Listening and Jamming (page 3)

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From the night of 5/6 July onward, traffic was picked up disclosing overnight maritime surveillance (Überwachungsflug in German messages) by radar-carrying Fw 200s of KG 40. It certainly made sense for the Germans to be watching Biscay by night as well as by day, for the safety of U-boats on passage as well as their own surface units. Among the aircraft whose signals were picked up was “D”, factory marking CE+IO (Fw 200 C-4, W.Nr. 0150). The 13th saw the Cheadle intercept station picking up on “unusual activity from the Bordeaux area”, some form of exercise involving a ship, a plotting station, an aircraft and its ground controller. Although the aircraft was off Royan at midday, the ship had still not sailed over three hours later.

On the night of the 15/16th, aircraft “A” was active west of La Rochelle after taking off at midnight but turned back inside the hour after reporting — in plain language, because it had no code book aboard — a defective “HTL” (Hohentwiel radar). A nine-hour sortie from 1945 on the 20th was attributed to III./KG 40 however. Shorter night flights with radar also took place, some attributed to exercises. In Britain this was noted as “the first direct evidence of ASV being fitted in Fw 200 aircraft in the Western area”. The unit concerned was thought to have been the 2. Staffel which had been withdrawn from operations at the end of May for, it was believed, re-equipment/retraining.

ZTPGU16691

Meanwhile, the Kriegsmarine was introducing new monitoring receivers but for the time being only prototypes were available, with just two sets expected during July. There was an “ASV Flight” by one aircraft on the night of 30/31 July, the machine being told in the early hours to land at Cognac rather than Bordeaux. When the first overnight operation by an He 111 was noted, on 31 July, it too was thought to involve Air-to-Surface-Vessel radar (times given are GMT + 2 hours):

ASVFlight

Meanwhile, the Kriegsmarine was introducing new monitoring receivers but for the time being only prototypes were available, with just two sets expected during July..

NOTE: There are reasons to doubt that the pencilled-in code belonged to an He 111. On 29 July, F8+AD reported probable damage to a 7,000 ton merchant vessel during an attack by ten Fw 200 on convoys SL 133 and MKS 18; the same machine called base about engine trouble at 0930 GMT and was expecting to land at 1230. Early in the morning of 31 July, it was reported as an Fw 200, in contact with Bordeaux and told to land at Cognac. A British Intelligence report summing up the night’s operations read: “The aircraft was stated in a naval circular to be an He 111, and was probably F8+AD”, with a pencil line through those last four words.

Finally, Chris Goss has published photographic evidence that in August 1943 F8+AD was Fw 200 C-6, W.Nr. 0218.

At the end of July, the submarines were directed to make only sparing use of "Metox" for fear that Allied aircraft were homing on its emissions. An inspired piece of misinformation from a prisoner “confirmed” this suspicion and by 12 August boats had been told to stop using it altogether. However U-161, the first with the new “Hagenuk” warning receiver, had sailed four days earlier and the device had worked perfectly all the way across Biscay:

Hagenuk

NOTE: The new device was variously known as »Hagenuk-Gerät« (after its manufacturer, Hanseatische Apparatenbau Gesellschaft, Neufeldt und Kuhnke GmbH), FuMB-10 and “Wanze.” This last was both a contraction of Wellenanzeiger (wave indicator) and the German word for “bedbug.” On 8 September BdU recorded that, “the number of planes operating has increased [but] hardly a submarine has been spotted or attacked since Wanze gear was installed in place of Metox gear. Thus, the anti-submarine defence situation has completely changed”. Five days later he signalled to his command, “Events in Biscay have shown that in the field of radar detection the situation has changed materially in your favour”.

Both sets were temperamental yet considered vital to the continuation of a cruise. On 18 July, her second day out from Brest, U-383 signalled that she was returning because “D/F gear is leaking badly and is soaked. Hydrophone gear and Metox out of order”. On 2 August U-448 turned back for St. Nazaire since “Metox defective, cannot repair owing to lack of spare resistances, Query: provision of spare Metox.” The 28th of August saw U-378 leave La Pallice only to abort her cruise just before midnight: “Hagenuk not working. Transformer mains unit burnt through.” The following day, after sailing from the same port, U-341 reported:

Hagenuk defective. Line base (Zeilenbasis). Long anode voltage was 480 volts instead of 320 volts. High ohmic resistance in the main unit burnt out. After exchange voltage fell to about 100 volts. Making good according to book without success. Have begun return passage with escort.

continued on next page …

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