The AIM-120 'AMRAAM' - History, Design, Performance & Discussion

Machinery of War Discussion Aircraft
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My bro has no idea what he is talking about LMFAO. You and I rarely agree on anything too.

Low PRFs without doppler are good for detection and why that is why the F-22 is claimed detected by all these countries like Venezuela and Russia lol. They are using low PRFs. However, High PRFs are required for targeting! The F22 is not hard to detect, it’s hard to track and generate a competent fire solution. It is not true stealth like the B-2 or B-21.That is why even the most advanced radar missiles AA & SA are all High PRF (interrupted continuous wave) ONLY and it is required to guide to impact. Even the R27ER must be supported by High PRF in the terminal and cannot do so alone on inertial guidance and IRST.

Because systems using PRF above 30 kHz function better for targeting because direct velocity can be measured up to 4.5 km/s but range resolution becomes more difficult by itself.

High PRF is limited to systems that require close-in performance. like radar missiles and air intercept radars. Not"head on mode The dumbest made-up terminology ever. As long as you are closing in on the target. It does not matter if are in a chase and they are flying away.

Continuous wave has **no minimum or maximum range, although the broadcast power level imposes a practical limit on range. The AWG9 should have the furthest range of all fighters when it locks a target at all aspects with the strongest field strength/broadcasting power Continuous-wave radar maximize total power on a target because the transmitter is broadcasting continuously.

When you lock a target, the radars are switching to a ** high pulse-repetition frequency**, or… aka High PRF.
The higher the PRF that is used, then the more the target is painted

The drawback of Systems using PRF above 30 kHz (High PRF) is that it becomes increasingly difficult to take multiple samples (radar return) between transmit pulses at these pulse frequencies, so range measurements are limited to short distances longer range targeting requires radars capable of emitting a combination differing PRF simultaneously to target at long ranges and having the digital processing power to interpret that and guide the missile.

Low PRF radars are the ones that have reduced sensitivity in the presence of low-velocity clutter that interfere with aircraft detection near terrain.

A radar system determines range through the time delay between pulse transmission and reception. For accurate range determination, especially over great distances a pulse must be transmitted and reflected before the next pulse is transmitted. The F14A is using low PRF to detect targets. Not while it is tracking. TWS is using a combination of both (because the jet is special like that) You cannot measure distance if you are blasting High PRF alone at targets beyond the horizon.

GJ and so many in the community have misunderstood and believed the opposite not attempting to ascertain for themselves.

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I’d like to see an 11 km frontal lock in-game at ~3 km altitude.

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As much as we argue. I always do admire your enthusiasm for the game’s future and the intentions of the corporate leadership at GJ.

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Go into a custom battle on an EC map and lock one of the F-104/Su-7s.
I even did this against a Mig-29 friend of mine when we were goofing off.

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You have shown a complete lack of understanding for how radar missiles function under various pulse repetition frequency. I think to put it simply and help you do your own (better) research… the AMRAAM (the primary discussion topic of this particular thread) goes “Pitbull” in a medium pulse repetition frequency range. This is for a reason.

Also, it seems you’re implying that SARH missiles go Pitbull here? You’re aware that the radar on the launch aircraft has to keep the target illuminated until missile impacts / detonates right? If the F-15 does so in a high PRF mode it will be limited mostly to head-on scenarios… and as far as I’m aware only early pulse doppler radars require a HPRF “lock” to get a “weapons grade track” on target. The older transmitter (CWI) was necessary and on newer aircraft they went away with this simply because the receiver of the Sparrow switched to monopulse or because the missile had it’s own active seeker and only needed mid-course inertial commands transmitted through sidelobes…

The F-14 retained a CWI, the F-15 did not. There was a study that showed how the F-15 could guide the AIM-7 via it’s high PRF radar mode without a continuous wave illumination device. This limits you to firing the Sparrow and guiding it almost solely with the “head-on” mode (High PRF) in War Thunder. That is the issue we are facing, and while I’m not up to date on my reading of the F-16C’s radar, if it lacks a continuous wave illumination device it would have a similar issue iirc.

This is how they are modeled in war thunder… yes… however it is somewhat realistic and based on reality. I suggest you do some more research into why "Continuous wave interrupted’ (High PRF 30+khz) is not normally used outside of closer ranges by stuff such as proximity fuse sensors.

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The stinger and mistral stuff is perfectly in line with their other decisions regarding the nerfing of Western ground vehicles to balance ground matches.

The AIM-9D/G was shown in the primary documentations maneuvering charts that they couldn’t really reach their maximum stated overloads under most launch conditions regarding turn radius. Stated overloads would thus only be partially capable during combined plane maneuvers iirc.

As far as the Firestreak, AIM-9G, and AIM-9L stuff… if I recall we had far less available sources on the stuff when they were first added and Gaijin spent a lot of time fixing other things. In my mind, and I imagine theirs as well… these were not very important changes that were far from the top priority. Especially as so many other changes to IR and radar guided missiles at the time were happening. I’m not sure if everyone remembers how simplistic these mechanics were at the very start.

What radars currently in the game can exercise range gating in HPRF?

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As shown to you by gunjob, the frontal lock-on range for non-afterburning targets on the AIM-9L should be reduced unless they use the standard for somewhere in the ballpark of 30 degrees off the nose.

It should be anywhere from 1.8 to 3.7km based on the chart shown, and that’s not the only one either.

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It’s not actually needed at any point, sure an AI track is nice to have but isn’t actually required.

The radar only does two things, provides the closure rate of the target in order to dynamically set the speedgate pre-launch, and point the radar array in the right direction. Both functions could be supplanted with appropriate switchology (Aspect knob) & modes (BST / manual) for the majority of airframes.

They have a thing called Flood mode, which is the equivalent of BST mode of earlier systems, and with the duty cycling target tracking could effectively interleaved between guidance pulses.

Except that the adjustment was applied when the only vehicles equipt with MANPADS were helicopters.

Technically I think the F-8’s radar counts, and the upcoming AN/APG-68(V)7 probably can.

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To follow on from that if you take the given IR boundaries I posted before, here you can see it with a supersonic target and its emissions. 35 pW/Cm² was consider a good tone on a “chirped” AIM-9L but less than 15 pW/Cm² is possible with a “de-chirped” AIM-9L.

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I believe this was a point of contention. They wanted the British to receive a de-chirped AIM-9L? Would all Li models and such be de-chirped?

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you see , 9M was much much more expensive to get , and they later found out that 9M had some problems .
so they just modified the 9L which incredibly increased its seeker range

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Low PRFs without doppler are good for detection and why that is why the F-22 is claimed detected by all these countries like Venezuela and Russia lol. They are using low PRFs. However, High PRFs are required for targeting! The F22 is not hard to detect, it’s hard to track and generate a competent fire solution. It is not true stealth like the B-2 or B-21.That is why even the most advanced radar missiles AA & SA are all High PRF (interrupted continuous wave) ONLY and it is required to guide to impact. Even the R27ER must be supported by High PRF in the terminal and cannot do so alone on inertial guidance and IRST.

You are confusing the carrier frequency and PRF. How you put it, it doesn’t nake sense. LPRF and HPRF have nothing to do with detection or targeting. Its the carrier frequency of the pulse that allows the detection of low RCS targets like the f22/b2 etc. Thats why they work in a lower frequency(VHF _ 0.03 to 0.3 GHz) compared to X band(8 to 12GHz). Its due to the Rayleigh/Mie/Scattering which amplifies the RCS depending on the target / carrier wavelength ratio. To maximize this, you gotta know perfectly choose the frequency. If you fail the normalized RCS falls. When working on low frequencies, you amplify several things, notably water drops( see why they are used as weather radars) thus you get ALOT of clutter. Though you can do doppler filtering. You can detect a target but you can’t engage it because low frequencies pulses require long pulse. With long pulses the radar resolution cell is huuuge.

When you lock a target, the radars are switching to a ** high pulse-repetition frequency**, or… aka High PRF

No, radars don’t switch to HPRF just because you want to lock a target. Most use HPRF to detect and track closing target(F4J, f15, f18, mig 29).

Continuous wave has **no minimum or maximum range, although the broadcast power level imposes a practical limit on range. The AWG9 should have the furthest range of all fighters when it locks a target at all aspects with the strongest field strength/broadcasting power Continuous-wave radar maximize total power on a target because the transmitter is broadcasting continuously

CW signals have a lower peak power than a pulsed one. Thus range more energy down range. Imagine talking without stoping for x amount of time, now imagine using all that air for a big scream for a fraction of than time. Which one will be louder?

False. The F14 uses PD for maximum detection, like the F4J and all radars. To give you proper values, in LPRF the radar detects a 5m² target at 60N.M meanwhile in RWS(or TWS) which are HPRF only have a detection of 90N.M for the rame target.

You cannot measure distance if you are blasting High PRF alone at targets beyond the horizon

You can modulate the prf to get range in HPRF. Thats how they get range gates.

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The AMRAAM (the primary discussion topic of this particular thread) goes “Pitbull” in a medium pulse repetition frequency range. This is for a reason.

Pitbull is HPRF and husky is MPRF.

If the F-15 does so in a high PRF mode it will be limited mostly to head-on scenarios… and as far as I’m aware only early pulse doppler radars require a HPRF “lock” to get a “weapons grade track” on target.

You can track a target in closure/opening/MLC.

The older transmitter (CWI) was necessary and on newer aircraft they went away with this simply because the receiver of the Sparrow switched to monopulse or because the missile had it’s own active seeker and only needed mid-course inertial commands transmitted through sidelobes…
The F-14 retained a CWI, the F-15 did not. There was a study that showed how the F-15 could guide the AIM-7 via it’s high PRF radar mode without a continuous wave illumination device. This limits you to firing the Sparrow and guiding it almost solely with the “head-on” mode (High PRF) in War Thunder

CW signal were dropped in favor of using the radar main signal as guidance because the cw illuminator had higher sidelobes, range, and digital processing of american fighters allowed better track. Why waste processing when you can guide the missile with the same signal you are tracking. Though the signal had to keep a high PRF to resemble a CW. This is because HPRF has a higher unambiguous velocity, which is needed due to a missile’s closure rate to the target.

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F14, F16 apg 66, F16C(and radar variants), surely the M20005F. Then CW signals from awg 59/awg9 are frequency modulated for range information.

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This is how they are modeled in war thunder… yes… however it is somewhat realistic and based on reality.

Modeled dishonestly would be the best description

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Pretty sure its the other way around

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It is the other way around.

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I think so, as well as the 9M. But @Flame2512 has done far more reading on this subject then myself.

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Also, is it just me, or do all IR missiles have a lower seeker range at higher altitudes? Shouldn’t it be the opposite?

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Stinger and Mistral were both originally implemented as having 18g overload. It was actively nerfed by the developers after they found a manual stating Igla was 10g. Here is a quote from the developers in response to someone reporting the Mistral in 2020:

Can you provide better reference? In the beginning all MANPAD missiles in WT (Stinger, Igla, Mistral) had ~18G lateral acceleration.

We suspected that it is wrong, but finally one user found manual for Igla MANPAD system, which claims only 10G lateral capability.

https://forum.warthunder.ru/index.php?/topic/279294-195089ne-korrektnye-ttkh-raket-9m39/

No wonder: the missile is narrow and its wings and fins are very small, no thrust-vectoring. The same for AIM-92 Stinger and Mistral.

We found datasheets with 30G, but it looks strange. We suspect that 30G is axial acceleration, not lateral. Anyway we woulbe be happy to find better reference, like the reference for Igla.

There you go. The Devs acknowledge knowing the manufacturer’s datasheet states 30g maneuverability (it is clearly written that the 30g figure refers to maneuverability not axial acceleration) but kept it at 10g because they couldn’t believe it was that much better than Igla.

Likewise my report on the Stinger this year is not the first. I just had new information become available.

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All of them, pretty much? You need range gating to establish a proper lock on a target. There is ambiguity because of HPRF but you still have a range gate. That’s then disambiguated with HF ranging techniques.