ALR-46 RWR - Why unable to detect launches from SA-5, SA-11, MiG-23, etc?

[Istari6]

Having learned to fly the F-4, I'm now moving into learning the weapons and defensive systems before diving into Reflected's "MiG Killers" campaign.  Just diving into the ALR-46 and how it operates, and was surprised to see the wide array of threats where the ALR-46 cannot detect a launch.

In particular, I was struck at the tables in the Heatblur manual that listed the following threats as providing no warning on launch:

* SA-5

* SA-11

* MiG-23

* F-4

Wouldn't all these systems work by SARH?  Why wouldn't a mid-1970s RWR be able to detect the CW signal of weapon guidance and alert the pilot?  It seems like fighting the MiG-23 in particular will be more challenging without knowing we've had an Apex launched at us.  

(BTW - I know that there's no warning for IR-guided systems like SA-13, that's understandable)

Edited October 16 by Istari6

[d0ppler]

At least for the MiG-23 (and MiG-21), their radar frequency is outside the bands of the RWR. Even the Viper won't see them on it's RWR. In fact I don't think any plane (in DCS) will detect them on their RWR.

[Istari6]

That's very strange.  On the inability to detect the MiG-23s CW signal, I'm 95% sure I've heard MiG-23 launch alerts when I was flying the Tomcat.  But it also seems strange that the USAF fitted RWR antennas that weren't tuned to cover the threat band of the F-4s greatest air-to-air threat in the 1970s.  I trust Heatblur has done the research and this is how the real F-4E-45MC worked.  Just trying to understand why the USAF would possibly implement such a system?  

[d0ppler]

Disregard what I said. I just saw MiG-23 on the RWR in the Viper just now.
Maybe I've dreamt, but I'm 47% sure they weren't visible couple of years back.

[Istari6]

The Viper has had a lot of Early Access issues.  My group experienced major issues with CCIP accuracy and GPS-guided weapons missing due to winds aloft.  I even logged a bug report with ED showing methodically through a controlled test how inaccurate JDAM, JSOW and WCMD were with any winds aloft.  They never replied beyond "we're looking into it", but I did notice that they listed a fix in a recent update, a year later.  So I wouldn't be surprised if the Viper just had a bugged RWR earlier.  

[Ivandrov]

On 10/16/2025 at 1:33 PM, Istari6 said:

Having learned to fly the F-4, I'm now moving into learning the weapons and defensive systems before diving into Reflected's "MiG Killers" campaign.  Just diving into the ALR-46 and how it operates, and was surprised to see the wide array of threats where the ALR-46 cannot detect a launch.

In particular, I was struck at the tables in the Heatblur manual that listed the following threats as providing no warning on launch:

* SA-5

* SA-11

* MiG-23

* F-4

Wouldn't all these systems work by SARH?  Why wouldn't a mid-1970s RWR be able to detect the CW signal of weapon guidance and alert the pilot?  It seems like fighting the MiG-23 in particular will be more challenging without knowing we've had an Apex launched at us.  

(BTW - I know that there's no warning for IR-guided systems like SA-13, that's understandable)

My understanding is that the circuitry responsible for sounding off launch warnings is specifically reserved for the guidance commands of certain C/D band SAM systems. These have very distinct signals.

 

The RWR will however sound off anytime it detects a PRF change from a present emitter. So, you'll be able to hear a MIG-23 change from search to track for instance by listening to the new guy audio tones.

 

It's an entirely different beast of RWR from anything else we've had before especially simulation wise.

 

At the time these were installed, the MIG-23 really wasn't the primary air threat, they were only in service a few years at that point, and it is unlikely that the US intelligence community at that point had the proper ELINT data to be able to feed to RWRs in the first place.

 

Also keep in mind that we're still really less than a decade (like 6 or 7 years) from when these types of RWR systems were geting fitted in these aircraft in the first place, and their primary focus in these first iterations were for SAM threats. Which is why air threats in the threat library get the short end of the stick as far as identification.

 

I guess as a TL:DR, the primary radar threat that these first RWR's were looking for was the SA-2 and the other systems employed by Vietnam. Everything else is extra.

Edited October 18 by Ivandrov

[okopanja]

SA-5: no change in signal on launch compared to tracking. At longer distance the missile seekerdoes not even point to the target. This occurs later once it turns on the target from above.

In short you can not know if this little chunk of meta attached to a much larger chunk of metal carrying large amount of explosive is traveling into your direction:

 

Edited October 18 by okopanja

[Muchocracker]

On 10/16/2025 at 12:45 PM, d0ppler said:

Even the Viper won't see them on it's RWR. In fact I don't think any plane (in DCS) will detect them on their RWR.

Demonstrably false. Sapfir's operate well within X band range. 

[Istari6]

OK thanks for the answers so far.

Sounds like there are several hypotheses:

1. Our F-4E ALR-46 might represent a mid-1970s model, which didn't have the ELINT data yet to properly convey a MiG-23 CW lock.  
2. RWRs of the ALR-46 era were focused strongly on ground threats, particularly the new SAM threat (SA-2, SA-3).  So lacking warnings for radar locks from aerial threats is typical for the period.
3. The SA-5 uses a different guidance method than the more typical SA-2 and SA-3 systems.  It seems to be a form of radio command guidance, not creating the characteristic CW tracking signal of other SAM systems.  Thus it's not detected by the ALR-46?  This is particularly weird, given that the ALR-46 seems to have been installed in B-52s, and you'd think they'd want warnings against SA-5s.  Perhaps the B-52s had other ways of detecting an SA-5 launch against them, given they were primary targets for that system?

As Ivandrov says, "It's an entirely different beast of RWR from anything else we've had before especially simulation wise".

What seems odd is that the per the Heatblur manual, our ALR-46 has a library capable of identifying and showing the following threats:

* SA-10 ("10")
* SA-11 ("11")
* SA-19 ("19")
* Patriot ("P")
* Rapier ("R")

It's also capable of detecting Launch from the following threats: 

* R-77 (MiG-29, Su-27)
* AIM-120
* SA-15 

So the library has clearly been updated at some point to represent post-1980 threats.  Anyway, thanks again for the info, helps make some sense of the unique behavior of this RWR system compared to others I've seen.  

 

[okopanja]

52 minutes ago, Istari6 said:

3. The SA-5 uses a different guidance method than the more typical SA-2 and SA-3 systems.  It seems to be a form of radio command guidance, not creating the characteristic CW tracking signal of other SAM systems.  Thus it's not detected by the ALR-46?  This is particularly weird, given that the ALR-46 seems to have been installed in B-52s, and you'd think they'd want warnings against SA-5s.  Perhaps the B-52s had other ways of detecting an SA-5 launch against them, given they were primary targets for that system?

At this stage your statement is a hypothesis. I am curious to see if you bring something fresh on this matter.

Note also that Syrian S-200 downed Israeli F-16 in 2008. Given the range of this SAM, if the RWR was giving the launch warning I would have expected that F-16 would have easily outmaneuvered the missile. Please note that very little technical information is known about this incident. Basically what was reported by IDF.

However, here is the video you can watch to learn more about S-200:

 

52 minutes ago, Istari6 said:

It's also capable of detecting Launch from the following threats: 

* R-77 (MiG-29, Su-27)
* AIM-120
* SA-15 

You do not make proper distinction here: there are 2 warnings here. One when the missile leaves the rail, the second when the missile itself becomes active with it's own radar.

In DCS launch warning is given for R-77 and is based on assumed presence of DL signal. We know this since original 29s radar has to undergo the installation of this additional channel. ED assumes that this signal is well known hence in most of the airplanes in DCS you will get launch warning even if the missile was launched from "TWS2" mode. AIM-120 does not give launch warning, it is assumed that DL updates are "silent" (no documentation available for obvious reasons), so the only indication you will have is either STT/search pass or missile becoming active on you once close enough. 

If you were worried about R-77 vs AIM-120, the later one has multiple advantages over the former in DCS.

Also SA-15 uses different kind of guidance than the other 2. 

Edited October 20 by okopanja

[Northstar98]

On 10/20/2025 at 7:41 AM, Istari6 said:

The SA-5 uses a different guidance method than the more typical SA-2 and SA-3 systems.  It seems to be a form of radio command guidance, not creating the characteristic CW tracking signal of other SAM systems.

Wrong way round. SA-2 and SA-3 use radio command guidance and don't use CW anywhere, whereas SA-5 is SARH and uses CW.

Edited October 23 by Northstar98

[Gunfreak]

On 10/17/2025 at 11:47 AM, d0ppler said:

Disregard what I said. I just saw MiG-23 on the RWR in the Viper just now.
Maybe I've dreamt, but I'm 47% sure they weren't visible couple of years back.

You see the MiG21 on rwr too, it's just so weak they are basically within visual range before they show up on the rwr.

[Czar]

On 10/17/2025 at 6:47 AM, d0ppler said:

Disregard what I said. I just saw MiG-23 on the RWR in the Viper just now.
Maybe I've dreamt, but I'm 47% sure they weren't visible couple of years back.

That percentage is an very exact number.
Nope. At least since 2022 I populated a few scenarios I made with 23s and they always showed up on all US jets RWRs, from Tomcats to Vipers.

Same goes for 21s. 

There are launch warnings from 23s in gen 4 fighters RWRs. Not from 21s, if my memory is correct.

 

[Dragon1-1]

14 hours ago, Northstar98 said:

Wrong way round. SA-2 and SA-3 use radio command guidance and don't use CW anywhere, whereas SA-5 is SARH and uses CW.

True, but here's the thing. SA-5 FCR is always in CW mode. It uses CW both for tracking and for guidance, which means you don't get a launch warning when the missile actually leaves the rail. As the Israelis found out to their detriment. 

In general, missile datalink signals should be detectable, at least by an RWR capable of listening for them. If the missile can detect the signals (it has to, otherwise command guidance wouldn't work), so can another aircraft. It's only the latest generation of missiles (AIM-120D and such) where they can't be distinguished from other datalink traffic. Hence, when you see those, you can be pretty sure that you're being launched at with a command guided missile, assuming your RWR is set up to look for them, which is a nontrivial matter. A SARH missile launch, meanwhile, is only detectable if there's a change of signal associated with it (such as a CW illuminator suddenly coming on). If the missile could guide using the same type of signal as used to get a target lock, there will be no launch warning.

Not sure why the F-4 wouldn't be able to see the CW illuminator on the MiG-23. Other F-4s, I suspect it's so that it won't be set off by its own CW illuminator, or a wingman launching a Sparrow.

[Northstar98]

9 hours ago, Dragon1-1 said:

True, but here's the thing. SA-5 FCR is always in CW mode. It uses CW both for tracking and for guidance, which means you don't get a launch warning when the missile actually leaves the rail. As the Israelis found out to their detriment. 

Yep, completely true - I'm not aware of any changes in the waveform of the 5N62 when tracking a target or when firing a missile and I even believe missiles can be guided to targets in any of its modes (either monochromatic CW, or the phase or frequency modulated modes).

Hell, I'm pretty sure its the same waveform in its acquisition modes as well (though there'll be a change in dwell time there).

The only other thing is the missile downlink (which I assume is telemetric or just to provide operators with an indication of how the intercept is proceeding/time to impact etc), but I'm not confident RWRs will be able to detect this (it would likely depend on the radiation pattern of the downlink transmitter on the missile and its power).

Rest I agree with, though looking at the manual, it seems the only SARH system that provides launch warning is the SA-6 - everything else is command guided (or at least is command-guided at launch and in the midcourse phase with the SA-10 and SA-N-6, then again, the system doesn't detect the SA-N-20 according to the manual, I'm not sure why if it can detect SA-10 and SA-N-6).

[Muchocracker]

12 hours ago, Dragon1-1 said:

In general, missile datalink signals should be detectable, at least by an RWR capable of listening for them. If the missile can detect the signals (it has to, otherwise command guidance wouldn't work), so can another aircraft. It's only the latest generation of missiles (AIM-120D and such) where they can't be distinguished from other datalink traffic. Hence, when you see those, you can be pretty sure that you're being launched at with a command guided missile, assuming your RWR is set up to look for them, which is a nontrivial matter.

This isnt as cut and dry of an answer as it is made out to be. The missile command link for amraam as an exhibit is largely a case by case basis on *how* it is transmited based on that radar system's particular operation. Hornet's APG-73 encodes them directly in its HPRF pulses presumably by phase shift keying. But the APG-68 for example does dedicated transmissions between pulses for its amraam command link because its MPRF already uses barker code phase modulation for pulse compression. You would likely not be able to detect the datalink for the former but much more likely the latter.

For other missiles and their datalinks you cant really just make blanket assumptions that they will be detectable. Everything should he individually should be studied and determine their susceptability to intercept separate from others.

 

12 hours ago, Dragon1-1 said:

A SARH missile launch, meanwhile, is only detectable if there's a change of signal associated with it (such as a CW illuminator suddenly coming on). If the missile could guide using the same type of signal as used to get a target lock, there will be no launch warning.

With PD SARH launches not all HPRF waveforms may be created equal. PDI signals are typically much higher duty cycle, more PRF stages or single adaptive PRF and no FMR in comparison to its volume search RG-HPRF. This is how the hornet's APG-73 operates at least. This isnt a factor that most people consider in the PD sparrow launch warning discourse, and i wish there was more context to the tornado foxhunter document that is commonly cited in that argument. Because it's been taken far and wide to label any system that guides SARH missiles with PDI as being undetectable launches, and the evidence just isnt there to make these kind of conclusions. 

 

3 hours ago, Northstar98 said:

Rest I agree with, though looking at the manual, it seems the only SARH system that provides launch warning is the SA-6 - everything else is command guided (or at least is command-guided at launch and in the midcourse phase with the SA-10 and SA-N-6, then again, the system doesn't detect the SA-N-20 according to the manual, I'm not sure why if it can detect SA-10 and SA-N-6).

My guess on that is because the SA-10 that's modelled is the command-SARH timeframe of that system while the 20 was well after they switched to SAGG/TVM. But i have never been able to nail down any data on how exactly TVM works on the waveform side to determine if RWR's are able to detect launches from these guidance types. Been mostly speculative. 

[Northstar98]

On 10/24/2025 at 3:22 PM, Muchocracker said:

My guess on that is because the SA-10 that's modelled is the command-SARH timeframe of that system

Well, in that case - its incorrect, all versions of the SA-10B (including the S-300PS we have and its accompanying 5V55R) are command-guided w/ terminal TVM. The SA-N-6 should fire the 5V55RM (and AFAIK has never fired the command-guided+SARH 5V55K from the S-300PT).

EDIT: Actually, no that's wrong - the 5V55K is not command-guided+terminal SARH, it's just command guided - no version of the S-300P employs SARH anywhere, only the S-300V series. The S-300P uses missiles that are either purely command-guided (S-300PT) or command-guided+terminal TVM (S-300PS/PM(U)-series and F)). 

Though the 5N63S RPN [Flap Lid-B] and the S-300PS is allegedly backwards compatible with the 5V55K, which could be further evidence that the uplink in TVM could be similar to the uplink for command-guided versions.

And while this is all speculative, why would TVM make any difference compared to command-guided and SARH? From a radar perspective, the exact same thing is happening, just what generates the steering commands is with the fire-control radar, not the missile. And for the uplink, how would it be different (if at all) between the command-guided phase and the terminal TVM phase?

Of course I have absolutely no idea about any of the waveforms the 3R41 Volna (SA-N-6), 5N63S RPN (SA-10B) or 30N6-1 [SA-N-20] produce, but right now I don't really have anything to suggest that they differ between whatever waveform is used to provide for SARH and which is used to provide TVM (at least as far as target illumination goes, of course the TVM must also include a missile uplink alongside whatever illuminating waveform).

Unfortunately apart from pontificating there's not much I can do to determine what is what, but lets say for argument's sake that from a strictly target illumination perspective, the waveform is the same and that the same waveform is used to uplink steering commands in both phases.

The way I see it (and barge of salt at the ready):

• If (and a particularly big if) the RWR can detect the uplink and determine if the aircraft is being tracked, then provided by brain ooze above is correct, then a launch warning should happen the moment the missile is launched, regardless of whether the missile is command-guided + terminal SARH or command-guided + terminal TVM.
• If the RWR can only detect when the aircraft is illuminated by whatever waveform the missile's seeker tracks (which I'm assuming is true for both TVM and SARH, there's no reason to suggest these must necessarily be different - you can use the same seeker in both set-ups, the only difference is the information from the missile's seeker gets processed and steering commands are generated locally by the missile in SARH and data linked back to the fire-control system, processed and steering commands data linked back to the missile in TVM), then you'd only get a launch warning once that starts.
• And obviously if it can detect neither then you wouldn't get a launch warning at all.

And this kind of discussion is also relevant to Patriot (which I assume is interrupted CW, given that it's supposedly transmitted from a separate array on the same radar, or at least that's what FM 44-15 implies - it describes the smaller, circular array as a "TVM array" and states that in the TVM phase a "special waveform is transmitted that illuminates the target" and then describes this waveform as "the TVM waveform" so presumably it's transmitted by this array) and the SM-2 series (which have a terminal SARH phase, though in that case the waveform is CW, somewhere in the J-band, provided by a different radar).

Edited October 26 by Northstar98

[Dragon1-1]

4 hours ago, Muchocracker said:

Because it's been taken far and wide to label any system that guides SARH missiles with PDI as being undetectable launches, and the evidence just isnt there to make these kind of conclusions. 

The question here is whether it's possible to distinguish a launch condition from a lock condition, which also incorporates a high duty cycle. Since only a single target is being tracked in STT, there's really no good reason for the waveform to change. Nobody is talking about volume search, because the Eaglejet would not be shooting Sparrows in TWS. There's usually plenty of cues for determining whether a radar is locked onto you or not, but there might be a lot less for telling apart a lock and a launch. In fact, in some Soviet designs, the CW illuminator is how the target is locked, MiG-19P for instance has two completely separate radars, one for searching and one for tracking.

The real question when designing an RWR is, whether there is any change in waveform that unambiguously indicates a weapon launch. APG-73 is pretty advanced, so its datalink is probably less interceptable, plus AIM-120 can be launched from either STT or TWS. So now we've got several problems to deal with: distingushing TWS from TWS+missile, STT from STT+missile, and TWS+missile from STT. In absence of a distinct datalink waveform, like with the APG-68, it's a tall order to provide a reliable warning here.

Incidentally, while datalink signals are a pretty definitive indicator of a launch from a fighter, it's been a well known SAM tactic in Vietnam for SA-2 crews to transmit DL signals without actually launching anything, to trick Weasels into wasting their Shrikes, or to spook whatever they're escorting. The F-4G supposedly was the only one that had a way to tell whether a launch was real or not (at least without keeping tally on the site). The big problem with launch warnings is that they're basically meant to be a "take it down right now" signal to the pilot, and thus need to be very reliable to be useful. If there is ambiguity, it might be better to put in a lock warning and rely on pilot's discretion when to start defending. It'll accomplish the same while not distracting from a possible unambiguous launch indication from another system.

Edited October 24 by Dragon1-1

[Muchocracker]

On 10/24/2025 at 11:10 AM, Northstar98 said:

Well, in that case - its incorrect, all versions of the SA-10B (including the S-300PS we have and its accompanying 5V55R) are command-guided w/ terminal TVM. The SA-N-6 should fire the 5V55RM (and AFAIK has never fired the command-guided+SARH 5V55K from the S-300PT).

EDIT: Actually, no that's wrong - the 5V55K is not command-guided+terminal SARH, it's just command guided - no version of the S-300P employs SARH anywhere, only the S-300V series. The S-300P uses missiles that are either purely command-guided (S-300PT) or command-guided+terminal TVM (S-300PS/PM(U)-series and F)). 

There's a ton of conflicting sources around that mix the P/PT and the PS/PM so it's always been hard for me to find what the truth is on the PS. The most common statements i've seen is that the 5V55R used on the PS/PM is always specified as only SARH, and not command-SARH or command-TVM. If you have more direct sources or even first party ones i'd love to add them to my collection. 
 

On 10/24/2025 at 11:10 AM, Northstar98 said:

And while this is all speculative, why would TVM make any difference compared to command-guided and SARH? From a radar perspective, the exact same thing is happening, just what generates the steering commands is with the fire-control radar, not the missile. And for the uplink, how would it be different (if at all) between the command-guided phase and the terminal TVM phase?

Using TVM affords you more flexibility in the waveforms that you can use which could or could not preclude RWR systems from keying on launches. For example again the APG-73, its PDI mode is a different CPI to CPI waveform than HPRF track and RGHPRF used in search. It's likely a single adaptive PRF and close to 50% duty cycle while only ranging based doppler frequency. Supplimented with periodic burst ranging to keep range estimation errors in line that can accumulate. Once an AIM-7 is fired it ceases all burst ranging because the sparrow has to have uninterrupted HPRF pulses to home in on. 

You don't have this limitation TVM and do more with it, you can keep your waveforms similar between track and launch without it being detectable as one by warning receivers. It also means you can do more things to hide your uplink from being detected. 
 

On 10/24/2025 at 11:10 AM, Northstar98 said:

The way I see it (and barge of salt at the ready):

• If (and a particularly big if) the RWR can detect the uplink and determine if the aircraft is being tracked, then provided by brain ooze above is correct, then a launch warning should happen the moment the missile is launched, regardless of whether the missile is command-guided + terminal SARH or command-guided + terminal TVM.
• If the RWR can only detect when the aircraft is illuminated by whatever waveform the missile's seeker tracks (which I'm assuming is true for both TVM and SARH, there's no reason to suggest these must necessarily be different - you can use the same seeker in both set-ups, the only difference is the information from the missile's seeker gets processed and steering commands are generated locally by the missile in SARH and data linked back to the fire-control system, processed and steering commands data linked back to the missile in TVM), then you'd only get a launch warning once that starts.
• And obviously if it can detect neither then you wouldn't get a launch warning at all.

Yes, if it can detect either the radar mode change or the datalink, it'll detect launch. If it cant detect either then it cant detect launch at all. The research just needs to be done on the systems in question to get specifics on how each mode operates or get specifics of the waveforms.
 

On 10/24/2025 at 11:10 AM, Northstar98 said:

And this kind of discussion is also relevant to Patriot (which I assume is interrupted CW, given that it's supposedly transmitted from a separate array on the same radar, or at least that's what FM 44-15 implies - it describes the smaller, circular array as a "TVM array" and states that in the TVM phase a "special waveform is transmitted that illuminates the target" and then describes this waveform as "the TVM waveform" so presumably it's transmitted by this array) and the SM-2 series (which have a terminal SARH phase, though in that case the waveform is CW, somewhere in the J-band, provided by a different radar).

I think you're misinterpreting things. That document does say those things, but they say it in 2 separate places not together and i think you're making conclusion to 1 based off the other. I'm not convinced the TVM array does the target illumination but instead it handles the up and down link separately so the main array doesnt have to interrupt its interlieved search/track/target illumination tasks, which is a very time-energy intesive task as it has to be continuous and be extremely rapid in update rates. The fact that the TVM array is a fraction of the size of the main array would suggest this to be the case as well. SM-2 doesn't use TVM guidance so not sure why that's being brought up, under AEGIS scheme its command-SARH while others use the 2T scheme with command/inertial-SARH. SPY tracks the interceptors for acceleration command computations and the uplink is a whole separate array task with an FSK encoded waveform. 
 

On 10/24/2025 at 1:49 PM, Dragon1-1 said:

The question here is whether it's possible to distinguish a launch condition from a lock condition, which also incorporates a high duty cycle. Since only a single target is being tracked in STT, there's really no good reason for the waveform to change. Nobody is talking about volume search, because the Eaglejet would not be shooting Sparrows in TWS. There's usually plenty of cues for determining whether a radar is locked onto you or not, but there might be a lot less for telling apart a lock and a launch. In fact, in some Soviet designs, the CW illuminator is how the target is locked, MiG-19P for instance has two completely separate radars, one for searching and one for tracking.

You missed the point i made. The search, track and PDI waveforms for the APG-73 are in fact different and there is reasons for it. It's the whole reason why i gave it as an example as to why you cant make the conclusion that PD illuminated sparrows are all undetectable launches. HPRF search is 2 PRFs with FMR and high duty cycle but lower than HPRF track, HPRF track is 4 PRFs at high duty cycle and no FMR with periodic HPRF or MRF burst ranging, HPRF PDI is single adaptive PRF to keep the target out of eclipsing zones and no burst ranging. A sufficiently modern RWR system could absolutely identify each one of these stages and trigger launch warning based on switch to PDI.
 

On 10/24/2025 at 1:49 PM, Dragon1-1 said:

The real question when designing an RWR is, whether there is any change in waveform that unambiguously indicates a weapon launch. APG-73 is pretty advanced, so its datalink is probably less interceptable, plus AIM-120 can be launched from either STT or TWS. So now we've got several problems to deal with: distingushing TWS from TWS+missile, STT from STT+missile, and TWS+missile from STT. In absence of a distinct datalink waveform, like with the APG-68, it's a tall order to provide a reliable warning here.

There is nothing advanced about a PSK/QPSK uplink to make it undetectable. The amraam's datalink is going to be constrained by the requirements of the data message format and bit encoding while having cross-compatibility across a huge variety of launch platforms all with different radars built to different requirements. There isn't any room building in LPI characteristics. Its datalink is made more or less interceptable by how that datalink is used across different platforms. The hornets is less interceptable because the encoding happens within the same HPRF pulses its sending out for target detection/tracking in any search or track mode, making whatever identified mode it is pretty much irrelevant. 

 

On 10/24/2025 at 1:49 PM, Dragon1-1 said:

It'll accomplish the same while not distracting from a possible unambiguous launch indication from another system.

This is a big point because if you design your RWR system to trigger launch warnings just on the presence of a detected datalink and nothing else, there will be a ton of false positives and the the usefulness of the system to provide adequete SA to the pilot will be very degraded. As seen by those F-4's in vietnam that had no indication of whether that datalink signal was it alone or if there was also a CW signal from the track radar. 

[Northstar98]

4 hours ago, Muchocracker said:

Using TVM affords you more flexibility in the waveforms that you can use which could or could not preclude RWR systems from keying on launches. For example again the APG-73, its PDI mode is a different CPI to CPI waveform than HPRF track and RGHPRF used in search. It's likely a single adaptive PRF and close to 50% duty cycle while only ranging based doppler frequency. Supplimented with periodic burst ranging to keep range estimation errors in line that can accumulate. Once an AIM-7 is fired it ceases all burst ranging because the sparrow has to have uninterrupted HPRF pulses to home in on. 

You don't have this limitation TVM and do more with it, you can keep your waveforms similar between track and launch without it being detectable as one by warning receivers. It also means you can do more things to hide your uplink from being detected. 

Okay, but this doesn't actually answer my question.

The point I was making is why would there necessarily be a difference between the uplink in a TVM missile vs a command-guided missile and why would an illuminating waveform necessarily be different in a SARH set up vs a TVM set up.

Yes I'm sure you can name examples where they are (APG-73 for instance, though that's fairly out of scope for a discussion mostly centred around systems that don't require continuous illumination and can simultaneously engage multiple targets), but that doesn't actually answer my question.

Essentially, what I'm asking is, is could you create a command-guided + SARH set up, using the exact same waveforms for the uplink and illumination as a command-guided + TVM set up. Especially if we're dealing with electronically scanned arrays and missiles that work with interrupted illumination (the Sparrow obviously not being one of them).

If the answer is yes, then the only thing that's relevant are what certain systems actually do, which is probably going to be harder to find. Otherwise a system merely being TVM doesn't necessarily convey that track or launch warnings should or shouldn't be detectable to a certain ELINT system (though the prevailing narrative online is that they shouldn't, often said devoid of explanation). 

4 hours ago, Muchocracker said:

I think you're misinterpreting things. That document does say those things, but they say it in 2 separate places not together and i think you're making conclusion to 1 based off the other.

Well it was an inference. A reason why is what it describes the antenna as - it uses the term "TVM antenna" instead of "uplink antenna" - Patriot missiles require an uplink during all phases of flight and it seems very odd for it to have a separate antenna for the uplink but only for the TVM phase of flight. This also circles back to my point about the uplink during command-guided flight hypothetically being no different to the TVM phase of flight and so why command-guided + SARH or command-guided + TVM or even just purely command-guided might not necessarily convey any advantages or disadvantages, assuming they can all be implemented in a similar way.

I also made the assumption that it uses 1 array for search/track/uplink and another for illumination, because as far as I can tell, that's the more common set up (even if the uplink is on a subarray), than having a wholly separate antenna for an uplink (at least for these modern radar systems) - the only one I can name is CAMM/Sea Ceptor. That's why I brought up SM-2 (though I utterly failed to elaborate on it - apologies) as that's an example as is CEAFAR-equipped ESSM-firing platforms.

These illumination antennas are also smaller than the main array, usually because they operate at shorter wavelengths, they also don't don't necessarily need to track the target themselves as the main array is already doing that. I'm not sure if that's the case with AN/MPQ-53 (as maybe the missile can use G-band illumination) in any case the size of the elements on the main array vs the TVM array appear to be same in images.

Though that's obviously not to say that there aren't systems that do combine everything under 1 radar system - APAR for instance handles all tasks, including illumination. The 5N63/30N6 series and 3R41 can handle all tasks as well (though those have a dedicated search radar, though these radars are nevertheless capable of independent search, though more limited).

Edited Tuesday at 02:00 PM by Northstar98

[Istari6]

Thanks to all for the replies on this thread.  I've read through all the responses, and it's deeply impressive how much expertise this community can bring to bear.

I'm learning a lot about the APG-73, the differences between AIM-120 and R-77, the use of TVM and the challenges of identifying specific signals (uplinks, command-guidance, etc). 

However, I'm not sure the current discussion is answering the original question about the F-4E's ALR-46 implementation.  

Let me try to phrase the original question more tightly:

-> Why can we see launches from the SA-15 and missile tracks from AIM-120 and R-77 (all modern systems), but we can't see launches from the MiG-23, F-4 or SA-11 (older systems)?

1. One hypothesis posted above is that we can't see the MiG-23 because this is a mid-1970s ALR-46 where we didn't have the ELINT data yet.  But if it's a limitation of what was known ~1975, how does our ALR-46 know the SA-15, -19, and R-77 (!)?  

2. Another hypothesis above from Ivandrov is "My understanding is that the circuitry responsible for sounding off launch warnings is specifically reserved for the guidance commands of certain C/D band SAM systems. These have very distinct signals."  This seems plausible, but if we can detect SA-6 launch, why not SA-11 launch?  Is the ALR-46 being limited to C/D bands the reason we don't pick up launches by airborne radars like MiG-23 and F-4?  

I guess I'm just confused on why the ALR-46 (as modeled for our F-4E) can detect some very modern threats that arrived well after the 1970s, yet can't detect serious threats that were present in the 1970s or early 1980s (MiG-23, SA-11).  I do understand now (thanks to this thread) why the SA-5 might be a special case and not trigger the RWR, even though older modules like F-14 and F-16 did give an SA-5 warning on launch.  

 

Edited 18 hours ago by Istari6