Hello to all,
the Radar was absolutely vital for Malta and so for Suez and so for the World. Some details must be explained.
from mid July 1942 RDF (CHL) were jammed. But it seems that GCI has been received. We can consider that the frequency of the CHL like AMES typ 2 was 200MHz but the frequency of the GCI should be 500-600Mhz (if it's GCI typ 11 ordered in 1942 or Fighter Direction like Mk1 yhat was mobile.
For type 11 Output Device is NT99. Mobile sets as standby if the 200MHz band was jammed. 600MHz was used by Germany.. Later versions from Mk5 Were coherent. First versions had rotary spark gap modulator. Horizontal beam 4 Deg, Vertical 11 Deg.
Other possibility : some CHL produced at 250-300Mhz as an insurance against jamming.
remark: The delivery of a centimetric surface radar (CD or GCI) should be impossible before September 1942.
Chronicle :
On July 1942 RDF were jammed (see the Malta diary also Malta Story). RV Jones in charge of the countermeasures has analysed the situation and recommended to go on transmitting even if the Radars are jammed. It's said that the jammers were stopped by the Germans because they've stopped to jammed seeing always the radar signals. But RV Jones memories are not totally exact. It was important to decoy the Germans by transmitting on 200Mhz as the same time the new GCI radar recently arrived on Malta was able to guide the Beaufighter AI mk 4 (200MHz) and then should certainly have other frequencies;
other important information that after the arrival of the hero of Dunkirq and the hero of the battle of Britain Air Vice-Marshal Keith PArk at Malta July 15, 1942). Park knew a lot about the radars and particularly the inefficiency of the RDF during the battle of Britain. Like on September 1940 he has hopefully changed the tactics, on the July 1942, Park changed the orders: the spit and beau have to take off as soon as possible to intercept enemy fighters and bombers on the way yo Malta, soon after they were detected.
Some RN escort vessels may be used the typ 271 radar to detect with their unjammed 3GHz frequency.
AI mk 4 radars of the beaufighters were impacted by the jammers. during 15 days before the arrival of USS ohio, the squadron 89 has won no victory (the last was Nevil Reeves' victory on the July 30/31 see
http://www.cieldegloire.com/sq_raf_089.php). On the 10th August 1942, the Canadian Ace Robert Fumerton has an engine problem and jump in the water. he was saved after some hours in the bath by another ace Nevil Reeves (who used many gallons of the precious oil to save his friend).
On the June 22, 1942 radar operators specially trained for AIMk7 use arrived from Egypt. (where Park has managed the arrival of the first squadrons fitted with AI mk7 radars for Beaufighters and ASV mk 3 radars for Wellington (squadron 248 and 252).
In the book "Chance and Design: Reminiscences of Science in Peace and War' written by Alan Hodgkin (specialist of the AI radars he's invented the scanning method for AI mk 7/8 radars), this one has detailed the arrival of the centimetric radar just before the Pedestal vital convoy.
On 14 beaufighter available 5 were sent to Malta. AI mk 7 were dismounted before. the Ai mk 7, the spares (lifetime of the 3GHz magnetron were only some hours at this date for 6-7kW), the personal for maintenance were transported thanks to two Sunderland.
Two beaufighter were operational to defend the USS ohio with 3GHz radars. Fumerton has taken one of the new beaufighter IF S/N V8268 who was modified to be fit with Ai Mk 7 radar at the Telecommunications Flying Unit (TFU).
The Santa Maria miracle : everybody knew how vital was USS ohio for the issue of the war) but nobody knows that the injured tanker helped by RN destroyers was saved during the August 14/15, 1942 night by radars.
At the end of the August 14, 1942, 15 Italian bombers (leaded by col. Ravazonni, one of the best pilot of the Italian air forces) took off from Sicily with very efficient torpedo. Park was warned by radars operators (some radars like GCI or ChL modified could be not jammed or RN centimetric radars).
Park has phoned from AHQ to squadron 89 and asked for Reeves and Fumerton to take off immediately ("there's a little job to Comiso" he said, Comiso was an Sicilian Airborne. guided by 'unjammable' GCI other RDF transmitting to decoy the jammers, the two beaufighters shot down two italian bombers near to attack the USS Ohio. Thos one was flanked with two destroyers (and after one) and towed by another one succeeded with spitfire and guns protection to enter in the harbour at 8 on the morning.
