Transcript from AIR 20/8446 Public Records Office, Kew

PROGRESS REPORT NO. 3 ON R.C.M. INVESTIGATIONS BY AIR COMMAND, SOUTH EAST ASIA

FOREWORD.

This report is divided into two parts, namely, Part I which describes in general non-technical language the results achieved and the difficulties encountered, and Part II which is intended for more detailed study as required by specialist staffs.

PART I

INTRODUCTION

2. This report describes results obtained by Special Flight 159 Squadron between November 4th 1944 and January 16th 1945. Results previously obtained were included in Progress Reports Number 1 and Number 2.

3. The loss of one Liberator on the night Nov. 10/11th necessitated considerable effort on the part of the ground personnel of the Flight in fitting out a replacement aircraft. As a result of the co-operation of 20th Bomber Command, S.C.R. 587 equipment and a rotatable D/F aerial system were fitted and good results have been obtained without the aircraft being forced to enter heavily defended areas in order to "box" signals. All frequencies between 40 and 3000 megacycles can be covered. Tests on a British ground radar installation showed however that varying degrees of error similar to quadrantal error may be introduced on certain bearings. The new aircraft commenced operations on December 16th, 1944.

4. During December, 1944, a successful application was made to increase the establishment of Special Flight by one additional Liberator and appropriate aircrew and servicing personnel.

5. To prepare for possible future countermeasures, orders were given to Special Flight to prototype the fitting of "TINSEL" in a Liberator aircraft.

6. Arrangements were made for Special Flight, wireless operators to receive instruction to enable them to recognize Japanese W/T and R/T.

7. It is hoped to produce these reports at more frequent intervals but as yet the R.C.M. personnel who were expected, have not arrived.

RESULTS OBTAINED

8. Based at Digri the Flight has continued to operate according to the requirements laid down in Task Investigation Order No. 3, the main details of which were included in Progress Report NO. 2. In the course of these investigations new cover of the Andaman Islands has been obtained but data is as yet too scanty to determine whether enemy radar in the Islands is operational at a site other than Mount Harriett.

9. For the first time the existence in this theatre of an enemy 200 megacycle mobile radar installation was definitely proved. Close co-operation between the Special Flight and 159 Squadron resulted in the detection, photographing and bombing of a mobile radar located on the North West tip of Great Coco Island. Although no damage is visible on photographs it is of interest to note that no signals from this installation have been received since the site was bombed on December 17th, 1944. This installation is advantageously site to fill in the gap in radar cover afforded by stations sited in the Andamans and on the mainland of Southern Burma

10. Undoubtedly the most difficult task confronting the Flight has been that of pin pointing the sources of the 68 and 79 megacycle signals received in the Rangoon area. In view of the important part played by Rangoon in the defence of Burma much effort has been devoted to this task without, however, obtaining completely satisfactory results. Similar difficulty has been reported by 20th Bomber Command. Signals on the same frequency band which were detected in the area of Northern Sumatra have proved equally difficult to D/F.

11. Acting on information received from other theatres, search is now regularly made for Japanese A.I. signals, results so far have been negative.

12. In general, sorties undertaken during the period under review have largely confirmed results previously obtained with the exception of the probable radars at Akyab and Moulmein. In the light of this report the status of enemy radars in this theatre must be re-assessed accordingly In drawing up the revised assessment it has been decided to adopt the following standard categories: -

SUSPECTED One or more intercepts of random signals have been intercepted giving limited information but no confirmed position.

PROBABLE signals have been received giving definite characteristics and D/F allowing the position to be estimated.

HIGHLY PROBABLE Two or more independent reports boxing a station to a small area, or three or more intercepts on the same receiver and D/F bearings giving a cocked hat of reasonable dimensions.

DEFINITE Probable or highly probably confirmed by sightings, photographic cover or by other intelligence.

NOTE:- Stations may however be down graded should a large number of flights carried out over a reasonable period of time fail to corroborate results obtained during previous flights.

13. The Japanese continue to display their customary reluctance to operate their radar stations unless operational aircraft are also in the area. Flights undertaken during bad flying conditions have shown that watch is by no means always continuous.

RANGOON AREA.

14. No conclusive information has been forthcoming regarding the sites of the enemy radar transmitters on 69 and 79 megacycles. This are is heavily defended by A.A. and results obtained using the new D/F system have so far been conflicting. Investigations in this area are proceeding. The two stations on 69 and 79 megacycles are classified as "Highly Probable".

15. Intermittent signals have also been received on the 100 megacycle band and the existence of such a station in the Rangoon area is rated as "Suspected".

MOULMEIN AREA.

16. Despite frequent flights in this area no confirmation has been received of the signals previously received. In view of this the existence of the 200 megacycle and the 70 megacycle type enemy radars is down graded to "Probable".

BASSEIN AREA.

17. No new intercepts have been logged in this area, the 100 megacycle and 70 megacycle type enemy radars are reclassified as "Suspected".

BANGKOK AREA.

18. No signals have been received which would appear to have emanated from this area, although flights have been flown in an attempt to corroborate reports from other formations.

MEIKTILA AREA.

19. No signals have been received in this area.

PENANG AREA.

20. Flight No. 18 re-affirmed results previously obtained which indicated a "highly Probable" Mark I Model station sited within a small area in the North East Section of the Island. (Mid point at position 05º 26'N, 100º 17 1/2'E.) this station transmits a powerful signal from which it is assumed that Modification 2 has been incorporated. 70 megacycle signals have not been detected in this area during the period under review, but it is considered that the existence of such a station in the Penang Island area is "Probable".

MERGUI

21. Particularly as a result of Flights Nos. 3 and 4 the Mark 1 Model 2 radar installation is rated as "Highly Probable". Exceptionally accurate flying permitted a new estimate to be made of the position of the transmitter which is now calculated to be at 98º 40 1/2'E, 12º 27 1/2'N. I.e., on the high ground 3 miles E.N.E. of Mergui airfield. A photographic reconnaissance sortie to cover this point has been requested.

AKYAB AREA.

22. No radar ground stations were captured following the allied occupation of this area.

ANDAMANS.

23. Flights Nos. 9 and 10 indicated the possibility of a 100 megacycle radar station in the Aberdeen area which is only approximately 4 miles from the known site at Mount Harriett. This is considered to be an unlikely possibility which requires further investigation.

24. At least on 100 megacycle station at Mount Harriett continues in operation.

NORTHERN SUMATRA.

25. Signals on 73 and 78 megacycles which were undoubtedly of enemy origin were received over a number of hours when the aircraft was in this area during flight No. 18. Bearings were however most inconsistent and in view of the impossibility of indicating the area from which these transmission emanated, the stations can only be classified as "Suspected". Investigations will be continued.

GREAT COCO ISLAND.

26. Good photographs which were taken after signals had been boxed by the blight to the island, clearly reveal an enemy camouflaged mobile radar installation. The existence of this installation is rated as "Definite", but it is not known whether the station is now operational again. Two other structures are visible near this installation, these structures are uncamouflaged and it is probable that they are dummies. They do not conform to any known type of enemy radar station.

CLASSIFICATION OF ENEMY RADAR INSTALLATIONS IN ACSEA AREA.

27. The following summary is based entirely on results obtained by Special Flight 159 Squadron and on photographic evidence. As far as possible reports of possible enemy stations received from other source are always investigated.

(i) 100 Megacycle Radar

Definite (a) Mount Harriett (Andamans). Dual installations.

(b) Sabang

(c) Car Nicobar (Note: signals on 200 mcs. band have also been received).

Highly Probable (a) Penang

Suspected (a) Bassein area.

(b) Rangoon area

(ii) 200 Megacycle Radar

Definite (a) Great Coco Island

Highly Probable (a) Mergui

Probable (a) Moulmein

(iii) 70 Megacycle Radar

Highly Probable (a) Rangoon area. Two installations.

Probable (a) Moulmein

(b) Penang

Suspected (a) Northern Sumatra area. Two installations.

(b) Bassein area.

Sigs/1106/R.C.M.

12th February, 1945

PART II

ANALYSIS OF AIRCRAFT LOGS BY FLIGHTS