Type 984 and Type 988 radars

[Rule of cool]

I have some questions for the rad-techs on these old 3D radars.

The Type 984 had 5 radar feed-horns transmitting through the Luneburg lens, 4 of these feed-horns were moved vertically through 5 degrees by mechanical servos. I've read that there was an idea/concept/proposal/plan to update this radar with solid state electronics and electronic scanning, which I presume means in the vertical with the horizontal taken care of by rotation.

Can electronic scanning be done with these 4 feed-horns? Or would/could they be replaced with a phased array transmitter that would transmit phased pulses through the Luneburg lens? The contemporary SPS39 appears to have a phased array transmitter using a conventional-ish curved antenna, so I suppose it's technically possible. IIUC the 984 had multiple magnetrons so presumably they could power a new antenna/transmitter.

With the Type 988/SPS-1, it's described as a 3D, but looking at what's under the dome in the Tromps there appears to be 2 radars each with 2 transmitters. Obviously the planner arrays are 3D and that is described at the Target Tracking Radar, but what about the parabolic antennas; are they 2D search radars? What about the slotted waveguide antenna, what does it do?

How fast does the SPS-1 rotate? The radars it was supposed to replace in British service rotated at 10 and 30 rpm. Presumably with 2 arrays the TIR radar could rotate at 15rpm and get the same picture, but 15 rpm for a 2 antenna search radar is a lot.

Any insight would be appreciated.

SPS-1 - Radartutorial

www.radartutorial.eu

https://www.shipsnostalgia.com/media/type-984-radar.205416/

AN/SPS-39 - Radartutorial

www.radartutorial.eu

 

[Hobbes]

From Friedman's Naval Radars:

SPS-01 was designed to meet the mutually contradictory requirements of search and multiple-target tracking. For search, it had to radiate over a very wide volume, with a relatively low data rate for long ranges and a higher one for short range; accuracy could be sacrificed for a high probability of target-detection. For tracking, on the other hand, precision was necessary, coupled with a concentration of radiated energy in the direction of the target, and a very high (or, better, continuous) data rate.Discussions with the Royal Netherlands Navy began in 1958, the goal being simultaneous high-precision tracking of multiple targets; SPS-01 is now credited with the capability to handle over a hundred aircraft tracks. Research began in 1959, and a first working model was available in February 1964. At that time the production of two systems began, the first beginning tests in 1967. They were completed in 1969, and two SP-01s have been installed aboard the two Dutch guided missile frigates (destroyers) of the Tromp class. The MTTR project was for a time a joint one with Great Britain, and a variant (Type 988, or 'Broomstick') was intended for the Type 82 missile destroyer (Bristol) and for the abortive British carrier project (CVA-01).

The radar employs six antennas, all mounted together on a stabilized base and rotating together at 20 rpm: two paraboloids back-to-back, with feed horns moving to generate any of five alternative beams plus a sixth (fixed)low-angle beam; two back-to-back FRESCAN arrays at right angles to the parabolas; a multi-element antenna for high-angle search (omitted in production models); and a slotted waveguide for IFF mounted below one of the parabolas. In operation, the low-angle search beam is operated continuously to provide short-range warning with a high data rate (40 scans per minute). The other five beams are energized in sequence one by one during successive rotations, so that for each one the data rate is reduced to 8 per minute. The net search pattern is a cosecant-squared shape, but avoids the drawbacks of a more conventional fan-beam radar, ie low antenna gain and great susceptibility to clutter and jamming. Beam dimensions vary with elevation: in each case the paraboloid assures a horizontal width of 1.5° but the vertical beam size varies between 2° at an elevation of 2.5° to 30° at an elevation of 21°. Targets are detected automatically and their two-dimensional coordinates fed into the central computer, which instructs the two FRESCANS to find them in three dimensions for tracking.

Each of the FRESCANs consists of a series of slotted waveguides slanted to the horizontal, and fed by the usual sinuous waveguide for vertical scanning. The slant makes it possible for the system to perform a true vertical scan while the antenna rotates rapidly; in effect the FRESCAN can be used to scan both vertically and horizontally, and thus to obtain precision target data. Approximate beam dimensions are 1.5° x 1.5°, the latter depending on beam elevation. Back-to-back positioning provides a very high data rate of 40 scans per minute.In operation, the computer first ascertains that a target detected in two dimensions is not already being tracked.It then programs a frequency sweep which measures target elevation; on the next scan the frequency variation is programmed to give a horizontal scan for precision target-bearing location. Each target is scanned cross-wise atthe rate of twenty measurements per minute. In this way a pure FRESCAN is used for true three-dimensional tracking, without phase shifters; however, its effective tracking rate is limited by the requirement for mechanical rotation.

The system as a whole operates in S-band, the frequency ranges of the paraboloids and the two FRESCANs differing slightly. A single power source produces 40-microsecond, 750kW pulses with staggered PRFs of 460 and 540, and energy is presumably time-shared among the antennas.

 

[Rule of cool]

Thanks for that, I'm going to have to read it a few more times to digest what it means in practice.

 

[zen]

Type 984 at Marconi

Marconi Radar History / Naval Radars

Arguably one could replace mechanical motion for electrical scanning?
....however the use of separate magnatrons for each beam, would immediately be queried.

 

[Rule of cool]

Type 984 at Marconi

Marconi Radar History / Naval Radars

Arguably one could replace mechanical motion for electrical scanning?
....however the use of separate magnatrons for each beam, would immediately be queried.

Thanks for that link, as usual the devil is in the details so I'm using the 988 info Hobbes provided and inserting the 984, 965 and 992 tech details so I can compare.

With the magnetrons I'd think its better have them and not need them then need them and not have them.

I don't understand how electronic scanning occurs from a single feedhorn.

 

[zen]

This might help as it helped me a bit.

Radar Types

British, American, German and misc radar types and descriptions

www.radarpages.co.uk

Possible option for each transmitter in a simplified form.

Serpentine Feed - Radartutorial

www.radartutorial.eu

 

[datafuser]

I have some questions for the rad-techs on these old 3D radars.

The Type 984 had 5 radar feed-horns transmitting through the Luneburg lens, 4 of these feed-horns were moved vertically through 5 degrees by mechanical servos. I've read that there was an idea/concept/proposal/plan to update this radar with solid state electronics and electronic scanning, which I presume means in the vertical with the horizontal taken care of by rotation.

Can electronic scanning be done with these 4 feed-horns? Or would/could they be replaced with a phased array transmitter that would transmit phased pulses through the Luneburg lens? The contemporary SPS39 appears to have a phased array transmitter using a conventional-ish curved antenna, so I suppose it's technically possible. IIUC the 984 had multiple magnetrons so presumably they could power a new antenna/transmitter.

With the Type 988/SPS-1, it's described as a 3D, but looking at what's under the dome in the Tromps there appears to be 2 radars each with 2 transmitters. Obviously the planner arrays are 3D and that is described at the Target Tracking Radar, but what about the parabolic antennas; are they 2D search radars? What about the slotted waveguide antenna, what does it do?

How fast does the SPS-1 rotate? The radars it was supposed to replace in British service rotated at 10 and 30 rpm. Presumably with 2 arrays the TIR radar could rotate at 15rpm and get the same picture, but 15 rpm for a 2 antenna search radar is a lot.

Any insight would be appreciated.

SPS-1 - Radartutorial

www.radartutorial.eu

https://www.shipsnostalgia.com/media/type-984-radar.205416/

AN/SPS-39 - Radartutorial

www.radartutorial.eu

Some info on the MTTR.

 

[Rule of cool]

Thanks for the replies, I've started putting some stats for the Type 984, 965 and 992 into the excerpt from Friedman that Hobbes provides and I have to say I'm pretty impressed with the SPS-01. What's more the unit was installed on ships on similar size to the Type 42 destroyer rather than being reserved for the big Type 82 and CVA01 which the Dutch didn't have. I can't help but think that if it was adopted it would replace all 3 earlier radars in RN service, even on the Type 42s.

 

[zen]

It seems the Admiralty thought otherwise.
ASWRE also thought otherwise.
They pointed out if relaxed weight and size constraints to allow Broomstick, then their antenna design in S-Band would be better. That their design in C-band was driven by those constraints and would deliver the desired performance.
Type 988 Broomstick was chosen to buy favour with the Dutch. Likely related to efforts to sell Sea Dart to them and garner support for EEC entry.

On use of multiple magnatrons in radar.
Rereading some descriptions, it seems possible multiple transmitters were sometimes used in some radars to bolster the signal output and gain increased range.
This might allow a revised Type 984 to be redesigned to take advantage of this option.

 

[Rule of cool]

It seems the Admiralty thought otherwise.
ASWRE also thought otherwise.
They pointed out if relaxed weight and size constraints to allow Broomstick, then their antenna design in S-Band would be better. That their design in C-band was driven by those constraints and would deliver the desired performance.
Type 988 Broomstick was chosen to buy favour with the Dutch. Likely related to efforts to sell Sea Dart to them and garner support for EEC entry.

On use of multiple magnatrons in radar.
Rereading some descriptions, it seems possible multiple transmitters were sometimes used in some radars to bolster the signal output and gain increased range.
This might allow a revised Type 984 to be redesigned to take advantage of this option.

I'd be interested to throw the details of the ASWRE C-band* radar into the mix, any techno-babble you have would help as I can put it alongside what I have for the Types 965, 992, 984 & 988. For starters we know it operates in the C band as opposed to the SPS-01, 984 and 992 which were S band and 965 which was P band.

If the Admiralty and ASWRE thought the Type 998, with its 6 antennas and S band, was too big for the Type 42 does that mean C band radars are intrinsically smaller or was the ASWRE radar less comprehensive?

*Presumably this is the older IEEE C band, as the newer NATO one doesn't have an S band.

 

[zen]

I cannot quite organise myself in searches at the moment. But there be substantial threads on NIGS that touch on this topic.
JCF Fuller did sterling work digging out details.

https://www.secretprojects.co.uk/threads/rn-nuclear-nigs-ship.8253/page-7

 

[EwenS]

Type 984 at Marconi

Marconi Radar History / Naval Radars

Arguably one could replace mechanical motion for electrical scanning?
....however the use of separate magnatrons for each beam, would immediately be queried.

While the article says it came from a internet forum and the original source is unknown and should be treated with caution, it is in fact attributable to Norman Friedman and is a direct quote from his "Naval Radar" book published back in 1981.

 

[Rule of cool]

Before I go into any detail something is bothering me; is the designation Type 985 used twice for 2 different concepts? I've seen it used for the NIGS radars, which I understand to be plannar arrays like the US SCANFARs but I've also seen it used to describe a modernised Type 984 with solid state electronics and electronic scanning (presumably in the vertical).

 

[zen]

Before almost anyone noted things in the margins of Friedman or dug out obscure books on British radar. Or better yet trawled through the archives.
Most people assumed Type 985 would just be a continuation from Type 984.
And this has stuck around because most people think that because the UK lagged in radar products compared to the US. That it somehow lagged in theory.

But this, like with computers, which for decades was claimed as US invention by certain US companies. Was in the absence of any contradicting information. Taken as gospel.
After all the experience of WWII and after seems on the face of it to just be one of being completely outperformed by the US in every way.
And Americans be not backward in coming forward with their achievements.

So the 'cultural cringe' towards all things American has shaped the prevailing assumptions about the UK amongst it's own population. After all everything in American culture feeds across without a language barrier and only deeply entrenched tradition holds the line.

Old folks who didn't ascribe to this, were just assumed to be out if date, ignorant and not modern.

But truth will out....until we get all 1984 on things. So now we see the truth emerges.
We didn't lag in theory. At times our theoretical work, despite the lack of funds, is ahead of the Americans.
Even perhaps to this day.
And equally in a world where information is shared across military and scientific realms. Is it that surprising that the truth is often a convoluted intertwining of American, British and European, even Russian and beyond.

 

[Rule of cool]

It seems the Admiralty thought otherwise.
ASWRE also thought otherwise.
They pointed out if relaxed weight and size constraints to allow Broomstick, then their antenna design in S-Band would be better. That their design in C-band was driven by those constraints and would deliver the desired performance.
Type 988 Broomstick was chosen to buy favour with the Dutch. Likely related to efforts to sell Sea Dart to them and garner support for EEC entry.

I've had a read of https://www.secretprojects.co.uk/threads/rn-nuclear-nigs-ship.8253/page-7 (what a wealth of info!) and correct me if I'm wrong but it doesn't appear as if the British had any applicable radar post Types 984/965/992 that were ready for production.

It's not as if there was a radar prototype that was ready to go and was narrowly beaten out by the SPS-01 due to dastardly politics, like the TSR2-F111K and all the other tragic episodes. After all, rather than picking up where they left off with British radars when the Type 988 was cancelled, they stuck with the ratty old Type 965/992 and ditched the 984.

In any case the Dutch designed the SPS-01 for a destroyer sized ship and while I'm sure the Admiralty and ASWRE would have loved a bespoke destroyer radar the RN could have muddled through fitting the Type 988 to the Type 42 analogue if it was adopted. It seems a cheap way to get a very capable radar system in a vindictive financial environment.

 

[zen]

Ok then we simply interpret the information differently.
To my reading ASWRE was undermined by politics and there's nothing to imply they couldn't achieve product in a similar timescale.
It must be born in mind that any savings assumed by opting for Type 988 Broomstick is potentially undermined by the requirements that imposes on the creation of Type 909 Desertcar.

The assumption that SPS-1 with DAISY is the same as Type 988 with ADAWS is not viable.

Increasingly through the period, Broomstick was reduced to Type 82s and the carriers.
Whereas ASWRE C-band effort is applicable to the bulk of the fleet.

 

[Rule of cool]

From Post #2 re the SPS-01.
"Research began in 1959, and a first working model was available in February 1964. At that time the production of two systems began, the first beginning tests in 1967. They were completed in 1969,"

IIUC the British recommended getting on board with the 998 in 1962 and officially did so in 1964, at which point a working model was available. Was a working model of the ASWRE C-band radar available in the 1964-65 timeframe?

In the Type 82 and 42 ships a target was detected by the Type 965, tracked by the Indicated by the Type 992 and tracked and illuminated by the Type 909. With the Type 988 the target would be detected by the 2D antennas and indicated by the 3D FRESCAN antennas, why would the Type 909 need to be more expensive? Also the Type 82 and CVA01 which were to have the Type 988 also had ADAWS 2 & 3, why couldn't the Type 988 be integrated into the ADAWS 4 of the later Type 42?

BTW I'm looking through the SIGS threads now, I'll get to the bottom of this even if it kills me!

 

[zen]

I don't know how far funding of practical elements got. ASWRE fumed a bit over the matter.

The lower quality of resolution using S-Band on Type 988 imposed a higher demand on the Illuminating radar system. This got even worse when using Type 960 and 965, and even worse when using J-band for guidance of Sea Dart.
Result is greater cost/weight/power for Type 909.
If memory serves the lightweight set later developed was a 6ft cassegrain aerial (and the basis of the Vulcan armed with Sea Dart), but I dimly reccal the 909 as 8ft diameter.

The higher quality resolution using C-band obviated such a need and like some versions of NIGS ought to only need a 4ft aerial of a lighter less costly system.

Good luck with your reading.

 

[Rule of cool]

Good luck with your reading.

The hardest part is working out what progressed to hardware, there's so much material on what were essentially concepts discussed at meetings.

 

[Rule of cool]

One I thing I think is missing in all the discussions around NIGS, SIGS and all the radars is the little weapon that could('nt); Sea Cat.

Like it or not the Sea Cat ticked the point defence SAM box from about 1961-62, just about the time NIGS was dropped and SIGS went long range.

In 1962 without the need for a radar system to guide a point defence missile the RN's immediate future radar requirements were simplified to replacing the Type 965, 992 TI and 984 3D radars in future carriers and CF.299 carrying escorts. They plumped for the Dutch radar under development that appeared to be able to meet the requirements, or close enough anyway, and started negotiations for the joint project. The SPS-01 radar prototype was ready in Feb 1964 and the MoU was signed in May 1964.

Where was the Type 909s development at in 1962-64? Was its development driven by the Type 988?