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    Su-35S vs USAF 4th and 5th gen Fighters

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    marcellogo

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    Re: Su-35S vs USAF 4th and 5th gen Fighters

    Post  marcellogo on Sun Jan 15, 2017 7:15 pm

    HM1199 wrote:ah i see , azi , and does filtering the correct signals work against all lpi methods ? for example would it work against an apg 81 sending complex waveforms and different frequencies?

    It depends from the type RWR system you use.
    They are basically radio receivers, the difference is that the older ones would look at the pulse repeating frequence; once they saw a series same radio waves incoming they knew it was a radar, alerted its presence and began to catalogate the incoming emission to know what radar it was.
    It is not that such RWR don't see the waves send by a radar in LPI mode, just as they are not repeating themselves the bell simply doesn't ring out.
    Now, actual RWR are complete ESM system: they have a way greater angular resolution, so they can ascertain the emission point of any incoming radio waves with great precision, if they sense a standard radar he previously said bell ring if a series of casual like emissions coming from a single point in space, another bell ring.

    HM1199

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    Re: Su-35S vs USAF 4th and 5th gen Fighters

    Post  HM1199 on Sun Jan 15, 2017 7:35 pm

    so basically the idea is that modern rwr's can determine from which point exactly those radio waves are coming and pinpoint the source right?
    and by extention , the R77 -1 's seeker has a second passive channel , that seeks radio emissions from a max range of 200 km , so we can say that a su 35 can position the radar of the apg 81 and fling a missile at it at a reasonable range such as 50 - 60 km for a missile kill?
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    GarryB

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    Re: Su-35S vs USAF 4th and 5th gen Fighters

    Post  GarryB on Mon Jan 16, 2017 1:15 am

    and by extention , the R77 -1 's seeker has a second passive channel , that seeks radio emissions from a max range of 200 km , so we can say that a su 35 can position the radar of the apg 81 and fling a missile at it at a reasonable range such as 50 - 60 km for a missile kill?

    No... in passive radar homing mode an R-77-1 could detect an incoming AMRAAM with its ARH seeker active and attack it, but a LPI radar spends 95% of its time listening and less than 5% emitting so a passive radar homing missile would not have a constant signal to home in on.

    Having said that NATO datalinks are L band... the same wavelength as the wing mounted radar arrays in the Su-35 and PAK FA so lots of datalink traffic would allow very long range AAMs to be used to deal with assets like AWACS and JSTARS that might be supplying data to F-22s and F-35s...


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    hoom

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    Re: Su-35S vs USAF 4th and 5th gen Fighters

    Post  hoom on Mon Jan 16, 2017 4:06 am

    Thing I can never understand is how it is possible to claim RCS in 0.0x or 0.00x m^2 range when you have something like this up the front

    AN/APG-81 is 0.7m diameter = 0.38m^2 area
    It's sloped back to deflect reflections somewhat but its nowhere near the wing sweep & all those 90deg angles on the modules must make for some excellent reflections so it seems impossible for RCS to be under say 0.3m^2 Suspect
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    Militarov

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    Re: Su-35S vs USAF 4th and 5th gen Fighters

    Post  Militarov on Mon Jan 16, 2017 4:22 am

    hoom wrote:Thing I can never understand is how it is possible to claim RCS in 0.0x or 0.00x m^2 range when you have something like this up the front

    AN/APG-81 is 0.7m diameter = 0.38m^2 area
    It's sloped back to deflect reflections somewhat but its nowhere near the wing sweep & all those 90deg angles on the modules must make for some excellent reflections so it seems impossible for RCS to be under say 0.3m^2 Suspect

    RAM coatings and materials come into whole story too.
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    hoom

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    Re: Su-35S vs USAF 4th and 5th gen Fighters

    Post  hoom on Mon Jan 16, 2017 5:15 am

    RAM coatings and materials come into whole story too.
    RAM can't cover that antenna area without crippling the radar.
    I've heard of frequency specific radome material but if that is too restrictive it must also restrict the frequency range for LPI modes & it doesn't prevent the other guys using the same frequency range -> back to something like 0.3m^2.

    Azi

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    I personally doubt F-35 can maintain a 0.001 m2 RCS

    Post  Azi on Mon Jan 16, 2017 8:35 am

    hoom wrote:
    RAM coatings and materials come into whole story too.
    RAM can't cover that antenna area without crippling the radar.
    I've heard of frequency specific radome material but if that is too restrictive it must also restrict the frequency range for LPI modes & it doesn't prevent the other guys using the same frequency range -> back to something like 0.3m^2.
    It's all about geometry!

    The correct angle, the right shape of modules in the radar...

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