British Type 284 gunnery radar

Guns, torpedoes, mines, bombs, missiles, ammunition, fire control, radars, and electronic warfare.
User avatar
Dave Saxton
Supporter
Posts: 2926
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

British Type 284 gunnery radar

Post by Dave Saxton » Tue Apr 30, 2013 9:15 pm

The Royal Navy divorced itself from the RAF and the Army’s radar research and development programs from the beginning. The RN insisted on running its own secret program. At the end of 1935 the Admiralty outlined that the program would consist of experiments on 4 meters wave length (Type 79X) for air warning, 1.5 meters for ASV (Air to Surface Vessel), and 60cm for flak ranging. It is worth noting that no thought was given for what would be the far more important tasks of surface search or heavy artillery gun-laying at that time.

Up through mid 1938 the programs made little progress. At that point the Admiralty essentially fired the scientists conducting the research and put the program under the direction of a career naval officer. That officer was Capt. A J Murray. Murray appointed self taught engineer J F Coales to lead the 50cm program. (The 60cm program had changed to 50cm when Coales had earlier suggested they use a new transmitting triode designed to operate on 51cm already developed for the Army’s Flak directing radar program). Rather than flesh out the details in house, Coales and his team instead developed a general design and turned over the execution of those ideas over to private enterprise.

By mid 1939 a prototype flak ranging radar was made ready for initial testing aboard ship (HMS Sardonyx). The prototype was designated Type 282 and it consisted of a single yagi aerial in front of a of ½ cylinder reflector. The performance was not impressive. The bearing resolution was 37 degrees and the maximal range to aircraft was 4.5 km. At this point there still was no thought of developing the prototype into firecontrol radar for long range naval artillery.

This changed following the Battle of River Plate in Dec 1939. Reports were that AGS main battery shooting was much better than expected and photos of the scuttled wreck indicated the possible presence of a radar antenna mounted to the foretop range finder. A radar expert from the RAF was sent to Montevideo in Feb 1940 and his report sent shock waves through the Admiralty. It was indeed radar operating on a wave length of 57cm. This report was followed by knowledge that the Gneisenau had sought to disengage from the Renown on April 9th after damage to its foretop had disabled a radar apparatus.

By summer 1940, Coales and his team had been asked to also develop versions of the 50cm 282 set which could be used to provide supplemental ranging for heavy artillery (effective to 10 miles to destroyers) and for heavy flak. Coales used the existing experimental Type 282 electronics and rigged up a large antenna array consisting of a ½ cylinder metal reflector 21 feet wide with ½ wave dipoles arrayed inside of it. This type of antenna was given the nick name: “The Pig Trough.” This provisional set was mounted high up on Southsea Castle. The results were encouraging and in a Staff Meeting in June it was recommended by Commander Roskill that main battery ranging radar be developed which mounted the pig trough to the main firecontrol director. The first prototype (designated Type 284) was to be installed on King George V when it completed in Dec 1940.

Meanwhile another prototype using parts of the 282 was being set up on the battleship Nelson also during June 1940. This prototype featured a pig trough only 10 feet wide, installed upon the main fire control director some 30 meters above the surface of the sea. Despite the small antenna, test results were spectacular. Merchantmen we tracked to 33km and a destroyer to 22km. It was only discovered later that these results were the result of abnormal propagation. When the KGV was finally completed and the large antenna set installed on it tested, the results were as follows:

12,000 yards to a destroyer
20,000 yards to a cruiser

When Suffolk tracked Bismarck Type 284 was effective to 26,000 yards to the battleship.

These early Type 284 installations were all very much provisional prototype sets. Production would not begin until 1942 with about one 50cm set installed per week. The early 282 prototypes used the NT90 Micropup transmitting triode producing 5kw average output. The prototype 282 was the only naval 50cm prototype to use the NT90. The 284 was to use the new and improved NT99 Micropup triode. The NT99 was not certified for production by lab tests until April 1941 with production beginning in June 1941. These triodes had to be hand made with a production rate of about 8 per week. Since the Army’s gunlaying sets also used the NT99, spares were always in short supply. (This lead to the superseding of Type 285’s still in service during the 1950s with American Mk35 radars. Only about 10 sets total of Type 275 were ever built.)
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

User avatar
Dave Saxton
Supporter
Posts: 2926
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: British Type 284 gunnery radar

Post by Dave Saxton » Tue Apr 30, 2013 9:24 pm

Type 284M

Although the radar had proved its worth, pressed into surface search roles, during the Bismarck chase, it was considered deficient in terms of range performance and accuracy performance. Improvements were ordered to be made before production began in early 1942. Among the deficiencies were:

*Inadequate detection range
*Poor resolution for range and bearing.
*Poor bearing accuracy
*Poor range accuracy.

To address the bearing accuracy issue beam switching would be employed. The type of beam switching differed from the most common type of beam switching of switching two separate beams, but can better be described as beam steering. A single beam's aim was switched via a Geneva mechanism so that right and left sides of the beam alternately painted the target. The trace would flicker on the indicator if the return amplitudes from each beam position were unequal. If the return amplitudes were equal it would not flicker and the antenna was aimed directly at the target. The bearing accuracy was very impressive, being within 5 arc minutes at short ranges.

Despite complaints about the bearing resolution, the bearing resolution was actually quite good; being 3 degrees using max signal and 4.5 degrees during beam switching. By way of comparison the late war USN MK8 had a bearing resolution of 2 degrees, while the contemporary USN Mk3 had a bearing resolution of 15* while beam switching.

Resolution for range was improved from 300 meters to 150 meters by reducing the pulse width from 2 micro seconds to 1 microsecond.

Detection range was improved by both converting the 21 foot pig trough to common mode operation and by increasing power from 15kw average output to 60kw average output.# The range to a battleship was now 29,000 yards.

Range accuracy could not be improved at that time (the Precision Ranging Panel for the 50cm sets was not available until mid 1943). The range accuracy was 240 yards taken directly off the A-scope using the wire pointer which automatically transmitted ranges to the transmitting station. The radar operator could use a paper range scale template more accurately and then phone in the more accurate range to the transmitter station, however. The accuracy using this method was about 120 yards. However, as Derek Howse points out the accuracy of the optics aloft on the RN capital ships was +/- 1000 yards, so Type 284 was much more accurate than the optics alone.

In the meantime it was recommended that the new 10cm surface search sets be used to supplement the ranges taken by Type 284 and to assist in splash spotting. This practice was banned following the Battle of Barents Sea.

During 1943, the Precision Ranging Panel was finally made available. How this worked was that the time base was broken up into “range gates” of 1000 yards each. The range accuracy within each gate was typically 25 yards.

Also during 1943 an additional indicator with a long after glow was supplied to the transmitter station below decks. This was to allow the personal there to better correct MPI errors for range.

The final innovation planned for the 50cm radars were a new Micropup transmitting triode with 200kw peak output and about 120kw average radiated output. This new vacuum tube was never used, as the 50cm radars were slated to be replaced by new centimetric sets by 1947.

# This stat is taken from ADM CB4497. Many secondary sources list peak power of 125kw. One must be careful when using British peak output level numbers. The British used gas tube pulser to create the pulse and these created a tear dropped shaped pulse-viewed graphically. Therefore the average power of the pulse was a better indicator of the pulse power when used in comparison to other output stats. Typically the average power per pulse radiated was about 50% that of the peak power right at the tube’s output.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

User avatar
Dave Saxton
Supporter
Posts: 2926
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: British Type 284 gunnery radar

Post by Dave Saxton » Tue Apr 30, 2013 9:31 pm

The British 50cm sets used relatively high band width. The use of high bandwidth was so that a pulse with a good form or a relatively flat leading edge to the pulse could be created by the high voltage gas tube pulser. (The design called for a high voltage pulse to be delivered to the anodes of the transmitting vacuum tubes) However, the high band width meant that more noise was let into the receiver resulting in a relatively poor signal to noise ratio. Moreover, the signal to noise ratio required for detection is a function of matching bandwidth to the pulse width. The bandwidth should be the inverse of the pulse width. For example, if the pulse width is 2 micro seconds then the bandwidth of the circuitry should be ½ 1000 kHz. The British bandwidth was 4meg so there was a huge mismatch and the signal to noise ratio had to be large to detect targets. The signal to noise ratio is what results in a radar’s ability to detect small targets such as submarine periscopes or small shell splashes. Therefore, the British 50cm radars required relatively high transmitter power.

Besides higher power there are other ways to address this problem. One is to use shorter wave lengths. All other factors remaining the same a shorter wave length will increase the power of the return signal. But all things don’t remain the same. Vacuum tubes in the radar receiver becoming increasingly noisier as the operating wave length decreases. It begins to become a problem at about 75cm and reaches intolerable levels at about 33cm. Thus the Germans addressed this issue in Seetakt by increasing the wavelength to 80cm, bringing the wavelength out of the problematic area, which improved the signal to noised ratio using specially selected receiving pentodes from Philips of The Netherlands. The British lost access to Dutch tubes in the spring of 1940 and the American acorn tubes were also in short supply.

In the British 50cm radars, they addressed this issue by using unique grid grounded triodes which reduced noise to tolerable levels when operating at 50cm. Along with relatively high transmitter power the grid grounded triodes made operation at 50cm viable.

Another issue resultant from the use of anode modulation via high voltage pulser was a long warm up time. Not only did the transmitter tubes, with only very short voltage spikes delivered to their anodes, require a long time to reach a temp where electrons would start flowing, but the gas tube pulser itself required a prolonged period before it would begin to deliver a high voltage pulse. Warm up times could be as long as 45 minutes. Nor could they leave the radar switched on all the time because the gas tube pulser had a finite service life. For this reason Type 274 would use spark gap modulators
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

dunmunro
Senior Member
Posts: 3376
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British Type 284 gunnery radar

Post by dunmunro » Wed May 01, 2013 12:13 am

Dave, that's an interesting summary of RN radar and type 284 development, however, I think you've overlooked a few items:
3 Early radar development work
In August 1935, the Controller decided that the Experimental
Department, HM Signal School should start as
soon as possible to develop apparatus to detect and locate
aircraft by radio methods. A representative from Signal
School went to Orfordness for six weeks and then at a
meeting held at the Admiralty the requirements given in
Table 1 were laid down:
Table 1 : Requirements for radar laid down by the Admiralty
Aircraft:
Warning of approach 60 mile (96 km)
Precise location 10 mile (16 km)
Ships:
Warning of approach 10 mile (16km)
Precise location 5 mile (8 km)


On 30th September 1935 a letter was received from the
Board of Admiralty giving approval for the work to
proceed.
Development of radar for the Royal Navy
1935-44
J.D.S. Rawlinson, C.B.E., B.Sc.(Eng.), C.Eng., F.I.E.E.
The Admiralty was working on aircraft and surface gunnery prior to Sept 1939.

Pout states that 282/3/4/5 PRPs were in service use by spring-summer 1942.

Obviously Howse was talking about maximum possible optical RF errors - not average errors.

Use of centimetric radar (272/3) for gunnery purposes was not banned, but probably discouraged if alternate WS radars were not available. DoY was able to range continuously to 25500 yds using her Type 281 WA radar, in the GS role, and could probably detect large targets even further away when used in the WS mode.

User avatar
Dave Saxton
Supporter
Posts: 2926
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: British Type 284 gunnery radar

Post by Dave Saxton » Wed May 01, 2013 2:17 pm

I'm aware of the requirements for detecting and located ships laid down at the end of 1935, but the fact remains that there was little to no progress toward meeting the requirements prior to 1939. None of the pre-war R&D programs could have meant those requirements.
Pout states that 282/3/4/5 PRPs were in service use by spring-summer 1942.
I could be wrong, but in this case I believe Pout is in error. The Appropriate panel is not listed until 1943 and it is a feature of 284P models not installed in early 1942. In 1942 the M model was being installed. British radar nomenclature followed this patern:
MkII = M
MkIII = P
MkIV = Q

Also If the panel was in service during 1942 then why would the practice of supplimenting the ranges from Type 284 by Type 273 be needed? Tovey commented that the practice should be "gaurded against" but the temptation was "strong" to utilize 273 because it featured an excellent Precision Ranging Panel. No mention of the 284's ranging panel.
Use of centimetric radar (272/3) for gunnery purposes was not banned,


Perhaps banned is too strong of a word. But Tovey used strong wording when speaking against the practice. Tovey instructed that a "vigilant all around lookout" was "vital" and can not be "over stressed." His meaning is clear.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

dunmunro
Senior Member
Posts: 3376
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British Type 284 gunnery radar

Post by dunmunro » Wed May 01, 2013 10:28 pm

Dave Saxton wrote:I'm aware of the requirements for detecting and located ships laid down at the end of 1935, but the fact remains that there was little to no progress toward meeting the requirements prior to 1939. None of the pre-war R&D programs could have meant those requirements.
Pout states that 282/3/4/5 PRPs were in service use by spring-summer 1942.
I could be wrong, but in this case I believe Pout is in error. The Appropriate panel is not listed until 1943 and it is a feature of 284P models not installed in early 1942. In 1942 the M model was being installed. British radar nomenclature followed this patern:
MkII = M
MkIII = P
MkIV = Q

Also If the panel was in service during 1942 then why would the practice of supplimenting the ranges from Type 284 by Type 273 be needed? Tovey commented that the practice should be "gaurded against" but the temptation was "strong" to utilize 273 because it featured an excellent Precision Ranging Panel. No mention of the 284's ranging panel.
Use of centimetric radar (272/3) for gunnery purposes was not banned,


Perhaps banned is too strong of a word. But Tovey used strong wording when speaking against the practice. Tovey instructed that a "vigilant all around lookout" was "vital" and can not be "over stressed." His meaning is clear.
Naval Radar Panel meeting 16 December 1938:
Priority 1: Long range warning of aircraft (already largely met by Type 79Z...)...

Priorty 2: (a) Ship identification, from air and ship [IE surface warning - DM].
------------(b) range and bearing capabilities for surface gunnery
------------(c) range and bearing facilities for long range AA gunnery
Coales via Kingsley
Both type 279 and type 281 were pre-war designs and were capable of providing surface and AA gunnery ranges, with type 281 being capable of ranging to 28k yds. Both were fitted with a PRP to meet the requirements for surface and AA gunnery, and this was decision was made in Oct 1939 according to Coales. I've never read anything to suggest that RN naval radar was influenced by knowledge of Graf Spee's radar.

RA Burt provides a lengthy quote from Hood's type 284 radar trials in March-April 1941 at Scapa flow, which can be summarized briefly that continuous ranging was possible from 25000 yds and "spasmodic" ranging was possible out to 27200 yds using KGV as a target. The plot using the ranges beyond 25000 yds was still very accurate, showing that the ranges were still accurate. Hood's type 284 performance was very similar to KGV's during Bismarck's last battle.

The centimetric Type 273 (with it's stabilized antenae) was simply a better GS radar than type 284P in most areas except bearing accuracy, hence the temptation to use it in that role.

User avatar
Dave Saxton
Supporter
Posts: 2926
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: British Type 284 gunnery radar

Post by Dave Saxton » Thu May 02, 2013 2:45 pm

The centimetric Type 273 (with it's stabilized antenae) was simply a better GS radar than type 284P in most areas except bearing accuracy, hence the temptation to use it in that role.
Admiral Tovey said it was because of 273s PRP. Tovey's expanation makes sense because otherwise 273/M/P has no perfomance advantage on 284M.
Both type 279 and type 281 were pre-war designs and were capable of providing surface and AA gunnery ranges, with type 281 being capable of ranging to 28k yds.


These meters wave length air warning radars were not capable of doing those jobs very well. They were not useless- but just about. The main problem was the vertical lobes structure of meters wave length radar. The radar horizion to surface targets is therefore short, usually about 20km. 281 with 3.3 meters wave length being effective to surface targets to ~23km is plausable, but that's about it. To gain the greatest detection range 281 could use pulse widths up to 15 micro seconds. This gives a resolution for range of 2250 meters. Bearing resolution was 45* according to Friedman. Friedman may be in error (Callick reports 20* if the doublets were spaced one wave length), but it it going to be large, using such a small antenna at those wave lengths. Not very suitable for surface search or surface gunnery. They were perfectly suitable for ranging formations of high flying aircraft at great ranges, however. What they were designed to do. When Valiant used 279 in March 1941 for gunnery ranges at night, the reaction in the admiralty was: "big deal, the range was 7000 yards."
I've never read anything to suggest that RN naval radar was influenced by knowledge of Graf Spee's radar.

I have. R V Jones commented that Bainbridge-Bell's report was not widely circulated at the time due to secrecy protocols.

Examine the chronology of the important RN radar developments in the fields of surface search and naval gun laying. Its all post 1939. Callick describes 284 as the "RN's first fire control radar system" and its 1941 with a few provisional sets, and didn't really come of age until 1942-43.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

dunmunro
Senior Member
Posts: 3376
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British Type 284 gunnery radar

Post by dunmunro » Thu May 02, 2013 8:28 pm

Type 279 could range to 14k yds on surface and aerial targets, and KGV used her Type 279 against Bismarck from ~12k yds after her Type 284 broke down.

Regarding precision ranging and Type 284. The impression given is that only panels L22 and L24 provided precision ranging (~25yd), but that is not correct. DoY used a Type 284M(3) set at North Cape, in conjuction with both L12 (for splash spotting) and L18 (for ranging) panels. The L18 panel is described as a precision panel by it's designer C.A. Laws, so 284M did receive precision ranging panels despite the lack of the "P" suffix:
(6) "EMBODIMENT OF THE RANGING SYSTEM IN NAVAL
EQUIPMENT
The ranging system described has been incorporated in the
naval display panels LI3, LI7 and LI8, and has proved extremely reliable and consistent.
The overall accuracy depends
somewhat on the particular application but is in general a function
of three main factors. These are (1) error in crystal frequency,
(2) cyclic error of phase-shifter, and (3) setting error. The first
of these may be rendered negligible by a suitable choice of
crystal, the second has been shown to be less than 5 yd, and the
third, which depends (as in any system) on the nature of the
target, degree of fading, etc.; is usually less than 10 yd..."
A precision-ranging equipment using a crystal oscillator as a timing standard
Laws, C.A.
Electrical Engineers - Part IIIA: Radiolocation, Journal of the Institution of
Volume: 93 , Issue: 2
Digital Object Identifier: 10.1049/ji-3a-1.1946.0127
Publication Year: 1946 , Page(s): 423 - 440
IET JOURNALS & MAGAZINES
Additionally, the RN did not develop it's radar systems in isolation, but worked in close concert with the Army and RAF via various interservice radar development coordination committees; in fact Admiral Somerville worked as a inter-service radar liaison officer just prior and after the outbreak of war. The British Army was actively working on coast defence surface gunnery radar systems prior to Sept 1939, along with AA gunnery sets (GL Mk1), and worked closely with the Admiralty on these projects. GL MK1 formed the basis of Type 280, Type 279 and Type 281 and the RN was deploying Type 280 and Type 279 only a few months after the Army finalized the it's design. Type 282/4/5 was well along in design and testing prior to Dec 1939. RV Jones (p35-136) states that, in fact, Bainbridge-Bell's report on Graf Spee's radar aerials was largely ignored within the UK government and he doesn't state, AFAIK, that it had any influence on RN radar development. The design of Type 284/5 seems to have proceeded independently of outside influences, and developed logically in step with UK advances in radar power output (thus making 50cm viable as a long range radar) and ranging technology.

User avatar
Dave Saxton
Supporter
Posts: 2926
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: British Type 284 gunnery radar

Post by Dave Saxton » Thu May 02, 2013 11:03 pm

Type 282/4/5 was well along in design and testing prior to Dec 1939.
The record does not back up this statement.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

dunmunro
Senior Member
Posts: 3376
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British Type 284 gunnery radar

Post by dunmunro » Fri May 03, 2013 1:08 am

Dave Saxton wrote:
Type 282/4/5 was well along in design and testing prior to Dec 1939.
The record does not back up this statement.
(3) A RADAR RANGE-FINDER FOR POM-POM DIRECTORS
The number of directors in a modern warship, five in a light
cruiser, rising to 14 or more in a battleship (see Fig. 2), each
requiring its own range-finder, is such that it is clearly impossible
to find sufficient additional sites to fit remote-controlled aerial
systems. For this reason, it was evident before the war that it
would be necessary for each director to carry the aerial for its
own radar; this would also have the advantage that the aerial
would be kept pointing at the target engaged without the need
for any remote power control. Further, in view of the probability
of multiple targets and the necessity for ensuring that the
radar is ranging on the same target that the layer and trainer are
tracking, a narrow beam is clearly required. Therefore it was
recognized that, for gunnery purposes, the shortest possible
wavelength must be used, and with this in view a research group
at H.M. Signal School, Portsmouth, was working to produce
adequate performance in the decimetre waveband. By 1940,
new valves specially suitable for a pulse transmitter had been
developed in conjunction with the G.E.C. Research Laboratories,
and this had increased the output power available at 600 Mc/s
to 25 kW, 40 times that obtainable with two Western Electric
316A valves (the only type available when work on this wavelength
was begun in 1938).

Coales, Naval Firecontrol Radar.
AFAIK, it was the arrival of higher output power that allowed the transition to Type 284/5. The development of the larger aerial and the modified L12 ranging panel was a by-product of the higher output, but all the basic design features of type 282/3/4/5 were in place, awaiting the capability for higher output.

User avatar
Dave Saxton
Supporter
Posts: 2926
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: British Type 284 gunnery radar

Post by Dave Saxton » Fri May 03, 2013 4:15 am

(3) A RADAR RANGE-FINDER FOR POM-POM DIRECTORS
The number of directors in a modern warship, five in a light
cruiser, rising to 14 or more in a battleship (see Fig. 2), each
requiring its own range-finder, is such that it is clearly impossible
to find sufficient additional sites to fit remote-controlled aerial
systems. For this reason, it was evident before the war that it
would be necessary for each director to carry the aerial for its
own radar; this would also have the advantage that the aerial
would be kept pointing at the target engaged without the need
for any remote power control. Further, in view of the probability
of multiple targets and the necessity for ensuring that the
radar is ranging on the same target that the layer and trainer are
tracking, a narrow beam is clearly required. Therefore it was
recognized that, for gunnery purposes, the shortest possible
wavelength must be used, and with this in view a research group
at H.M. Signal School, Portsmouth, was working to produce
adequate performance in the decimetre waveband. By 1940,
new valves specially suitable for a pulse transmitter had been
developed in conjunction with the G.E.C. Research Laboratories,
and this had increased the output power available at 600 Mc/s
to 25 kW, 40 times that obtainable with two Western Electric
316A valves (the only type available when work on this wavelength
was begun in 1938).
Coales, Naval Firecontrol Radar.
This is essentially what I described in my first post. The 284 and 285 were developed from the 282 equipment post 1939. I would certainly not describe 282 as well advanced prior to 1940. The dating of the introduction of the key comonants that made up the design and others tell the storey of its advancement:

The micropup triode VT90 (NT90) was introduced in late 1939. Its output was an average of 5kw.

The micropup triode NT99 used by production models was not cleared for production until April 1941, and began production in summer 1941. This triode via anode modulation produced 25 kw peak in 1941 using the available pulser, 15 kw average output in service spec.

The pulser(Mercury Thyratron) CV 1145 became available in 1941

The pulser CV22 became available in 1942. This made more power available from the NT99 micropup triods via greater pulse power delivered to the anodes of the transmitter tubes. Power output then could be described as high powered with 60kw average output (125-150kw peak).

Display tube (A-scope) CV1097 became available in late 1940.

Display tubes CV1587 and CV964 became available by early 1942

Display tube CV 1522 became available late 1942 (what is the chronology of the upgrade panels to DOY's 284?)

Pulser CV 12 became available in early 1943. This pulser had a quicker rise time which was required for more accurate ranging. When the pulser fires it not only causes the transmitter to transmit, but the zero mark or the "big bang" is marked on the scope. It has to be the signal that pushes the pulser over the edge so to speak which marks the zero point on the indicator obviously and not the high voltage pulse itself. There is a random delay of the CV22s pulser's rise time between 0.5 micro seconds and 1.5 microseconds. Thus there is a random ranging error due to the random misalignment between the zero mark and the actual sending of the pulse's leading edge. As I understand it, the accuracy that Law is referring to is the accuracy of the electronic measurement between the null mark and the echo pip on the time base. The British attempted to develop more precise hydrogen thyratrons but failed. MIT succeeded during 1944. (Hohentwiel used a hydrogen thyratron from 1941.) late war radars such as Type 274 and the 400kw Seetakts, using spark gap modulators, had to use a trigger by the pulse itself to mark the zero point on a linear indicator. (Type 274 used the same PRP as the latest model PRP used by 284.)
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

dunmunro
Senior Member
Posts: 3376
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British Type 284 gunnery radar

Post by dunmunro » Fri May 03, 2013 4:59 am

This is essentially what I described in my first post. The 284 and 285 were developed from the 282 equipment post 1939. I would certainly not describe 282 as well advanced prior to 1940.
When Type 282 was tested on HMS Sardonyx it had all the essential features of the later variants - 50cm with Yagi antennae that was director mounted with the L12 ranging panel. Even with the low output it was able to range to 8km on ships:
In February 1937 J. F. Coales therefore proposed to transfer the centimetre wave work to 600 MHz (50cm) on which frequency he estimated existing triodes designed for c.w. work on 3-4m wavelength could be pulsed, and this was agreed. In April 1938 J. F. Coales was joined by H.C.Calpine who was given the job of developing the triode transmitter on 600MHz and the modulator for it, while C F Bareford developed the receiver and an A-scan display. Coales himself, assisted by W.F.Drury, developed the antennae, eventually settling on Yagi arrays. This development was later taken over by R V.Alred. By the end of 1938 all the essential components had been developed and an experimental set was installed at Southsea Castle. Trials using HMS Sardonyx as target were sufficiently promising to allow plans to be made for sea trials in HMS Sardonyx in June 1939. In these trials ships were followed out to 8km and low flying aircraft to 4500m
Radar Development to 1945 (Burns ed.) p.59.
So basically, it lacked sufficient power for effective long range surface gunnery, but 4.5km was quite sufficient for use as a pom-pom director and when higher power was available it was very straightforward to adapt the design for long range AA and surface gunnery.It must have been apparent to both it's designers and to the Admiralty that simply increasing the output, along with modest changes to the antennae and L12 panel, would result in an effective gunnery radar system. I don't think that there's any evidence that the Admiralty was suddenly inspired by KM radar to do what must have been painfully obvious, and what was already in the works for type 279 and 281 - namely long range gunnery.

User avatar
Dave Saxton
Supporter
Posts: 2926
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: British Type 284 gunnery radar

Post by Dave Saxton » Fri May 03, 2013 2:24 pm

Burns is wrong on this point. All the essential componants were not developed prior to 1940. Prior to 1940 282's development is not very impressive at all. Lets look at when the essential componants necessary for 282 becoming "well advanced" became available:

Receiver: CV16 signal amplifier valves-Early 1941. Local Oscillator CV82-1941. Mixer diode (vacuum tube replacing unreliable crystal) CV58-1942
Transmitter: NT-90 Triode available late 1939, NT99 availabe mid 1941. First Thyratron Modulator CV13 available mid 1940
TR switch: CV86 available early 1942
Data Display: CV1097 available late 1940.

Of course a single yagi for send and another for receive is hardly suitable for GS. No pig troughs or six yagi arrays until after 1939. One could also ask the question what good is pom pom director with a bearing resolution of 37*? What good is an air warning radar operating on 750cm with a compact doublet array for WS and/or GS? Not very. The RN record of acheivement in the field or radar R&D prior to Dec 1939 is shabby. Post Dec 1939 they really stepped up their game.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

dunmunro
Senior Member
Posts: 3376
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British Type 284 gunnery radar

Post by dunmunro » Fri May 03, 2013 5:33 pm

Dave Saxton wrote:Burns is wrong on this point. All the essential componants were not developed prior to 1940. Prior to 1940 282's development is not very impressive at all. Lets look at when the essential componants necessary for 282 becoming "well advanced" became available:

Receiver: CV16 signal amplifier valves-Early 1941. Local Oscillator CV82-1941. Mixer diode (vacuum tube replacing unreliable crystal) CV58-1942
Transmitter: NT-90 Triode available late 1939, NT99 availabe mid 1941. First Thyratron Modulator CV13 available mid 1940
TR switch: CV86 available early 1942
Data Display: CV1097 available late 1940.

Of course a single yagi for send and another for receive is hardly suitable for GS. No pig troughs or six yagi arrays until after 1939. One could also ask the question what good is pom pom director with a bearing resolution of 37*? What good is an air warning radar operating on 750cm with a compact doublet array for WS and/or GS? Not very. The RN record of acheivement in the field or radar R&D prior to Dec 1939 is shabby. Post Dec 1939 they really stepped up their game.
What you are describing are advances made in power output not changes to the basic design. There was simply no point in changes to the antennae until higher power was available, and when it became available the changes happened very rapidly, because these were minor variations on the original design. The essential elements in the way of target acquisition via director control, ranging and rate control were all in place, which is why it could move so quickly from trials to operational use once the needed power output was achieved.

User avatar
Dave Saxton
Supporter
Posts: 2926
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: British Type 284 gunnery radar

Post by Dave Saxton » Mon May 06, 2013 5:47 pm

???????? The British GS firecontrol couldn't rate with a range and a bearing? Data display is as basic as it gets. Any active radar system has that. It's the details of the transmitter, modulator, the reciever, the antenna...ect... that sets it apart from just any other radar system.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

Post Reply