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Pacific Thunder
Join Date: Apr 2004
Location: Yellow Sea
Posts: 1,896
Downloads: 236
Uploads: 14
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Quote:
Originally Posted by Cap'n Dud
Realizing this original post is from 2008, just FYI that in 2017 the link is
no longer valid. No point going to it.
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I think this is it:
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Quote by krazyfrenchman
08-26-2007
Quote:
Historical RADAR depiction in WWII versus depiction in SH4 ...
Finally, this is the oft-delayed RADAR coverage complementing the research on U.S. submarines that tambor198 posted a while back. In fact, this project was brought underway due to important questions VikingGrandad and I surmised to answer; they were to shed light on discrepancies we thought needed correction. We then suggested tambor198 to cover through service history writings and picture support each and every class of U.S. submarines found in the game. Over the general course of this discussion, Radar types and when they were installed on boats would be covered; and I will go even further in explaining Japanese radar use and their ASW doctrine as well in order to grasp the erroneous characterization Japanese AI and their weapon specifications were granted into the game versus historical accounts. For information's sake, here are the links to tambor198's threads:
Sub Comparisons......SHIV vs History (Balao Class)
Sub Comparisons......SHIV vs History (Gato Class)
There are three radar types (and their subsequent field-modifications and upgraded variants), appropriately scaled down from their ship counterpart to fit in a cramped and crowded conning tower, which are of interest to us: SD radar, SJ radar and ST radar. All other types became operational only after Q1 of 1945 and thus do not concern the game in any significant way.
OVERVIEW SD: A range-only unit in a retractable mast with a "T" top, it served as early warning against attacking aircraft. SJ: A centimetric (10cm) surface search radar based on the British-provided magnetron. The SJ-1 was introduced in 1944 with a plan position indicator (a.k.a. PPI), which gave a familiar sweeping picture of the area surrounding the submarine. ST: A microwave surface search radar with its antenna in the periscope. It used the SJ installation to give range, but the bearing information was a function of the periscope's pointing. [Introduced late in 1944, presumably mid-October or beginning of November.]
Descriptive Brief
The SD radar was different depending on which type of boat (prior to the Tambor-class) it was installed, sometimes having its own mast aft of the conning tower with its usual "T" shape antenna or whip antenna on top or the observation periscope having a whip antenna mounted around the top in such way that it would not annoy the observer. The SD units were ordered into production in Aug. 1941.
Of note, from 1943 on, U.S. skippers suspected that Japanese warships could detect omnidirectional emissions originating from the SD radar array which was verified after the war. Japanese escorts started to be equipped from 1942 and most by 1944 with a shipboard radar detector, furthermore a directional one. First priority was going to ships within IJN Carrier Task Forces. Albeit, interestingly, the first few ASW aircraft were not equipped with these instruments until Dec. 1944 while accounts stating such aircraft were homing in on submarines could not be thoroughly confirmed.
The first SD would be available for installation in Oct. 1941, production of 60-135 following at 7 per week. While the first SJ units were expected for Jan. 1942, it was decided because of the threat aircraft presented that all submarines were to be fitted with SD, but only modern ones with SJ. By 1 February 1942, on Cuttlefish, Plunger, Pollack, Pompano, Tuna, Gar, Grampus, Grayback, and Drum, had operational SD radar. Performance against low-flying aircraft was disappointing due to the radar's low frequency (which brought its lowest lobe well up from the sea surface). The only indicator was an A-scope with one range scale (30nm). Typical ranges were 20nm for a bombers and 14nm for a fighter at 10,000ft, and 5nm for a destroyer (note to self: good to know).
Sixty SD were made; they were field-modified to SD-a by the summer of 1942. This version had a new horizontally --rather than vertically-- polarized antenna. SD-1 (20 made) was a version for submarines with fixed rather than retractable antenna masts. Later, 60 SD-2 (virtually identical to SD-a) were ordered and the first was installed in the fall of 1942. Meanwhile SD-3 (125 sets made) were small-boat sets converted back to submarines standards and started being installed Q2 of 1943. Finally SD-4 (104 delivered between July 1943-July 1944) was similar to SD-2 but with 15nm and 60nm range scales. They were installed from the moment of delivery. SD-5 which was slated to be replaced by SV radar types were scarcely equipped on boats and does not deserve much attention.
* SD: basic SD radar unit build from the original blueprint. Originally with an antenna on the vertical.
* SD-a: same as basic SD but vertical whip antenna field-modified to an horizontal plane.
* SD-1: Fixed antenna mast instead of retractable.
* SD-2: Own manufactured set with horizontal whip antenna based on the the SD-a field modification.
* SD-3: Small-boat SD radar sets converted back to submarine sets. [Probably redesigned as fixed antenna masts]
* SD-4: Comparable yet upgraded SD-2 sets with 15nm and 60nm range scales.
The SJ radar was a revolutionary type of radar. It dramatically shifted from day to night submarine attacks. Because Japanese surface radars were ineffective, a U.S. submarine could operate freely on the surface at night, even in the face of escorts (few of which had radar before Sept. 1944). Using SJ, she could confidently attack at night after spending the day trailing her target at or just beyond the horizon. In 1942, when only a few submarines had SJs, 30% of attacks were conducted at night. In 1944, it was 57%.
The first unit was installed in June 1942 but was field-modified to SJ-a not long after and by the end of that summer all were re-labelled as SJ-a. It now had a PPI, and its training mechanism was altered to turn at variable speed (10 RPM down to 1/20 RPM or less) or even manually and in both clock and counterclockwise directions. Range and bearing data could be fed directly into the TDC. Initially, the limited height of the antenna (33ft) gave a typical maximum range of only 5nm, but in the summer of 1943, power was increased by 50% (by the use of a 50kW transmitter instead of the SJ's original 30kW) and a new slotted parabolic antenna was fitted and this modification was designated as SJ-1. Over the course of 1943-1944 most SJ-a units were improved to SJ-1 standards. This SJ-1 could detect a BB at 12nm, a surfaced submarine at 5nm and a bomber (alt. of 500ft) at 5nm. Most WWI submarine designs could not have SJ radar installed as it would not fit easily.
+ SJ: manually-trained mechanism with only an A-Scope with main and precision sweeps (10nm and 30nm range scales).
+ SJ-a: field-modified from SJ with a plan-position indicator (PPI) and alongside improvements an automatic scanning function. Training mechanism have more functions to set on variable speeds and collected data can be directly fed to the TDC.
+ SJ-1: change of transmitter from one of 30kW to one of 50kW giving overall 50% more power to the microwave signal while also displaying a new slotted parabolic antenna on its mast generally just abaft the periscope "mountings", or in naval terms the periscope shears.
The ST radar, the other new X band radar (3cm rather than 10cm like wavelengths like SJ ones), was a range-only radar (although just in theory) for the head of the night periscope (i.e. obs. periscope). Developed in 1943-1944 and coordinated with the development of the Type 4 periscope (slated to replace the Type 3 night periscope), it became operational late in 1944. The Type 4 periscope had a "fatter" head (to gather more light: 3.75-in diameter) and was shorter than the other instruments (to lose less light in its tube). Like the earlier periscopes, it elevated between minus 10 degrees and plus 45 degrees. The first production Type 4 (w/ ST incorporated) was shipped 9 July 1944.
ST radar used a radar transmitter related to that of the contemporary Mk 13 on board battleships. As said earlier, theoretically it was a range-only radar, but in fact its 30 degree beam could measure a bearing to within an accuracy of 3 degrees. ST radar initially used the SJ A-Scope. Between Nov. 1944 and by 1 March 1945, 95 Type 4 periscopes had been installed. ST-a and ST-1 would become available only from May 1945 and does not transcend on SH4.
- ST: an array embedded within a Type 4 periscope (the strip under the "window" of the observation periscope), it used the SJ A-Scope to provide range and could pinpoint, once the periscope faced a certain direction, the bearing of a target (± 3 degrees).
Japanese Anti-Submarine Warfare was quite possibly the weakest element when one looks in retrospect to war in the Pacific theater. The IJN neglected ASW before the war with the U.S.A erupted and it severely hampered Japanese submarines operations as a result. This doctrine, or lack of doctrine thereof, led to almost no understanding of thermal layers or water stratification's. Hence, that it be on IJN destroyers or submarines, few were the captains who had an idea of sound detection beyond the thermal layer. The Japanese used both active and passive (often sonic) sonar. A postwar U.S. report considered their listening gear (at the outbreak of war) "every bit as good as ours" but their active sonar no more than fair. However, "early in the war they repeatedly demonstrated facility in locating a submerged submarine by using sonar and in this respect their ASW craft appeared to be on a par with ours." Hydrophones could detect a U.S. submarine at about 5,000 meters (2.7nm or 16,500ft) while running at about 5kt; active sonar had a maximum range of about 3,000 meters for a ship running at 12kt.
Later, once better U.S. submarines would become operational, they would dive well below that of effective sound detection for Japanese instruments, mainly due to "slipping beneath the thermal layer". In the same line of thought, Japanese destroyer depth charges did not explode deep enough to collect success, until a leak from a press conference influenced their set depth, which they changed presumably between 250ft and 300ft; still to shallow for the specifications of many types of U.S. submarines. Escorts tactics also were problematic. Instead of focusing on pursuing the attacker, especially at night with their lack of radar early in the war, they would start getting confused if the cargo ships within the convoy were hit or [torpedo] explosions nearby were heard. The evading submarine would have an easier time escaping if his attack was successful in the end.
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Now, we can discuss. We should try to cover how things work in the game and what is found amiss when we look at the radar upgrades that we get in-between missions and the way they work or are displayed in-game once installed. The pink text highlights the types of radars that should be available as upgrades in the game. Also, are the dates historically sound when we get them in SH4?? That another question that needs to be answered here.
I hope that we will get answers for all this!
Thanks for reading!
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03-06-08, 09:52 PM
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