[8.5] JAPANESE RADAR TECHNOLOGY AT WAR
* At the end of 1941, the Japanese began a wide-ranging offensive that swept through the colonial possessions of the British, Americans, and Dutch in the western Pacific, reaching as far southeast as the north coast of New Guinea to threaten Australia. Among the benefits of this spectacular wave of conquest was the fact that the Japanese obtained a number of British GL-type sets in Singapore, as well as a US SCR-268 set and a damaged US SCR-270 set on Corregidor.
The IJA put a modified version of the GL into production as the "IJA Tachi 3". It operated on a band around 3.75 meters (80 MHz), had a pulse width of one to two microseconds, a peak power of 50 kW, a PRF of 1,000 or 2,000 Hz, and a maximum range of about 40 kilometers (25 miles). About 150 were built by Sumitomo, with the type going into service in early 1944. The Tachi 3 set was the first Japanese set to incorporate Yagi antennas, which was a great irony, since such antennas were the invention of Hidetsugu Yagi, a Japanese electronics researcher of global stature. To add to the irony, Dr. Yagi had been involved in the development of the IJA Type A interference detector.
On their part, the IJN recognized the SCR-268 as a good piece of gear and put a derivative of it into production as the "IJN Mark IV Model 1". It operated in a band around 1.5 meters (200 MHz), had a pulse width of 3 microseconds, a peak power of 30 kW, a PRF of 2,000 Hz. and a maximum range of about 48 kilometers (30 miles). It was followed by the improved "IJN Mark IV Model 2", which had basically the same general specifications except that the PRF was reduced to 1,000 Hz. The Japanese built a few hundred of these radars in all.
The IJA also tried to build derivatives of the SCR-268 in the form of the "IJA Tachi 1", "IJA Tachi 2", and "IJA Tachi 4", all operating on the 1.5 meter (200 MHz) band used by the SCR-268, but these radars did not prove satisfactory and were only built in small numbers. Late in the war, the IJA did introduce a much more workable derivative of the Tachi 4, the "IJA Tachi 31", also operating at 1.5 meters (200 MHz), with 70 built.
* In the meantime, both the IJN and IJA fielded derivatives of their earlier fixed-site radars. The IJN Mark I Model 1 was followed in 1942 by about 300 of a lighter transportable 1.5 meter (200 MHz) version, the "IJN Mark I Model 2", and then in 1943 about 1,500 of an even lighter portable version, the 2 meter (150 MHz) "IJN Mark I Model 3".
As if in parallel lockstep, the IJA followed their Tachi 6 in 1943 with about 60 transportable 3 meter (100 MHz) "IJA Tachi 7" sets, and in 1944 followed that with about 400 portable "IJA Tachi 18" sets, operating in the same band.
Other than being lighter, these radars were no great advance over their predecessors, being roughly comparable to the British MRU. However, since the Japanese had developed their own magnetron, in fact well ahead of the Allies, they also developed their own 10 cm (3 GHz) microwave set for naval warfare. The "IJN Mark II Model 2" radar was introduced in 1942, and was well-received by naval crews as a great step ahead of the unsatisfactory longwave Mark II Model 1. About 400 were built and deployed on a range of vessels.
The Mark II Model 2 had a peak power of 2 kW, a pulse width of 2 to 10 microseconds, a PRF of 2,500 Hz, and a range of about 35 kilometers (22 miles) against a large naval surface target. It had separate cone-shaped transmit and receive antennas, giving it the odd appearance of giant toy binoculars. It did not have a PPI, no operational Japanese set ever did, which greatly limited its usefulness for naval operations.
The Japanese also developed a lightweight longwave set, the "IJN Mark II Model 4", operating at 1.5 meters (200 MHz), for use on small vessels and submarines. It is unclear if it saw much service.
* During the first months of the US war against Japan, the Americans were so overwhelmed that worrying about Japanese radar capabilities didn't even make the list. The issue didn't bob to the surface until the US Marines landed on Guadalcanal in the Solomon Islands on 7 August 1942. The landings were not heavily opposed -- a situation that gave a completely misleading impression of what to expect in the future -- and the Marines quickly captured an IJN Type I Model 1 radar. The catch came as a surprise, apparently less because anyone thought the Japanese didn't have radar than because few had given the matter much thought. The Japanese radar was dismantled and shipped stateside. NRL researchers found it crude, even in comparison with early American radars such as the SCR-270 and CXAM.
SIGINT receivers were quickly installed on submarines and aircraft to hunt for more Japanese radars. A Consolidated B-24 Liberator ferret that had been fitted with various SIGINT gear, including some lab breadboards, performed probes of the Japanese-held island of the Kiska in the Aleutians in March 1942, and discovered the signatures of two more IJN Type 1 Model 1 radars, which the SIGINT operator reported sounded exactly like the signature of the US SCR-270 longwave radar. Consolidated PBY Catalina flying boats were also configured as ferrets, and more Japanese radars were soon identified.
Submarine ferrets would prove as effective as their flying brethren, possibly more so because the enemy generally didn't know submarines were around and didn't turn off their emitters. However, no other types of Japanese radars were detected through most of 1943, though there were rumors and bogus "sightings" of other types, such as airborne radars that the Japanese simply didn't have at the time.
Better information began to trickle in towards the end of the year, and in February 1944, following the capture of Kwajalein island, the Americans found documents describing a number of Japanese radars, most interestingly the centimetric Mark II Model 2 shipboard radar. Further landings during the spring and summer revealed more data about Japanese radars, including some sets captured intact.
Nigdy na pewno nie doszli do takiego etapu jak USA/GB, gdzie pod koniec wojny radary na niszczycielach pozwalały na wykrycie peryskopu zanurzonego okrętu.
Zamieszczone przez mossin
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