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’ (one of the two “specials” equipped to home on jamming) 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 … Gain control made no difference … Tuning made difference only when frequency of transmitter was changed (with special mod.) but only for a brief period … 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”. These difficulties were apparently remedied locally and during September the Mk. VII installations in V8219 and X7840 were sucessfully tested by F/O Shipard and F/S Oxby up to 24,000 feet (7300 m).
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.
One of two He 111 detailed for ASV jamming on 22 September took off at 1615 and two more operated the next night, one taking off at 1649; they landed at 0030 and 0530 hours. These machines had been protecting the tanker Rondine, as was a lone Do 217 night fighter which had started at 2100 hours. El Daba meanwhile had been ordered to jam GCI radars in the Nile Delta for two hours from 1800. Early on the 23rd, the WIM-Zentrale had advised its sub-stations that a calibration flight would take place from 0600 hours with selected frequencies being jammed in succession:
That night, two He 111 operated on convoy protection, from 1640–0032 and 2029–0552, jamming three frequencies while for its part Crete-West was transmitting from 1855, jamming no fewer than eight wavelengths. During the day a WIM company informed a Ltn. Einwaller that “Feegenmann” (another officer?) had taken over WIM 2’s traffic and asked why that station had not so far reported to WIM 3. A “signals Junkers” (probably a Ju 52) was due in Benghazi on the 24th to work with existing aircraft reporting services, providing an R/T relay for the fighters based there, and on the following day Ju 52 NR+AE flew between Heraklion and Kalamaki. That morning, the Middle East Y-Service signalled the Air Ministry as follows: “Probable that P4 BA and DA ASV jammers (Query Wildschwein).” This particular hypothesis was mistaken since P4 was the unit code of Fl.Kps. X’s Führungskette (HQ flight). Also, WIM 8 reported that its western sections were being fenced round with barbed wire, work expected to take two or three days.
continued on next page …