After interrogating the pilot of U5+HH, the RAF learned that Kettenhund did not require a special aircraft and could be fitted in a bomber without reducing its normal warload, but was inaccessible in flight. It was controlled by the Bordfunker via a simple on/off switch, the frequency to be jammed being set before take-off.
A German position paper of 8 December 1944 described Kettenhund as an airborne jamming transmitter for use against British and American ground-based and aircraft radars including ASV and night fighter AI. Its frequency range was 170–220 mHz. Only provisional test results were to hand and the set had been used operationally over England but not often to judge its effectiveness.
Late in February 1944, the French-based II./Luftnachrichten Funkhorch-Regiment West reported to a visting delegation from the RLM on comparative trials of two W/T jammers, Starnberg II and Nervtöter (“annoyance”). The latter had been judged a failure with experienced Telefunken engineers unable to keep it set to the required frequency, even when they knew in advance which one they were to jam. Nervtöter needed constant attention while in the air and sufficiently accurate tuning was impossible. Starnberg by contrast was producing good jamming effects over a range of 30–50 km while flying at 2000 m and was effective out to 40 km when at an altitude of 150 m. Some 25 Starnberg II sets had been produced by 21 February; now they only awaited tuning-in, and two engineers from Köthen were requested for this task. A production set was currently being installed in a Ju 188 by the Villacoublay workshops and should be ready by the end of the month. Given the planned operating altitude of 7000 m, the antennae were being installed in the wings, pointing downward but could easily be changed to radiate upward. The jammer had an output power of 30–50 Watts. Three, aircraft, each with two transmitters, their frequencies set narrowly apart, could cover the 100–124 MHz waveband and effectiveness would be increased if there was multiple coverage of the band. It was envisaged that machines carrying jammers would be deployed in the van, middle and rear of the bomber stream. Further conversions could be carried out using about 50 French-built “replica” Starnberg I and the necessary parts for the installation would be indented for shortly from the RLM’s Chief of Signals. If the transmitters were required in greater numbers, orders must be placed as quickly as possible but none of the components was in short supply. The plan was that II./KG 6 should receive the first Starnberg while II./KG 2 would get Kettenhund.
At the end of February, IX. Fliegerkorps had reported good results with 80 cm Düppel strips in its most recent raids on London. Radio monitoring had revealed confusion within the British reporting organisation, night fighters had chased one another on several occasions and searchlight beams had been lowered. Anti-aircraft fire however had been well-aimed. From 50 km off the enemy coast each heavy bomber’s Bordmechaniker dispensed 1,000 Düppel strips every 30 seconds, intensify to 1,000 strips every 5 seconds over the target. A heavy bomber could carry two packets of Düppel. (In this context, "heavy bomber" probably covers all except the Me 410s and Fw 190s operating in support of the main force). Oberleutnants Albert Frankford and Peter Berresheim of the IX. Fl.Kps. Signals Staff told their visitors that on raids their aircraft flew in “the greatest possible concentration”: bomber stream 80 km in length by 10 km wide, duration of attack 15 minutes. This seems highly optimistic in view of the often haphazard, even shambolic, incursions reported by the RAF during the “Baby Blitz”.
The National Archives, Kew, London:
AIR14/2898: Enemy Radar Jammers “Airborne” (May 1944)
AIR20/8964: Enemy Countermeasures to RDF, Jamming Reports (J. Watch) Western Europe: Sep 43–July 44
AIR40/2417: Interrogation of German and Italian Prisoners of War, Vol. 22, Reports 153–322 (1 April–30 June 1944)
AVIA6/14410: Royal Aircraft Establishment Farnborough, Technical Note No. Rad. 170, “Anti-Jamming Measures for A.S.V. Mark II” (November 1943)
Canadian Department of National Defence:
Directorate of History and Heritage, Kardex system (Reel T-2422): http://heritage.canadiana.ca/view/oocihm.lac_reel_t2422/1?r=0&s=1
USAF Historical Research Agency, Maxwell AFB, AL:
Chef NVW 4. Abt. (III): Aktenvermerk über die Dientstreise des Gruppenleiters III in den Bereich der Luftflotte 3 vom. 18.2. – 28.2.44 (dated 11 March 1944)
NOTE: The main source here contains a preliminary report on a captured transmitter. It concludes with the words, "The equipment has been sent for laboratory examination to R.A.E. and a complete report will be issued". To my frustration, that National Archives file is "wanting".