Early RDF Type 284 Radar Performance

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Byron Angel
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Early RDF Type 284 Radar Performance

Post by Byron Angel » Fri Aug 02, 2019 9:58 pm

Some interesting information on the performance capabilities of the early marks of RDF Type 284 in surface gunnery applications

CB 4112 (4) (1942)
HANDBOOK ON THE USE OF R.D.F. FOR GUNNERY PURPOSES
TYPE 284
Admiralty Gunnery Branch, SW1 – Dated 19th July 1942.

quote -

RANGING CAPABILITIES
4. The results tabulated below show the average maximum usable ranges reported by the Commander-in-Chief, Home Fleet, from experience gained in the first five ships fitted with Type 284.

Target - - - - - - - - - - - - - - - Average Maximum Usable Range
Land Echoes - - - - - - - - - - - 50,000 yards
Battleship - - - - - - - - - - - - - 18,000 “
Large Cruiser - - - - - - - - - - - 15,000 “
Small Cruiser - - - - - - - - - - - 12,000 “
Destroyer - - - - - - - - - - - - - 8,000 “
Submarine on Surface - - - - - 5,000 “

Greater ranges can at times be obtained: for instance, ranges of an “Aurora” class cruiser have been taken at 28,000 yards when the Director Trainer could see the target and was keeping the aerials accurately trained, but the echoes in these cases are weak and fluctuating and cannot be relied upon in practice.

These ranges are somewhat less than were expected from the results obtained in the first sea trial referred to in Paragraph 1, and the possibilities of improving on them are still under investigation.

- unquote

Some other items of interest -
> In general, it was recommended that the range accuracy of the early Type 284 not be considered any better than +/- 150 yards.
> A range adjustment of 400 yards, on average, would be required to obtain a straddle.
> Transmission of range data was not automatically fed into the AFCT. Range was manually read/interpreted from the cathode ray trace by the "range reader" (radar operator) in the Type 284 office; he would pass the range reading to a companion sitting adjacent, who would pass it to the T.S. via electro-mechanical drum counter (see Paddon's account). Once it reached the T.S, the data would be input into the AFCT.

FWIW.

B

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Re: Early RDF Type 284 Radar Performance

Post by dunmunro » Sat Aug 03, 2019 3:02 am

These sound like ranges obtained from cruisers. Testing from Hood and actual results from KGV were somewhat better than those shown above.

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 trials performance was similar to KGV's during Bismarck's last battle.

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Re: Early RDF Type 284 Radar Performance

Post by Byron Angel » Sat Aug 03, 2019 2:36 pm

dunmunro wrote:
Sat Aug 03, 2019 3:02 am
These sound like ranges obtained from cruisers. Testing from Hood and actual results from KGV were somewhat better than those shown above.

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 trials performance was similar to KGV's during Bismarck's last battle.

Here is the preceding paragraph 1 from CB4112 (4) -
"Early trials of R.D.F. Type 282, which is the set designed for use against aircraft at short range, showed that with different aerials and minor modifications to the set results could be obtained on surface vessels at long range. After further experiment and one short sea trial with a temporary arrangement which confirmed early expectations, it was decided to modify a certain number of the Type 282 sets, already under construction, for use with the main armament of Capital Ships and Cruisers against surface targets."

My impression is that the early trials were largely "proof of concept" exercises, while paragraph 4 relates to practical experience at sea. Strictly my opinion, of course. YMMV.

Byron

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Re: Early RDF Type 284 Radar Performance

Post by dunmunro » Sat Aug 03, 2019 5:58 pm

Byron Angel wrote:
Sat Aug 03, 2019 2:36 pm
dunmunro wrote:
Sat Aug 03, 2019 3:02 am
These sound like ranges obtained from cruisers. Testing from Hood and actual results from KGV were somewhat better than those shown above.

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 trials performance was similar to KGV's during Bismarck's last battle.

Here is the preceding paragraph 1 from CB4112 (4) -
"Early trials of R.D.F. Type 282, which is the set designed for use against aircraft at short range, showed that with different aerials and minor modifications to the set results could be obtained on surface vessels at long range. After further experiment and one short sea trial with a temporary arrangement which confirmed early expectations, it was decided to modify a certain number of the Type 282 sets, already under construction, for use with the main armament of Capital Ships and Cruisers against surface targets."

My impression is that the early trials were largely "proof of concept" exercises, while paragraph 4 relates to practical experience at sea. Strictly my opinion, of course. YMMV.

Byron
During the Bismark episode we have good data from Hood (trials), KGV and Suffolk and all 3 ships recorded much longer ranges than the above average ranges.

During trials:
Trials in H.M.S. Nelson in June, 1940, showed that with an
aerial of this size a range of at least 20 000 yd on a battleship
could be expected with aerials at a height of 90 ft, the height of
the director control tower. It was therefore considered that the
use of radar ranging would give a worth-while improvement in
hitting power.
NAVAL FIRE-CONTROL RADAR*
By J. F. COALES, M.A., Associate Member,t H. C. CALPINE, B.A.,f and D. S. WATSON, B.Sc,
Associate Member.!
and from the above:
The surface equipment, Type 284, was first fitted on the
director control tower in H.M.S. King George V at a height of
90 ft in December, 1940. Trials of this set gave the following
maximum reliable ranges:—
Cruiser, Dido Class .. 20 000 yd
Destroyer, Town Class..14 000 yd
Destroyer, Hunt Class..12 000 yd
Submarine on the surface..7 000 yd


But if we include ranges from light cruisers and average them we might get something like the figures from CB4112 (4). However by Aug 1942 Type 284 had been improved considerably with the introduction of more powerful transmitters and more accurate ranging panels.

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Re: Early RDF Type 284 Radar Performance

Post by HMSVF » Sun Aug 04, 2019 10:36 pm

dunmunro wrote:
Sat Aug 03, 2019 5:58 pm
Byron Angel wrote:
Sat Aug 03, 2019 2:36 pm
dunmunro wrote:
Sat Aug 03, 2019 3:02 am
These sound like ranges obtained from cruisers. Testing from Hood and actual results from KGV were somewhat better than those shown above.

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 trials performance was similar to KGV's during Bismarck's last battle.

Here is the preceding paragraph 1 from CB4112 (4) -
"Early trials of R.D.F. Type 282, which is the set designed for use against aircraft at short range, showed that with different aerials and minor modifications to the set results could be obtained on surface vessels at long range. After further experiment and one short sea trial with a temporary arrangement which confirmed early expectations, it was decided to modify a certain number of the Type 282 sets, already under construction, for use with the main armament of Capital Ships and Cruisers against surface targets."

My impression is that the early trials were largely "proof of concept" exercises, while paragraph 4 relates to practical experience at sea. Strictly my opinion, of course. YMMV.

Byron
During the Bismark episode we have good data from Hood (trials), KGV and Suffolk and all 3 ships recorded much longer ranges than the above average ranges.

During trials:
Trials in H.M.S. Nelson in June, 1940, showed that with an
aerial of this size a range of at least 20 000 yd on a battleship
could be expected with aerials at a height of 90 ft, the height of
the director control tower. It was therefore considered that the
use of radar ranging would give a worth-while improvement in
hitting power.
NAVAL FIRE-CONTROL RADAR*
By J. F. COALES, M.A., Associate Member,t H. C. CALPINE, B.A.,f and D. S. WATSON, B.Sc,
Associate Member.!
and from the above:
The surface equipment, Type 284, was first fitted on the
director control tower in H.M.S. King George V at a height of
90 ft in December, 1940. Trials of this set gave the following
maximum reliable ranges:—
Cruiser, Dido Class .. 20 000 yd
Destroyer, Town Class..14 000 yd
Destroyer, Hunt Class..12 000 yd
Submarine on the surface..7 000 yd


But if we include ranges from light cruisers and average them we might get something like the figures from CB4112 (4). However by Aug 1942 Type 284 had been improved considerably with the introduction of more powerful transmitters and more accurate ranging panels.


Daft question....


Do atmospherics make a difference to radar performance?

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Re: Early RDF Type 284 Radar Performance

Post by Byron Angel » Mon Aug 05, 2019 12:20 am

Hi Dunmunro,
> Tovey's report CB 4112(4) dates about a year after the early Nelson and Hood tests and purports to specify "maximum usable ranges" as opposed to maximum possible ranges, which implies analysis of data accumulated from sea service and battle practices. For example, from what I have read, successful employment of RDF Type 284 for surface gunnery control required a good deal of close coordination between DCT and the "radar office" to keep the antennae exactly upon the target. This suggests to me that we are not talking the raw performance characteristics of the device itself, but its actual performance within a ship's integrated gunnery control system.
> The fact that CB4112(4) was issued under the auspices of Tovey himself as Admiral, Home Fleet suggests that it must have been perceived to represent information useful and/or important to the fleet. It is to my mind difficult to reach a conclusion that, because its presumably more recent data materially differs from that given in earlier reports, it may be disregarded as erroneous.

Not trying to cause a big sensation. Just saying.

Byron

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Re: Early RDF Type 284 Radar Performance

Post by Byron Angel » Mon Aug 05, 2019 12:24 am

Daft question....
Do atmospherics make a difference to radar performance?
Yes. Meteorological conditions and other anomalies (such as atmospheric ducting), even sea state to a degree, can influence radar performance.

Byron

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Re: Early RDF Type 284 Radar Performance

Post by Dave Saxton » Mon Aug 05, 2019 1:15 am

Ellis reported that the 284 on Suffolk could hold the Bismarck out to an absolute maximum of 13 miles on occasion. Examination of the records of the shadowing, indicate that contact was regained in most cases after resting the set, or if contact had been lost, at about 18,000 yards.
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.

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Re: Early RDF Type 284 Radar Performance

Post by dunmunro » Mon Aug 05, 2019 2:09 am

Byron Angel wrote:
Mon Aug 05, 2019 12:20 am
Hi Dunmunro,
> Tovey's report CB 4112(4) dates about a year after the early Nelson and Hood tests and purports to specify "maximum usable ranges" as opposed to maximum possible ranges, which implies analysis of data accumulated from sea service and battle practices. For example, from what I have read, successful employment of RDF Type 284 for surface gunnery control required a good deal of close coordination between DCT and the "radar office" to keep the antennae exactly upon the target. This suggests to me that we are not talking the raw performance characteristics of the device itself, but its actual performance within a ship's integrated gunnery control system.
> The fact that CB4112(4) was issued under the auspices of Tovey himself as Admiral, Home Fleet suggests that it must have been perceived to represent information useful and/or important to the fleet. It is to my mind difficult to reach a conclusion that, because its presumably more recent data materially differs from that given in earlier reports, it may be disregarded as erroneous.

Not trying to cause a big sensation. Just saying.

Byron
If we include ranges from light cruisers, whose DCT mounted radar antennae were ~33% lower in height than a battleship's, then the ranges make sense, but they are not representative of actual ranges obtained by battleships in trials or in combat.

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Re: Early RDF Type 284 Radar Performance

Post by wadinga » Mon Aug 05, 2019 1:17 pm

Fellow Contributors,

This statement is 100% correct if, perhaps IMHO, a little understated:
Yes. Meteorological conditions and other anomalies (such as atmospheric ducting), even sea state to a degree, can influence radar performance.
Yes hugely affect, we cannot talk about absolute guaranteed deliverable values but performance in prevailing conditions. Variations in temperature of the components and their aging through use, would also affect performance and require constant tuning and tweaking to extract optimum performance. Identifying "drop-off" in performance would be difficult, you need to know you are not seeing something you should be able to see. :shock: I expect Tovey's document is fairly conservative.

In the "Improvements in Gunnery" document 1942 it says

"Reliable echoes of single splashes have been obtained as follows": 14" with Type 274M (I) 16,000 yds, the same with 273 Mk III, but 25,000 yds with the later Mk IV version. These were with practice projectiles and the speculation was that explosive ones would create longer lasting splashes.

Delightfully it says "the projectiles themselves can be followed out, looking like a mouse moving under a sheet, nearly as far as the above ranges with RDF Type 284M (I), and to about 9,000 yds with Type 273." It blames the narrower vertical beam for the latter's performance. The "sheet" would be the flat trace at the bottom of the "A" scope graphical display, and the "mouse" a moving peak travelling outwards until it merged with the target peak.

It notes with current pulse lengths that splashes 100 yds short to 400 yds over are "drowned" in the target echo.

Paddon's insistence that he was seeing three targets at Denmark Straits shows that even the most Senior Radar officer aboard could be misled.

All the best
wadinga
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Re: Early RDF Type 284 Radar Performance

Post by Dave Saxton » Mon Aug 05, 2019 3:40 pm

Tovey's report is valuable because rather than based on tests of small sample size, it is compiled from a larger sample size of empirical observations during operations of the fleet. It therefore represents a real world average. Included in that average would be sets mounted on both cruisers (a larger number) and battleships.

There is not a large disparity between the range performance of radar sets mounted on cruisers and those mounted on battleships, but there is a differential. The early version of 284 is listed as having a reliable range, battleship to battleship, of 20,000 yards. Later models such as type 284M are listed as having a max battleship to battleship range of ~29,000 yards.

Among the improvements of the later marks of 284 was common mode operation of the antenna and greater transmitted power. Between those two factors the improvement of antenna gain is the far more important. It takes massive increases of transmitter power to effect significant improvement in range attainment. For example, it requires a 16 fold increase in transmitter power to effect a doubling of range attainment. On the other hand an effective doubling of antenna size can effect an 30% improvement of range by itself. Another more effective factor for improving radar performance is to improve the signal noise ratio of the receiver.

The range of which shell splashes can be detected and also the range that very small sized objects can be detected is a function of the signal to noise ratio. One of the challenges found was the inherent noise of vacuum tube components used in receivers. The noise level began to gradually overcome that of the signal after the operating frequency passed above 400mhz. 284 operated at 600mhz. They did an interesting work around of this problem.

Instead of connecting the cathode or the anode to ground, they connected the grid to ground. This did not eliminate the noise, but reduced it to the point that it was acceptable at 50cm.

Increasing the wave length was another possible alternative and would have much more significantly improved the range attainment and significantly improved the ability to spot small objects and shell splashes, but the trade off would have been a wider beam given the antenna size. Type 284's beam width was actually only 3 degrees. ( Calick)

An additional method of improving signal to noise ratio was make the bandwidth in megahertz of the receiver the inverse of the pulse width in micro seconds. However, this technique was not known to Allied scientists and engineers at that time.
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.

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Re: Early RDF Type 284 Radar Performance

Post by Byron Angel » Mon Aug 05, 2019 5:44 pm

dunmunro wrote:
Mon Aug 05, 2019 2:09 am
If we include ranges from light cruisers, whose DCT mounted radar antennae were ~33% lower in height than a battleship's, then the ranges make sense, but they are not representative of actual ranges obtained by battleships in trials or in combat.

A couple of thoughts -

> CB4112(4) mentions that its performance assessment was based upon experience with the first five ships fitted with Type 284 radar. What would those ships have been? I'm guessing - HOOD, KING GEORGE V, PRINCE OF WALES, RENOWN, REPULSE.

I suspect that the disconnect here is likely related to the dual roles of Type 284: both surface search radar and gunnery control radar. CB4112(4) is titled - HANDBOOK ON THE USE OF R.D.F. FOR GUNNERY PURPOSES, TYPE 284, Admiralty Gunnery Branch, SW1 – Dated 19th July 1942 - and therefore arguably addresses the Type 284 in relation to its performance as a gunnery control radar (as opposed to a search radar.

Byron

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Re: Early RDF Type 284 Radar Performance

Post by dunmunro » Mon Aug 05, 2019 7:05 pm

Byron Angel wrote:
Mon Aug 05, 2019 5:44 pm
dunmunro wrote:
Mon Aug 05, 2019 2:09 am
If we include ranges from light cruisers, whose DCT mounted radar antennae were ~33% lower in height than a battleship's, then the ranges make sense, but they are not representative of actual ranges obtained by battleships in trials or in combat.

A couple of thoughts -

> CB4112(4) mentions that its performance assessment was based upon experience with the first five ships fitted with Type 284 radar. What would those ships have been? I'm guessing - HOOD, KING GEORGE V, PRINCE OF WALES, RENOWN, REPULSE.

I suspect that the disconnect here is likely related to the dual roles of Type 284: both surface search radar and gunnery control radar. CB4112(4) is titled - HANDBOOK ON THE USE OF R.D.F. FOR GUNNERY PURPOSES, TYPE 284, Admiralty Gunnery Branch, SW1 – Dated 19th July 1942 - and therefore arguably addresses the Type 284 in relation to its performance as a gunnery control radar (as opposed to a search radar.

Byron

As of 28 Sept 1941, 7 capital ships and 16 cruisers had been fitted with type 284. - Howse, p.101.

Neither Renown nor Repulse had radars as of 27 May 1941. According to Howse the first 5 operational type 284s fitted to Battleships were Hood, KGV, PoW, QE and probably Nelson.

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Re: Early RDF Type 284 Radar Performance

Post by Byron Angel » Mon Aug 05, 2019 7:24 pm

dunmunro wrote:
Mon Aug 05, 2019 7:05 pm
According to Howse the first 5 operational type 284s fitted to Battleships were Hood, KGV, PoW, QE and probably Nelson.
Is it possible to ascertain with any confidence whether those ships were likely the first five ships on any class so fitted?

B

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Re: Early RDF Type 284 Radar Performance

Post by dunmunro » Mon Aug 05, 2019 8:19 pm

Byron Angel wrote:
Mon Aug 05, 2019 7:24 pm
dunmunro wrote:
Mon Aug 05, 2019 7:05 pm
According to Howse the first 5 operational type 284s fitted to Battleships were Hood, KGV, PoW, QE and probably Nelson.
Is it possible to ascertain with any confidence whether those ships were likely the first five ships on any class so fitted?

B
According to Howse these cruisers had been fitted with type 284 up to May 1941:
Aurora - May
Fiji - March
Liverpool - March
Neptune - May
Suffolk - Feb

Exeter had probably been fitted by this time as well and these fitment dates would be interleaved with battleship dates. AIUI, the key factor was availability of the ship in a suitable yard rather than priority by ship class. Suffolk received Type 284 before Hood and PoW and about the same time as QE. KGV (Dec 1940) and Nelson (experimental set mid 1940) were the first two to receive Type 284.

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