Charles Debono, curator, National War Museum, Valletta
Radar stations during wartime Malta
Transmitter for Mark 1 gunlaying radar. The photo does not say where it was shot.
Bill Crawford (February 4) asked for information on No. 504 AMES Radar Station and similar stations in wartime Malta.
There is not much information about a particular station in wartime Malta. Period photographs do not seem to exist presumably because it was an important technology at the time.
Some photographs were possibly shot during the war, but due to strict censorship they do not contain any indication that the subject was AMES No. 504 at Dingli. The following is some information on the wartime radar system of Malta.
After several experiments, in December 1935, the British Government decided to install a five-station system called Chain Home (CH), covering approaches to the Thames Estuary. However, the name was immediately changed to RDF, meaning Radio Directing Finding.
In the meantime, as radar technology was in its infancy, in Malta, the British authorities decided to build an early-warning system, the Parabolic Acoustic Mirror known as Il-Widna (ear), constructed at Ta' San Pietru, Magħtab.
Il-Widna became outdated when the British government decided to install the first RDF in Malta. It is important to say that this was to be the first RDF installed outside the UK.
So, in March 1939 the first Air Ministry Experimental Station (AMES) No. 242 was mounted at Dingli Cliffs. By mid-July 1941 the number of stations was increased by three: No. 501 AMES at Tas-Silġ, No. 502 AMES at Madliena and No. 504 AMES at Dingli too (since Dingli is one of the highest points in Malta). The early RDF stations were Type GL. Mk. I and Mk. II
At this time the name was changed to COL (Chain Overseas Low) stations which had the role of plotting medium to low-flying aircraft, while No. 242 AMES at Dingli was a COH (Chain Overseas High) station which had the capacity of plotting high-flying aircraft.
The information received by the stations, which consisted of the approximate number of approaching aircraft (both Allied and Axis) and their height was passed to the Filter Room at Lascaris War Rooms.
The Filter Room would then pass the information to the plotters in the Operations Room where, on instruction, they would place counters on the grid references on a large map of the Central Mediterranean with Malta in the centre. This information would then pass to the RAF fighter to intercept enemy formations.
For an exact control of RAF fighters intercepting enemy aircraft, a GCI (Ground Control Interception) station was also mounted at Qawra Point as 314 AMES. More radar stations were afterwards set up: No. 241 AMES at Għar Lapsi (previously installed at Dingli in 1939), 841 AMES at Wardija and at No. 521 at Gozo Giordan Lighthouse. These RDFs consisted of AM.13/14 units.
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Pule' Carmel
Feb 12th 2010, 20:24
The high frequency valves in excess of 50 megs were Called ACORN valves, because they were actuallyshaped as an acorn where the distance the electrons had to move was shortened as much as possible. But even this design, what was considered as a Fast electron, this was relatively slow when it was required to oscillate at more then 50 million times per second. Hence the valve had reached its limits with a lot of whistling in electronic equipment. The injenuity of the engineers during the war, resulted in turning what was a disadvantage in a valve, to an advantage in a klystron. THe gap the electrons had to move in a valve was lengthened and more plates were put in between which interferred with the velocity of the electron during its travel from the cathode tothe anode. The remarkable wonders of a human brain is, that what brings with his back aganst the wall for one man is turned into anadvantage by another man, if only he thinks hard in the predicament he finds himself. Nowadays, not only canRadar tell you the position of many targets, it can tell you their velocity, accelleration and it will inform you about collissions.
Pule' Carmel
Feb 12th 2010, 19:47
The photograph seems to show the active component as a horizontal dipole in front of a reflector. Its length suggests that it operated at 200-400 Megacycles. It was suggested that the origin of the Radar, was not for identification of oncoming aircraft, but someone thought that launching high energy Radio electromagnetic pulses, they could stop the ignition system, hence spark plugs, of and enemy aircraft. Of course they could not, but were rather surprised at the fact that the aircraft REFLECTED the sent electromagnetic wave off the aircraft, hence they could tell its position but not whether it was friend or foe. For this reason when used in thick fog, the British shot many of their own pilots! Thus the self quenching super regenerative receiver was invented, put in Spitfires and before firing, the British Interrogated the craft overhead. If it was British, the super regerenative receiver would react at the interrogation, and so the gunners would not shoot at it. The Radar was first powered by valves( up to 100Megahertz then), then Klystrons, then the Magnetrons which surprised everybody with its power . I worked on this stuff and related equipment in the Royal Navy!
Galea. L
Feb 12th 2010, 16:31
http://en.wikipedia.org/wiki/Chain_Home Just made a google search and confirmed some information. The photo shows a CHL station operating around 200MHz which can be confirmed by the size of the aerial since COH operated on the shortwaves/low VHF area (20MHz - 50MHz). There is also another factor since the CHL stations used a rotatable antenna while the COH did not and the antenna shown in the photo seems to be rotatable. So the photo site could be limited to those places where it is known that this type of radar was set up, the probability being that it was in the highest places available especially if a particular sector was required to be watched. The Germans had their own Freya radar and other systems which they used to guide their aircraft to bomb particular targets http://www.economicexpert.com/a/Radio:navigation.htm As an aside, those interested in the Gloster Gladiator and other aircraft have a look at http://www.spitfirespares.com/SpitfireSpares.com/Pages/radio.html Other links http://www.radarpages.co.uk/mob/ch/chainhome.htm and do a google search using chain home
Galea. L
Feb 12th 2010, 15:48
Thanks for the information. I think that judging by the aerial size teh frequency was in the VHF region while the Chain Home stations in the UK were I believe on the high end of the short wave just below 30MHz (Mc/s at the time)
Joe Morana
Feb 12th 2010, 11:54
Good job, Mr Curator! A very informative and historic submission!