On the 4th, Kesselring had been asked for his decision on a proposal to use a 20 kW transmitter in Athens to broadcast spoof messages over RAF reconnaissance frequencies during major convoy operations. A message the following day however suggested that the object might be to jam rather than mimic British traffic. The same day, Oberst Aschenbrenner had advised Kesselring:
I have received your communication about WIM operations. Apparently a false impression has been created, ground WIM stations are at the moment only in a position to receive and are already working continuously for the WIM in Kunawi [sic]. the first two ground jamming transmitters will not arrive from the factory until next week. They will be brought over by air transport. Preparations are being made to operate in Western Crete and Derna.
Those two locations, a little under 300 km apart, lay at either end of the longest open sea section of Axis convoy routes to Benghazi and Tobruk. The latter was the more important because it was nearest to forward positions and had a rail link with the front. As the RAF’s Operational Research Section appreciated:
… shipping could creep down the Greek Coast, through the Corinth Canal, down the Aegean, and so direct from Crete to Tobruk. The only part of this journey which could be easily reached by our attacks was the last stretch and this was so short that it could be covered in one night and two short daylight periods; during the latter fighter protection could be provided. On the other hand this last section of the route was not unduly far from our forward bases in the Alexandria area …
As later experience would show, the expected transmitters had between them sufficient range to interfere with ASV. over the whole Crete–Libya gap.
On 11 September, Ju 52 KA+SB left Munich laden with additional gear and spares for WIM stations 5, 6, 7 and 9 as well as “domestic equipment of every kind for H[orch] Trupp El Daba”. Some of this material—requiring “the most careful handling”—would be unloaded in Maleme before the Junkers carried on to Derna and El Daba. The final instruction was that, “the setting up of the transmitters is to be done with all speed”, probably referring to the two Karl sets destined for WIM 7 at Derna. Next day saw an order passed to Sonderführer Mahlow, WIM 9 at Derna that Sonderführer Unger was to be sent to Crete-West to set-up a Nachtfalter installation there.
A partial intercept on 15 September referred to the Nachtfalter equipment of WIM 1 at Noto. On the morning of the 16th, Fl.Kps. X was told that He 111 CQ+TD would be leaving Berlin-Tempelhof, carrying the requested radar-monitoring supplies. Feldwebel Kaltofen (presumably travelling aboard the Heinkel) would be a radio/radar operator and Fliegeringenieur Herold would repair the monitoring sets. The latter, incidentally, was not permitted to go on night flights as he must remain available for work.
The next known operation by the Kommando came ton the 14th, one of the two aircraft involved taking off at 1545. On the 16/17th an He 111, in the air from 2110, jammed three frequencies from 2215–2250 but broke off with technical defects and landed at 0232. The British later inferred from information given by prisoners that this may have been a sortie flown by Obltn. Schwaighart in an He 111 fitted with the Protekt system (see below). He had escorted a convoy between Crete and Tobruk, jamming the ASV of approaching British aircraft and had seen their flares drop far away from the five Axis ships. A similar success was thought to have been achieved early on the 15th as well.
Covering the MV Nerucci on the 17/18th were two Heinkels: the first started at 1615 but its equipment failed and the second machine took off at 1902 hours. The next evening one He 111 took off at 1800 and the other 12 minutes later, to protect MV Foscolo. One these jammed four frequencies but the other had receiver problems and could not complete its task; both had landed by 0226 on the 19th. This airborne effort had been supplemented by the Nachtfalter (WIM stations) in Derna and Crete-West, “both to their full extent for the first time”, apparently thanks to the recent deliveries of equipment. Two jammers flew on the next night, one from 1800–0615, this exceptionally long endurance made possible by an intermediate landing. The second took off at 1815 but was back after 15 minutes due to engine trouble. During the 19th, the Kommando’s TM+KM flew from Heraklion to Kalamaki, GJ+JH making the same trip next day.
Repairs to an 800 W transmitter at Derna on the 19th were expected to affect the control of fighters two days hence, given that ZG 26’s 1 kW set was needed for other operations. One proposed workaround was to use equipment at the WIM station but that would leave it unable to fulfil its normal functions.
From 0015–0205 on 20 September, Beaufighter X7702, ‘K’ was on a sortie from Luqa, Malta and, as P/O Pat Bing of No. 89 Sqn. reported:
Echoes obtained twice at from 15,000’ to 12,000’ [4500–3650 m] but was lost in strong jamming from 4,000’ to 5000’ [1200–1500 m]. Echo was very good to start. Became weak first and was then jammed out … Suspect jamming may have been airborne as it didn’t become serious until about 4–5,000’ from E/A. The blip disappeared from jamming & apparently E/A increased speed and evaded violently. Suspect they have some indication of night fighter behind them.
Also on the 20th, the Air Ministry noted: “Malta reports Mark VII AI [a prototype centimetric set] inoperative at heights now used by enemy night bombers and that enemy rapidly follows changes of frequency on Mark IV gear”. Three days earlier Malta had told Air HQ Mediterranean that: “airborne jamming considered to be more effective than ground jamming which does not render our GCI completely unserviceable”.
No jamming was attempted by ground stations on the 21st but German monitors noted eight active ASV’s as well as establishing the existence of a radar station on Cyprus, two in Egypt and four in Palestine. The “take” two days later was five ASV aircraft operating by day and six ground radars. Warning was also passed that German radar operators should be alert to the possibility of British jamming and report any external sources of interference.
continued on next page …