Expanding horizontal coverage and for IRST triangulation, not to extend range of a single radar.
Ok. I admit defeat. I’d rather cut this off here and get back to productive topics instead of this back and forth stuff for days on end. We will see who’s right if/when I get the MDR Information. It won’t serve much purpose ingame anyway.
The APG-71 was at the cusp of AESA technology, so it can be assumed that AESA wouldn’t be compatible/wouldn’t need such a capability.
Well, i’ve found many s–ts that explain how it can be done with mathematics that i can’t explain and actually it’s early morning here and i don’t want to even punish my brain with all that…
BUT:
MIMO.
And power-aperature product. Something has to do with this.
Too much power for one antena , but with MIMO via datalink can bypass the limitation.
It’s not a APG-71 thing or whatever,it just happen because the transmiter has the power to do it, while for example in a F-16s radar doesn’t.
In general in radars, the equipment limitations are defined by transmiter power and antenna size , you can use MIMO to bypass the antena size problem , when you have the transmiter power.
@MikeyPlayzonYT
Question. There is a NATOPS/ NAVAIR for F-14D , NAVAIR 01−F14AAD−1A , can’t they use it to bring the plane? Or is it of the stuff that are classified , but are everywhere on the internet?
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There are actually methods of connecting radars through datalink to increase the detection range (particularly against low observability targets). Russia uses them on some SAM systems, there are rumors the US has tested it, and other countries like Japan have prototyped systems which use it.
However, it’s basically impossible to do for flying platforms, it takes fairly precise positioning information and really advanced time sharing protocols, which, as advanced as it was for the time, was well beyond the capability of the F-14’s microprocessor. And even if it was, the accuracy of positioning information needed is well beyond what any inertial or GNSS system of the time (or even now) could provide for a moving platform.
They’re called MIMO (Multiple-input multiple-output) radars, most existing versions for military use, like what russia uses, are specifically a variety called multistatic radars, key emphasis on static, it’s basically impossible to have them on moving things due to what I said earlier.
In reviewing the evolution of RWR systems in US Navy/Marines service, I came across an interesting detail regarding the ALR-45F. This variant, fitted to platforms like the AV-8C, F-4S, and A-7Es, appears to be functionally near-identical to the ALR-67. Essentially, it seems the ALR-45F was a retrofit package, embedding ALR-67 electronics into legacy ALR-45 installations, likely to minimize structural modifications while bringing older airframes up to then-current EW standards.
That raises the question… did the F-14A ever receive the ALR-45F? Given that by the mid 1980s the original ALR-45 was already outdated, it seems possible. The ALR-67, by contrast, was standard on F-14B and D models, and select F-14As were retrofitted with ALR-67 starting around 1995–96.
Has anyone come across documentation or maintenance records indicating that any F-14As operated with the ALR-45F during the interim, except secondary documents? Or was it essentially skipped in favor of direct ALR-67 upgrades?
That manual seems like it is classified, you can find other documents mentioning it but you can’t find it.
That manual has information about the Radar, DL, Irst, Weapon system, EW suite and a few more things
MIMO is for locally connected antennas
You have to feed the high power RF output of the transmitter to the antenna
And that’s not something you can “datalink” (well, because it’s not “data”; It’s high power RF)
It’s kinda like trying to download water through WiFi …
You could theoretically “sync” two nearby radars for double the transmitted power, but (apart from its practical difficulties) double the power will only increase your range by less than 19% …
It’s classified and all examples of them existing are heavily redacted. That’s why I sent the MDR.
Multi-static radars have a larger net gain then 19% due to how they cross reference received information. But, yeah, for the original point, the accuracy of information and timesharing systems needed for it is not feasible for fighter jets, particularly of the era of the F-14
Multistatic radars don’t increase the range in the way being discussed here (I.e. both radars being next to each other, but seeing further)
They work in a similar way to how datalinked Tomcats or other aircrafts would work.
By having more radars on the ground (or in the air) in various places to cover a larger area.
Or by looking at targets from more favorable aspects that have higher RCS (E.g. Side aspect).
Or eliminating blind spots that some of the installations might have by covering the area from different angles.
As far as absolute detection range is concerned you are still limited by the same minimum detectable signal of each individual radar.
Because signal amplification and processing is done separately in each radar.
I.e. if me and you are standing in some yard and listening for suspicious sounds, if we spread out we can cover a larger area.
And if we have some form of communication (datalink) we can cross reference what we hear to for example eliminate blind spots or false targets or background noise etc
But we are still limited by the smallest signal/sound that either of our ears and brains can detect.
It’s not like we can hear quieter sounds from further because we have 4 ears in total …
(Because signal amplification and processing is done separately and the received signals can’t be summed together in their raw form … Because for them to be shared through the “datalink” they have to go through that local amplification and processing step first, so the same limitations remain)
Aren’t they capable of combining signals for an increased effective range in the same manner of how they cancel out interference? ie. when two or more radars in a set are comparing information for a specific location, when cross comparing them to see if one is eronious or which signal is clearer; additionally doing additive comparisons to see if it would bring the result for a particular location above the noise floor? I know systems can use this kind of operation, certain methods of drone detection using camera arrays use the same kind of function to drastically increase range and accuracy.
I’m not entirely too knowledgeable on multi-static radars tbf, all i know of were some very recent prototypes which were specifically testing things like this, i have no idea if this is in the realm of currently in service stuff or not.
Edit: an example with cameras for aircraft detection
You are thinking at a higher level, yes you can combine the information to increase the quality of detection.
But at a lower level (circuit level), each radar is still limited by their signal amplifiers and comparators etc
I.e. for me and you to share information about what we hear, we first need to be able to individually hear that thing.
And that’s determined by the smallest signal that our ears and brains can detect and process …
I.e. the “minimum detectable signal” in the radar range equation:
Now, you can theoretically “sync” the two transmitters (their frequency, phase, PRF, where they are pointed at, …) to double your transmitted power, which in theory will (at most) double the power that each receiver receives.
But even this will in theory result in less than 19% of increase in range.
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But they can still compare signals from below individual minimum detectable signals? Like, RF imaging can produce results like this where there’s background noise below what can be identified as targets, but is still usable to be added together with other images from other radars even in this form.
There are methods of signal processing which work from below the regular noise floor for target identification, stuff like radars adding up individual frequency returns over multiple beam passes.
like this
The system itself is capable of a 460-mile (740 km) range, but the antenna design limits this to only 230 miles (370 km). Use of datalinked radar data allows two or more F-14Ds to operate the system at its maximum range. what does this mean?
ChatGPT said:
Got it! Let me break this down further and explain what that statement means in the context of the APG-71 radar system.
Key Concepts:
- Theoretical vs. Practical Range
- The APG-71 radar system is designed with the potential to detect targets at an ideal maximum range of 740 km (460 miles), under perfect conditions and with the radar’s full capability. This would be the radar’s theoretical range.
- However, in real-world operational conditions, the design of the radar’s antenna limits its performance. Specifically, the PESA (Passive Electronically Scanned Array) antenna used in the APG-71 reduces the effective range to around 230 miles (370 km) for normal operation. So, even though the radar could theoretically detect targets at 740 km, its antenna design doesn’t allow it to achieve that range on its own.
- Antenna Design Limitation
- Antenna design directly impacts the radar’s ability to send and receive signals over long distances. The APG-71’s antenna is designed for certain performance characteristics, but it’s not optimized to exploit the full theoretical range of the radar system. This design constraint means that, under normal operating conditions, it can only detect targets up to 230 miles (370 km) away, which is still impressive but less than the radar’s theoretical maximum.
- Datalinked Radar Data
- Datalinks like Link 16 allow multiple aircraft to share radar data in real-time. In the case of two F-14Ds operating together, datalinked radar data enables the aircraft to combine their radar capabilities.
- One F-14D might detect a target at the full 740 km range using its radar.
- It can then share that information with the second F-14D over the datalink.
- The second F-14D can then engage the target or continue tracking it using the data received from the first aircraft, even though its own radar might not be able to detect the target at that long range.
- Coordinated Operation Between Aircraft
- When two or more F-14Ds are linked via datalink, they effectively expand their radar coverage. They are no longer limited by the range of a single radar system. The combined radar coverage allows them to achieve the maximum theoretical range of 740 km because they are both sharing data, tracking the same target, and providing information back and forth.In other words:
- Aircraft 1 detects a target at 740 km.
- It shares this information with Aircraft 2, which can then also track and engage the target, even though Aircraft 2’s radar is limited to 370 km under normal conditions.This networked radar operation ensures that the F-14Ds can effectively operate at the radar’s full capability (740 km), even though individual radar systems are limited by their antenna designs.
The Takeaway:
- Without datalink: The APG-71 radar can typically detect targets at about 370 km (230 miles) due to its antenna design.
- With datalink: If multiple F-14Ds are operating together, they can share radar data and effectively extend their combined detection range to the radar’s theoretical 740 km (460 miles). This is possible because the aircraft can share data and track targets beyond the range of a single radar system.
In Summary:
- The APG-71 radar itself can theoretically reach 740 km, but in practice, its antenna design limits its range to 370 km.
- By using datalinks, two or more F-14Ds can share radar data and effectively combine their radar capabilities to operate as a coordinated system, allowing them to achieve the radar’s full 740 km detection range.
by chatGTP…
I think the way we think it is wrong. It’s much simpler by that explanation. I don’t know how much accurate is chatGTP though…
But it makes sense.
I think a decent way to explain it would be that this does not increased range, but “effective range”.
A radar can have a 200km instrumented range, but it can detect a 1m^2 target at let’s say 160km. In case of multiple radars working at once, there is a higher chance of detecting said target, as if one of the radars pickup it, even if it is a small signature, but it was not there, the other will also pay attention to that place, and due to for example the difference in places they are, they might pick it up. This will not double the range tho. Increase will be there, but not great.
AFAIK all that is done locally (to share small signals, you first must be able to measure them)
Again, yes, at a higher level you can share the information through datalink to improve the quality of detection by e.g. eliminating ground clutter or other false targets or blind spots more effectively.
But this doesn’t increase the absolute detection range …
(Especially not with radars next to each other … The idea in multistatic radars is to spread them out and cover the area from different angles)
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Sensors can measure below their noise floor though? it’s not generally useful outside of processing information like this, but it’s still possible. And since you can measure them you can send them. (You are correct though, for the examples I sent it is all done locally, but it could still be done from datalinked platforms assuming you had enough bandwidth.)
And this does very much increase the range, the example i sent increases maximum detection range by over 1.4x. That being said i do concede i’m not so sure of how well this would translate to a an multistatic equivalent for use as described of signal compounding, but given stuff like (the video i sent originally on camera networking), it is atleast theoretically possible, no?
Obviously above my pay grade, but I don’t see how it would be possible.
Again, sure, if you hit the area from different angles it might help with clutter rejection etc.
But two radars close to each other pointing at the same direction … I just don’t see how it would work …
If the return is so weak that it’s below the noise floor, how do you distinguish it from noise by having two radars share the information?
But AFAIK those are either done by taking the images from different angles or over time (temporal integration) or …
I don’t see how having two sensors next to each other and summing their output would give you much improvement …
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In general the more i read the more i understand that the physical limitation of the antenna doesn’t mean that it “reduces” the maximum range…more likely reduces the accuracy.
However, if one F-14D is the transmitter and the other is the receiver , the radar system’s combined gain and geometry might result in an improved effective range.
Also, you can increase the effective aperture for the receiver radar system, which improves the system’s ability to detect distant targets.
So , yes 740km is a stretch …meaning that is the theoretical maximum for a big target, with optimum parameters in favor of the F-14s, but detecting other fighters would be more like 400km …or 350km depending the conditions.
Many if not all modern planes can do that, the thing is in F-14Ds case it had big gains. especially for its era.