Chain Home Low stations were linked by telephone and passed plots between themselves as well as to the “Filter Room” at Fighter Command.

At the beginning of the Battle of Britain the Chain Home stations offered an average of twenty minutes notice of incoming raids. With Luftwaffe airfields as near as ninety-five miles at the Pas de Calais (notably JG26), this was a critical aid. The Luftwaffe had never come up against an air defense system of this sophistication.


RDF towers foreground and low



In addition to this system, RAF aircraft were fitted with rudimentary IFF transponders. Any radar signal returned by an RAF aircraft had a unique signature, and could be read as friendly by the RDF interpreters.

Complementing this detection system was the Observer Corps. Where the RDF system looked out over the sea, the Observers Corps looked to the rear and was responsible for tracking enemy air movements over the land. With over a hundred posts, the Observers made their observations with binoculars and telescopes, and used makeshift devices to establish bearing and estimate the height of enemy formations. These details, along with aircraft type, located within a series of 2km map squares, were then passed by telephone to the Group Headquarters. Each Group HQ had twelve plotters arranged around a grid map table on which enemy movements were plotted. Information from the Chain Home system and the Observers Corp together provided Fighter Command with an overall picture of the aerial war.


Hurricane in front of RDF tower



Rowan's Battle of Britain models this intelligence gathering system for the RAF. If you play the strategic game from the Operations Room, you will hear incoming calls and observe the changing plots on the strategic map. If some part of the system becomes inoperative, the map information will reflect the situation, become unreliable wherever information is no longer updated.

Following are links to two Orders of Battle. The first is dated July 7th, 1940. The second is dated August 1st, 1940. The later OOB reflects Squadron transfers and losses over the previous month. These OOBs are offered for 10 and 11 Groups only, since these are the Groups you will use the most.

LINK: OOB for 7th July, 1940
LINK: OOB for 1st August, 1940

Radar Range Maps
Next we have two maps. The first shows the coverage of Chain Home stations, and the second shows the coverage of the Chain Home Low stations. Click to bring up the larger images, then right click to copy and paste them to an image editing program or to your desktop.


Chain Home Radar





Chain Home Low



These maps work for you whichever side you fly on. If you fly for the RAF, you now know when you can expect to detect an incoming flight at both high and low altitude. If you fly for the Luftwaffe, you can see where the RAF will first detect your flight.

Of the two maps, the Chain Home Low ranges will become more important. Notice the bulge in detection range in the southwest. Planning an ingress to your target making which avoids this bulge will give the RAF the smallest amount of time to scramble fighters to an intercept.


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(This article may be found at http://www.combatsim.com/memb123/htm/2001/03/bob-rdf)