investigating ECM CW light behavior against SA-2.

[TEDUCK]

ECM CW light is meant to be lit when ECM detects CW illumination. In DCS it seems to be illuminated as soon as SA-2 launches missile at you.

The problem is that SA-2 has no CW mode. It uses early TWS radar (that tracks a single target while scanning), IIRC it uses FM ranging at all times and have no CW emission mode. IRL the only change when missile is launched is that RPK starts sending radio command signals to the missile and this is the marker that real RWR systems may use to trigger missile launch warning, but we are talking about ECM here and not the RWR, so that's the story for another thread

Generally speaking some doppler radar based systems may use CW mode for target illumination. SA-6 uses CW illuminator for target illumination only, it also has (monopulse?) radar for target tracking and target acquisition radar for searching. So normally SA-6 should light up both SAM and CW lights when it is guiding a missile, because ECM is detecting both CW illuminator and target tracking radar.

 

Lets go to the SA-5 scenario now. SA-5 is different kind of dog. It may use MHI mode (fancy name for CW) for both target tracking and target illumination, however it may also be guiding a missile in FKM mode (fancy therm for PM modulated ranging) and may also introduce FM mode when target is trying to hide in a notch filter. IIRC In total there are at least 4 emission modes of Square Pair radar and IIRC all 4 of them may be used for both guidance of the missile and tracking of the target.

In a typical SA-5 engagement scenario CW light would go on first, (when radar tries to establish tracking in elevation and azimuth), then SAM light would go on when radar is switched into FKM (CW light goes off) and finally CW light would go on and SAM light would extinguish (when system goes back to CW after initial ranging was established and FKM was no longer needed). Not sure if RWR would be able to classify SA-5 as SA-5 when it is in CW mode, because the only hint would be the frequency (no fancy PRF, modulation and other specific stuff that could be a fingerprint of a radar), but that is again story for another RWR thread null

Following pictures are taken from Sam Simulator manual, available on Sam Simulator author's page: https://sites.google.com/site/samsimulator1972/home

Edited November 3, 2023 by TEDUCK

[BIGNEWY]

Hi

we can mention it to the team, however we can not use another sim as a source. If you have public unclassified evidence please PM me.

thank you

[Northstar98]

11 hours ago, TEDUCK said:

Lets go to the SA-5 scenario now. SA-5 is different kind of dog. It may use MHI mode (fancy name for CW) for both target tracking and target illumination, however it may also be guiding a missile in FKM mode (fancy therm for PM modulated ranging) and may also introduce FM mode when target is trying to hide in a notch filter. IIRC In total there are at least 4 emission modes of Square Pair radar and IIRC all 4 of them may be used for both guidance of the missile and tracking of the target.

In a typical SA-5 engagement scenario CW light would go on first, (when radar tries to establish tracking in elevation and azimuth), then SAM light would go on when radar is switched into FKM (CW light goes off) and finally CW light would go on and SAM light would extinguish (when system goes back to CW after initial ranging was established and FKM was no longer needed). Not sure if RWR would be able to classify SA-5 as SA-5 when it is in CW mode, because the only hint would be the frequency (no fancy PRF, modulation and other specific stuff that could be a fingerprint of a radar), but that is again story for another RWR thread null

FWIW, all the modes described for the 5N62 are CW modes. MHI is unmodulated CW, FKM is frequency-modulated CW and there's another one which is phase-modulated CW.

All 3 modes can be utilised for missile guidance and they have their respective use-cases (for instances, unmodulated CW offers the best range, but is susceptible to losing track on targets with a low-closure rate and doesn't provide for ranging).

[Ahmed]

The OP is correct regarding the SA-2 and other non-CW waveforms in DCS wrongly illuminating the CW light. The SAM light turning off at the missile launch is also wrong.

The CW light indicates that the system has detected continuous wave illumination (@BIGNEWY refer to the FRM, among other documents, for evidence of that).

As a rule of thumb, CW illumination would normally be linked to SARH guidance. DCS seems to not distinguish between command guidance and SARH guidance for SAMs, the same way that it doesn't support different tracking/guidance methods for the different phases of the engagement. 

This is one of the many issues affecting the implementation of the DCS Hornet's ALR-67, together with the wrong implementation of the different lethality categories, missing HUD EW symbology (flashing long stem being the main miss), tones wrongly playing together, etc. Hopefully ED will pay a visit to the Hornet's RWR at some point to fix all these points.

[TEDUCK]

On 11/3/2023 at 12:59 PM, BIGNEWY said:

we can mention it to the team, however we can not use another sim as a source. If you have public unclassified evidence please PM me.

I am not using another sim as reference. I am using manual that has been written by a Sam Simulator developer who was also Sam System operator, this manual is based on real SA-5 manual (pictures are probably copied from real manual).

Regarding SA-2 I am not providing any data from other simulator, I am providing information about well known facts that command guided system with early TWS radar have no CW mode, you can also go to the SIMHQ forum where there are multiple SAM operators explaining how those systems work.

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FWIW, all the modes described for the 5N62 are CW modes. MHI is unmodulated CW, FKM is frequency-modulated CW and there's another one which is phase-modulated CW.

If it is modulated it is not called CW anymore. CW means continuous wave which doesn't change over time. If you add modulation it starts to change things like frequency, amplitude or phase over time so it is no longer continuous. Every HAM will tell you that FM, AM or PM is no longer called CW. CW is unmodulated by definition.

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All 3 modes can be utilised for missile guidance and they have their respective use-cases (for instances, unmodulated CW offers the best range, but is susceptible to losing track on targets with a low-closure rate and doesn't provide for ranging).

There are at least 4 modes of emmission:
-MHI: pure CW, best signal strength, typically used when acquiring the target or guiding the missile.
-FKM: PSK based ranging (well I have previously forgotten that this is essentially PSK and not PM), moderate reduction in signal strength.
-MHI+FM: only for small relative velocity targets, shows targets that would otherwise hide in a notch filter, may show ground clutter if antenna not in look up, some reduction in a signal strength.
-FKM+FM: almost the same as above, but with ranging possibility, biggest reduction in signal strength.

Edited November 6, 2023 by TEDUCK

[Northstar98]

On 11/4/2023 at 3:38 PM, TEDUCK said:

If it is modulated it is not called CW anymore. CW means continuous wave which doesn't change over time. If you add modulation it starts to change things like frequency, amplitude or phase over time so it is no longer continuous. Every HAM will tell you that FM, AM or PM is no longer called CW. CW is unmodulated by definition.

This is only true for simple/pure continuous wave radars.

If what you are saying was true, then FMCW radars (a kind of CW radar) wouldn't exist (such as radar altimeters) and neither would the term itself (and nor would for instance, FSK-CW). CW can absolutely be modulated while still being in the category of CW - again, see the above examples.

Even in wikipedia's continuous-wave radar page, there's a section on modulated continuous-wave, you can find webpages by HAM radio operators who talk about modulated CW as well.

Edited December 6, 2023 by Northstar98

[TEDUCK]

The article that you linked is talking about FM being used for ranging.
Square Pair radar uses PSK for ranging, and FM is only used against notching targets (to overcome the notch filter).
This is different from many radars that use FM ranging.

 

Quote

you can find webpages by HAM radio operators who talk about modulated CW as well.

In every single HAM transceiver I have ever seen CW and FM are different mutally exclusive modes. FM being used mainly for voice comms while CW can only be used for telegraphy.

Quote

Even in wikipedia's continuous-wave radar page, there's a section on modulated continuous-wave

Wikipedia page about CW is actually denying itself. First it says that:

A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency

Then it says:

Other CW radars linearly or pseudo-randomly "chirp" (frequency modulate) their transmitters rapidly enough to avoid self-interference with returns from objects beyond some minimum distance

So according to the beginning of the article it has to be fixed frequency, and according to the end of article it says it may be not... What a mess... That's why I rarely ever use Wikipedia.

Edited December 7, 2023 by TEDUCK

[Northstar98]

I think the main hang-up here is purely one of semantics - you're used to CW being referred to exclusively in the context of amateur radio, where it is understood to be a single continuous waveform of a single frequency, completely unmodulated (well, aside from on-off keying, which can be thought of as a fairly extreme form of amplitude modulation - indeed that's what's in the source used for the section of the wikipedia page you quoted).

For radars though, it is sometimes understood that a CW radar is simply one that constantly (or, put another way, continuously) transmits (i.e. not pulsed) while on the air, without interruption*. It may be unmodulated or modulated.

Maybe you're using the term more precisely and I'm using it less so.

For the F/A-18 I'm not sure whether the CW light should illuminate solely for unmodulated/pure CW (which is just about what illuminator I can think of uses for guiding SARH missiles, though as said above the 5N62 provides illumination for missile firing in all the modes listed to my knowledge).

If it is only for unmodulated/pure CW, then I can be ignored, but if it doesn't (and simply senses an uninterrupted signal) then perhaps not.

*

Spoiler

Though there is such a thing as interrupted continuous wave illumination, though that's more associated with phased-array radars like the N-007 and AN/MPQ-53).