Transcript from AIR 20/8448 Public Records Office, Kew

PROGRESS REPORT NO. 4 ON R.C.M. INVESTIGATIONS BY AIR COMMAND SOUTH EAST ASIA

Appendix "A" - Map showing enemy ground radar installations in A.C.S.E.A. area.

Foreword:

Part I of the following report deals in general terms with the results of recent investigations in the light of previous knowledge.

Part II includes a more detailed discussion fo the Flight investigations.

Part I

Introduction

2. The Report covers results obtained by Special Flight 159 Squadron between 16th Jan. and 26th feb. 1945. Previous results were included in Progress Reports Nos. 1 -3.

3. Total number of sorties flown 11

Abortive Sorties 1

Aircraft lost on operations 1

4. The loss of aircraft "W" flown by the Flight Commander on the night of 31Jan/1 Feb. left the Flight with one aircraft only. Investigation flights were continued but the results obtained lack the corroboration of an independent check. A replacement aircraft has been delivered and the task of installation of the special equipment is now in progress.

5. It is proposed that 1341 Flight shall operate from Digri in co-operation with Special Flight 159 Squadron as soon as the former has assembled. 1341 Flight will consist initially of six Halifax III aircraft equipped for investigation Japanese Radar and Radio transmissions. Task Investigation Order No. 1 to 1341 Flight refers. Detailed analysis of Flight Reports will in future be carried out by specialist officers at the Flight thus ensuring quicker dissemination of information concerning new interceptions.

6. An outstanding feature of recent investigations is the dearth of Jap. Radar signals. With a single search receiver in operation it takes some considerable time to cover the frequency spectrum. During which time a station may con on the air, fix the aircraft and go off again without being intercepted. It has also been suggested that certain radar stations function only when a number of aircraft are operating in their vicinity Several attempts have been made by single investigation aircraft to bring suspect radar stations on the air by lingering in their neighbourhood, but the stations have almost invariably remained inactive. If these tactics are being adopted, the chance of interception and fixing will be enhanced only when several aircraft of the Flight operate together.

Results Obtained

Bassein Area

Several flights have covered this area but no signals of local origin have been received. Radar must therefore remain "Suspected".

Rangoon Area

The 68 Mc Signal was heard on two flights but no conclusive D/Fs were taken owing to continual sweeping.

The 79 Mc. Radar was boxed to an area 3 miles by 1 mile running East and West with the centre in Rangoon itself.

There was no evidence of the suspected 100 Mc station in the Rangoon area.

Moulmein Area

No further 200 Mc or 70 Mc signals have been heard in this area but it cannot be assumed that the existence of either Radar has been disproved.

Bangkok Area

This area was covered on two sorties but no signals emanating from the immediate vicinity of Bangkok was found. From a point 100 miles South of Bangkok, in the Gulf of Siam a brief signal having the following approximate characteristics was intercepted.

R.F. 75 (?) Mc/s P.R.F. 1500 or higher

Mergui Area

Photographic proof of the existence of Radar on Mergui has been obtained. C.P.I.C. Detailed Interpretation Report No. U 27 refers. This radar is now classified "Definite". No signals have, however, been received from this area recently.

Port Blair Area

The known 98 Mc Radar has been heard on every occasion the investigating ircraft have been in the vicinity of Port Blair but it has frequently come on when the aircraft has been leaving the area, not when approaching. On run of D/F's cut on Mt. Harriet.

Penang and N. Sumatra

Special attention has been paid to the 100 Mc. Radar on Penang which has been boxed and D/F'd to a hill 2722 feet high at 100º 15 ' 10" E/ 05º 25 ' 50" N. Photographic reconnaissance is being requested.

The 76 Mc signal was again active and came from some distance West of Penang. Again several bearing cut in the Malacca Straits indicative of a shipborne installation.

The rare phenomenon of a secondary echo from this transmission was observed on one occasion for a period of 14 minutes.

Car Nicobar

A 195 Mc Mk.1 Model 2 Radar was carefully boxed and D/F'd on 26th. Feb. six bearings intersected at 92º 40'E/ 09º 11' 10" N. As this position does not correspond with that given in C.P.I.C. Interpretation Report No. U 24 for the site of the 100 Mc. Radar, a further reconnaissance is being requested.

Great Coco Island

There has been no evidence of any transmission from Gt. Coco Island Radar.

On the night of 28th Jan. when aircraft approached Penang for mining operations, the M/F beacon at Georgetown went off the air when the aircraft were 150 miles away. As their track lay over Great Coco Island it is possible that they were reported by aural interception.

Search was continued for signals with airborne characteristics but nothing suspicious was found.

On the last two flights a listening watch was kept for enemy R/T and W/T. Analysis of any interceptions is being done by A.T.I.S.

New Signals

The source of the following signals in not known:-

28.4 Mc/s 300 P.R.F. Intercepted near Puket. No bearings taken

27.5 " 260 " Intercepted over North Andamans. No bearings taken.

79.4 " 395 " Over sea midway between Rangoon and N. Sumatra. No bearings taken.

69.1 " 100 " Bay of Bengal. 100 Miles W. of Ramree.

75 (?) " 1500 (?) " Gulf of Siam e. of Mergui.

186 " 1120 " Over Elephant Point. D/F to Seawards.

220 " 525 " Over Port Blair. Has the characteristics of Mk. 2 Model 1 Modification 1 or 3 but may have been Type 291.

END OF PART I

Part 2

ANALYSIS OF AIRCRAFT LOGS BY FLIGHTS