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MrWolf

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Posts posted by MrWolf

  1. On 1/28/2024 at 6:06 AM, rob10 said:

    Without watching all that, realize that it will, at best, only apply to older aircraft.  The basic reason chaff is fairly ineffective with newer aircraft is that they are using doppler radars that are looking for movement and therefore can filter out the chaff (which has little movement after it is initially ejected from a moving aircraft).

    Yeah, Doppler filtering should help discard "floating chaff" from moving aircraft, very easily indeed in active missiles. For semi-active missiles it's more difficult, because the missile needs the reference signal (which for example could be taken from a backward looking antenna in the missile that gets the transmitted field by the radar antenna) in order to obtain the beating frequency and from that obtain the velocity.

    I guess chaff in modern days is similar to flares, meaning that momentarily (when it gets released) the chaff can distract the missile seeker until the speed of the chaff gets low enough to get discarded and thus the seeker points again to the aircraft.

    If the chaff cloud returns much more power than the aircraft scattering, then the chaff could mask the signal level scattered by the aircraft.

    Anyway, the point was to show that there are multiple ways to approach the SAM problem. But in DCS we have only 1.

    • Like 2
  2. Totally agree. I saw mover (real life f-18c pilot USN, has a podcast, etc.) talking about dropping bombs, and he said that even with earplugs, headset, helmet and the engine noise he could hear and feel the relief of tension when dropping bombs on the entire aircraft. Imagine dropping bombs from the wings with a +5g pull, the sudden change of tension would probably affect the wing integrity. Or even because of the g's applied the bombs could get stuck by friction to the bomb holders of the aircraft. Or the fuse wouldn't release correctly.

  3. Probably another repeated post. Probably repeating myself. The thing is that I've found some 60-70's USAF-USN training videos about radar and countermeasures. With this information available, the implementation of these features can't be flagged as "TOP-SECRET" unimplementable features. I don't want to keep it very long because videos are self-explanatory.

    Anyway, just wanted to point out that in the chaff video they say that chaff can stay quite a long time in the air, generating false returns. This is not implemented in DCS, and I think it would be a great feature, because if chaff stays in the air it can disrupt both enemies and allies for the entire sortie duration. Blinding entire map spots for 2 hours, or maybe having special notes on the mission on not dropping chaff (because of the possible interference to allies). They even mention the super top secret ECM decoy drones on 60's.... Resources are there.

     

    The long video is about ECM basic principles, systems and radar targets. Basically showing up that adding that to DCS is not "TOP-SECRET" (unknown information, or whatever). It serves as a basis of principles for more modern techniques, too.

    Chaff1:

    Chaff2:

    ECM:

     

    • Like 3
  4. Very cool DCS an beyond! MIG-29 was ovbious it has been teased for so long in previous DCS videos, sharing screen time with other full fidelity modules in most of the recent ed videos.

    I've watched Nick recent interviews and I know that DCS Dynamic Campaign is still far from release. But what about ground crew and ATC? Is DCS and beyond a hint to that? If I remember correctly the video has some yellow shirts passing command to another one.

     

    A more realistic ATC (like X-Plane, even old ones), JTACS, air commands and ground/sea crew is something that it's not as shinny as a new aircraft but IMO it's much more immersive than anything else. I mean we have all kind of navigation systems, but for what? We are currently the Kings and Queens of the game, all NPCs just vow to us when we want to do any manouver or whatever. Since the Dynamic Campaign wants to achieve a lot of things I'm not sure if ed wants to release all in one version release or progresively.

    Getting ATC and the other things before Dynamic Campaign it's also a way of keeping us entertained while the big project comes out, heheh.

     

    Well anyways, great job ed!! Until next DCS an beyond!

    • Like 7
  5. On 9/12/2022 at 12:17 AM, Ourorborus said:

    Civil Mode C (often marked ALT) is the exact same system as Military Mode 3C. And is used for ATC.

    Civil drops the "3" as they do not use Modes 1, 2, and 4. So until the advent of Mode S, all civil transponders only operated 3 and 3C. 3 (or 3A) and 3C are not different modes per say. They function identically and are compatible in all regards except for the addition of Pressure Altitude to 3C. (Note this is pressure altitude and is NOT subject to your QNH setting.)

    From an operators perspective, 1,2,3 are functionally the same, you plug in an assigned code. The interrogator asks the question and gets the code in response. THATS IT!! The term IFF is a bit misleading as it ONLY idents Friend but not Foe.

    Your 1 and 2 codes are assigned in the ATO. Your mode 3 is assigned on first contact with surveillance equipped ATC. (there also are generic codes for flight without a surveillance service).

    If the interrogator is mounted as a steerable beam on a military platform, it is usually known as IFF.

    If the interrogator has a regular sweep it is known as Secondary Surveillance RADAR (SSR).

    Just like a primary RADAR, Azimuth is gained from the direction the sensor receives the response, and distance is gained from the response time.  As Secondary (IFF) is an active response, it has a greater range for a given power. SSR is preferred over Primary Surveillance Radar (PSR) in a cooperative environment (i.e. ATC) as it is more accurate, less prone to interference and gives an ident. Also most PSR do not give an altitude, and even 3D PSR altitudes are vastly less accurate than Mode 3C.

    Mode four codes are assigned a bit more like crypto radio codes in that they are programmed into the system based on days and times etc. The Operator doesn't see the code. Mode 4 systems can also offer a little more functionality in interrogation than just the code response.

    Mode S functions the same but there are more codes in the bin and it also responds with data from the aircraft's FMS. While not actively looked at by ATC, this can trigger alerts like the pilot has dialed a different level into the FMS than ATC has cleared them.

    Thanks, this is a good summary of what i've explained on the previous messages (more detailled).

    Just 2 comments:

     

    Mode 4 only replies a set pulses at a given delay from which the interrgator can know if the target is frendly or not (this is the only information that we are sure we can trust since it's the only one comming from military source https://www.globalsecurity.org/military/library/policy/navy/nrtc/14308_ch8.pdf). No other information it's carried on the reception.

     

    Mode S really doesn't function the same as the previous ones. It's a digital design. There are no "Codes" as in the sense every aircraft tune to a given code. Digital information it's sent using Mode S. The S interrogation and replies are created by selecting fields of information and the values. This different than with the other Modes. Message are generated similar to a packaging aproach like TCP/IP.

     

    pFDo8.png.

  6. I've looked on how Deka implements IFF and it seems wrong. This is because:

    For Modes 1, 2, 3: You only need a code FOR REPLY (Deka sets codes for the interrogator too from what I understood from a youtube video, that doesn't make any sense) since interrogations doesn't contain any information of the interrogator. So you would only need to configure the transponder (the system that replies to interrogations) reply squawk codes for Modes 1, 2, 3/A. From what I've read from general aviation forums, the civilian transponders when set ON mode only reply to Mode A type interrogation, and when set to ALT it replies to Mode A and Mode C interrogations (providing squawk code and altitude, 2 interrogations needed).

     Other things to mention:

    Military aircraft should provide the same capabilities that civilian aircraft have with ON mode or ALT mode. In the case of F/A-18C DCS implementation, it shows that Mode 3 can be set to Mode 3/C (on the UFC). I guess that when the UFC shows Mode 3/C it's just plain Mode C. The ALT equivalent to military it's Mode 3 A/C: "Mode 3/C provides the aircraft's pressure altitude and is usually combined with Mode 3/A to provide a combination of a 4-digit octal code and altitude as Mode 3 A/C, often referred to as Mode A and C" (reference https://en.wikipedia.org/wiki/Aviation_transponder_interrogation_modes).

    So it seems that DCS it's pretty much simulating it! Some aspects have to be polished, as I commented here. This is great because when we get the ATC improvement we would get the possibility to use them along the ATCs. And more importantly since DCS it's also implementing Mode 3 simulation we can have a simulation working between civilian and military, simulating air intercepts, hijacks with transponder emergency transponders, military aircraft working with civilian ATCs with Mode 3 settings, etc.

  7. On 9/8/2022 at 4:07 AM, Dragon1-1 said:

    Just a note, Mode 4 is an encrypted military system which uses keys (you usually have two, A and B, this is used in case you need to be airborne at the code change time) for interrogation and response alike. Wrong interrogation code gets you no response, this was implemented because with older systems, if you interrogated them from two different directions, you could get a fairly accurate idea where the aircraft was, even if the response told you nothing about it. This could be used by the enemy for tracking the aircraft using the systems.

    Also, Mode 1 and 2 were used (I'm not sure if they still are) for mission codes and finding a specific aircraft, respectively. A mission code could be used if you wanted, for instance, quickly locate the strikers you're escorting in order to join up on them. At fence in, both of those should be turned off (and Mode 3 as well). Only Mode 4 is used in combat.

    Oh, this information is gold (thanks for this, because you made me look for the Military Modes in order to understand and explain better), now I see that my course notes that my professors gave have incorrectly nomenclature (The pulse distances are correct, but they mixed terms). SO the deal is civilian Modes follow alphabetical order, A, B, C, D..., S. Military Modes follow numerical order 1, 2, 3, 4, 5....

    Civilian use:

    Mode A: For aircraft identification.

    Mode B: For identification, it seems that it can transmit more responses (more than 4096) than A. Not sure 100%, but it makes sense.

    Mode C : For altitude interrogation. Responses have different meanings when decoded but are codified with 12 pulses as with Mode A. So they follow the same "Standard"

    Mode D : Never used. No information found

    Mode S : Stated on the previous message (long text).

     

    Military use:

    - Mode 1: For aircraft identification. The interrogation pulses are similar to the civilian ones, but shorter. The responses are codified only with 6 pulses, 2048 possible responses (2048 different identification for aircraft). Not compatible with civilian equipment. Use for identifying Mission Code.

    - Mode 2: For aircraft identification. The interrogation pulses are similar to the civilian ones, same size (4096 diferent ident.). Usually used for carrier controlled approaches during to ships during inclement weather. Use to Identify the aircraft itself, I guess it would be the tail number or some identification number inside the Carrier Strike Group (thinking of F/A-18C on carrier), because the US has more than 4096 aircraft.

    I guess that for inside friendly airspace, ATCs and other aircraft can fully identify Strike group and number plate just by asking for Mode 1 and Mode 2 ident.

    Mode 3: For aircraft identification AND altitude interrogation. Basically, this mode is "the interface" between legacy (not Mode S) civilian Modes and military. It asks and understands interrogations and messages compatible with Mode A and C standards. So you basically can use Mode 3/A and Mode 3/C in order to work with civilian airspace controllers. In DCS we can see with the F/A-18C, for example, which "submode" of Mode 3 we are using.

    unknown.png

     

    - Mode 4: For IFF (NOT ONLY AIRCRAFT), ENCRYPTED. So I was curious of how this is works, I looked into the STANAG 4193 (listed as classified https://nso.nato.int/nso/nsdd/main/list-promulg , look for 4193) and AIMS DoD (https://studylib.net/doc/7683989/dod-international-aims-program-office---dod-aims) documentation public available, not very useful. Well, one thing that's clear is that there's a communications system which transmits the Mode 4 keys to all "allowed" Military NATO operators in the world. I suppose that in legacy times these Keys were broadcasted encrypted by radio stations and bases, for oceanic keys probably VLF bands. The first time entering the "community of devices that knew the keys" you probably needed a second party already inside it providing the current keys (since key are updated), and once you are in you can update your own keys. With the introduction of GPS those keys were probably transmitted inside navigation message carried Y-code (encrypted P code), and nowadays carried inside M-Codes (GPS) which they can carry more Military information and provide other capabilities related with DataLink, MIDS, etc.

    It seems that Keys change depending on Area of Operations (Local time) and change once a day. One of these keys or some other number (code) it's used as the code to be used for the challenge.

    Well imagine you know the keys (you are "inside the key community"), then the interrogation carries an encrypted challenge. In this case, for what I've collected for different wiki and public sources, the challenge consists of a known number (shared code) encrypted. If the interrogated aircraft posses the keys, it would decrypt the interrogation message correctly and check if the received code corresponds to the current shared code between friendlies. If the decrypted code (with the known key) matches the shared code between friendlies, the receiver would send a reply, otherwise it won't. By using this technique, the receiving aircraft ensures that he isn't responding (with a reply) to an enemy which could give your position and distance if the enemy triangulated your reply by receiving it from different locations, so it's verifying the authenticity of the interrogation.

    Once the interrogation it's tested as friendly, the reply message it's created. The replay it's sent with a delay related to the encrypted challenge that the interrogator sent (so the receiver is verifying that he is friendly with this delay, see notes). The reply, it's a 3 pulse reply (I think these 3 pulses are used to correctly and precisely obtain the delay of the reply). If the interrogation receives the replay at a correct delay time, then he knows that you are friendly (from this it knows, bearing and range, and that you are friendly, as commented previously).

    It's not clear if the reply message it's a standard 12 bit data codified on pulses encrypted or just 3 pulses at the specified delay, maybe both things. The first option would explain why the DCS F/A-18 contains an A on the mode 4 (stating Mode 4/A) and it would make sense because you also would obtain ID info from the aircraft. At the same time, the second option also makes sense. In the explanation, I have chosen option 2, but option 1 seems more useful. The thing is that on Wikipedia the information stated according to option 1 has 0 references.

    NEVERMIND (FOUND ON EDIT): Mode 4 only identifies if interrogated system is friendly or not (NO IDENTIFICATION, numbers). Public military paper: https://www.globalsecurity.org/military/library/policy/navy/nrtc/14308_ch8.pdf. From this document it's worth noting :

     

    "When a transponder on another craft receives a valid interrogation, it transmits (on 1,090 MHz) a response that designates the craft as friendly and may, depending on the system, also identify the craft."

     

    also :

    "Mode 4 provides crypto-secure identification of friendlies. Mode 4 interrogations are computer-encoded pulse trains, which consist of four “sync” pulses and possibly an ISLS pulse (if it is not transmitted in the antenna’s main lobe) followed by as many as 32 information pulses. Upon receipt of a valid mode 4 interrogation, the transponder computer processes the information “word” and generates a corresponding time-encoded three-pulse reply. The interrogator subsystem, in turn, receives the reply, converts it to one pulse, and time-decodes it for presentation on the indicators."

     

    finally if there was any doubt:

    "Mode 4 is used only to verify friendly status."

     

    I may post a BUG thread, because DCS seems to implement Mode 4 as capable of transmiting Mode A (and posible Mode C too ) information. The A next to the Mode 4, means using Key A as interrogation encryption key (also implying using key B as reply encryption key).

     

    Notes: The Keys used are probably 2 long prime numbers (look to RSA cryptography if you want to know why prime numbers are important, basically prime numbers are very hard to factorize). Then the shared code, gets applied the key as exponent, creating the encrypted challenge. Then the reply delay could be constructed using the challenge encrypted (using the same technique as before) with the second key (remember there are 2 keys). This way transmitter, it's verifying that he is friendly because it's sending a shared code encrypted with one of the keys, without compromising the shared code or the key to enemies. At the same time the receiver after verifying tx is frnd, it sends a reply that verifies that he is friendly because it's transmitting the encrypted message from the interrogator encrypted (again) with the second key, without compromising the shared code of the keys.

    - Mode S: The same as for civilian aircraft.

    - Mode 5: Modernization of IFF(Not only aircraft) ENCRYPTED. It carries information digital information, using digital modulation. In this case it uses spread spectrum techniques in order to avoid spoofing, detection, etc. With Spread Spectrum, you ensure that the enemy cannot know if you are transmitting and or at which frequencies you are transmitting. This makes it difficult for the enemy to jam your signals, try to spoof it with false signals, trying to triangulate positions. Without knowing the codification applied to the spread spectrum you cannot decode the digital modulation, and because they are spread signals their signal power level may be below the noise level (or very close, if you don't know the coding) which makes it physically impossible to detect that there's even a signal being transmitted. So basically Mode 5 uses encrypted digital messaging, which allows performing more complex interrogation, transmit more data (payload info, fuel, etc.) and overall provide variable capabilities, like Mode S does, but military focused of course. The encryption it's much more complex than with Mode 4 and probably more similar to "PC encryption" tools using AES-256 or AES-512 for example. This kind of modes (Mode S or Mode 5) you have to imagine as transmitting data over your Ethernet, but using other protocols and link layer kind of designs. It also can  ADS-B GPS position (as I said, data). I think in DCS it's not modeled and all information we get of friendlies (beyond that they are friendlies) it's obtained from Data Link or MIDS (MIDS is just Data Link NATO standard in order to standardize communication between different Data Links of every country as far as I know)

     

     

    References:

    https://en.wikipedia.org/wiki/Identification_friend_or_foe

    https://en.wikipedia.org/wiki/Aviation_transponder_interrogation_modes

    http://tscm.com/iff.pdf

    https://aviation.stackexchange.com/questions/48050/what-is-mode-b-on-the-transponder

    https://military-history.fandom.com/wiki/Identification_friend_or_foe

    https://taskgroupwarrior.info/2020/iff-mode-1-and-mode-3/

    https://www.globalsecurity.org/military/systems/aircraft/systems/mark-xii.htm

    https://www.globalsecurity.org/military/library/policy/navy/nrtc/14308_ch8.pdf

     

    • Like 1
  8. 12 hours ago, Phantom711 said:

    @MrWolf

     

    My question was intentionally a bit sarcastic trying to challange those that claim, that IFF is a "radar itself".

    So for the Case 1 you are using as an example, how would the "system" know the range of that IFF reply? It wouldn`t I guess...

    As @Harker said, the range can be estimated from the response. This is because the "protocol" defines that the response start (pulse F1) has to be exactly 3 µs after the reception of the interrogation tail pulse P3. In practice, responses are transmitted 3µs +- 0.5µs tolerance (the time for processing the interrogation, detecting the interrogation).

    The interrogator would receive the response 3µs +- 0.5µs + (2*R) /c_0) ( this is the propagation delay, notice that it's accounting for the path from INTR. -> AIRCRFT and then RECV -> AIRCRFT. So R = (c*t_delay)/2. For long distances the tolerance doesn't matter much, for close distances it does. Basically by calculating the total time it took to receive the response and subtracting the predefined separation between response and interrogation you can obtain the t_delay which is physically related to the distance traveled by the EM wave (the distance at which the aircraft is present, relative to you).

     

    Also from my class notes, there are these modes:

    Mode 1: Spacing between P1 and P3 (inter. pulses) 3µs, used for Identification, Military use.

    Mode 2: Spacing between P1 and P3 (inter. pulses) 5µs, used for Identification, Military use.

    Mode 3 or A: Spacing between P1 and P3 (inter. pulses) 8µs, used for Identification, Civilian/Military use.

    Mode 4 or B: Spacing between P1 and P3 (inter. pulses) 17µs, not used (not explained why), Civilian use.

    Mode 5 or C: Spacing between P1 and P3 (inter. pulses) 21µs, used for altitude data, Civilian use.

    Mode 6 or D: Spacing between P1 and P3 (inter. pulses) 25µs, not used, Civilian use.

    Mode S or Selective (Select): It is a more complex interrogation, it is compatible with Mode A and C interrogations (which means that it can change the P1 and P3 distances accordingly), it's a flexible interrogation. It differentiates from the other interrogations because it transmits encoded digital data on the interrogation using DPSK digital modulation (it can transmit different sizes of data 56 bits or 112 bits, depending on the symbol period and constellation size...). By doing that, it's able to interrogate specific aircraft because it can indicate to whom it's sent the interrogation inside of it. The response data codification it's the same used on all the other ones (well, the response it has always the same field for all the types of interrogations, but those fields have different meanings depending on the interrogation)

     

    The response itself, it's codified by the presence or not of 12 pulses, this means 2^12 = 4096 different responses. It's a very primitive kind of digital modulation, even though it wasn't created as a digital encoding because IFF systems were created in WWII, and they didn't have digital transponders nor any ways of performing the modulations or Digital to analog conversions needed. So the response it's by nature analog, a set of 12 pulses which depending on their activations mean one message or another (with nowadays mind it can be seen as a digital encoding, but it's not intended).

     

    My course notes are a bit old, so I guess that nowadays the responses would also transmit the information using digital modulations like DPSK. And because our current digital transceivers can transmit information very fast, the embedded digital information could be introduced between original design pulse gaps without breaking compatibility with old IFF systems.

    Nowadays, IFF systems communicate information between them very similar to the way that your phone and your WIFI access point do. They use digital modulation to transmit digital data over the radio link very fast, very robust, with error correction (and detection), identification, tampering protection, etc.

     

    Mode S is like a Swiss Army solution, and it can be used for all kind of interrogations (probably military have their own, idk). This is because S mode transmits digital data both for the interrogation and the response, by doing that you can transmit ANYTHING you want because you are transmitting anything that you can encode into binary data. This makes S mode versatile. S mode is like a protocol for transmitting digital data like Ethernet IEEE 802.3, or WIFI 802.11. With S mode, you could even ask for GPS position, armament on board, aircraft systems log, etc. Mode S messages of 56 bits codify 2^56 = 7.205759404×10¹⁶ possible messages and 2^112 = 5.192296859×10³³ (notice that this isn't how it would be used because there aren't all those different messages defined, here i'm just using the representation like we did with legacy one. In reality, you send digital information separating data into headers, fields, etc. Take a look at the attached link.)

     

    You can also check, this link if you are interested.

     

    https://military-history.fandom.com/wiki/Secondary_surveillance_radar

     

    • Like 1
  9. On 6/23/2022 at 4:14 PM, toilet2000 said:

    Not at all.

    An IFF interrogator is a radar itself (called secondary radar, basically what ATCs use) and will generate contacts that can be then combined through MSI with radar contacts to generate tracks and their related HAFUs.

    As was discussed extensively before, IFF should be not only a contributor to the MSI picture, but actually a full-on sensor in itself. That's why you can steer and define IFF scan ranges on the AZ/EL page.

     

    On 6/23/2022 at 10:48 PM, Tholozor said:

    Basically yes, the bird slicers forward of the canopy are the IFF antennas for the CIT.

     

    On 6/23/2022 at 10:22 PM, Phantom711 said:

    So what you guys are saying is, that there is a second radar in the nose of a fighter aircraft, which works completely independent from the fire control radar and it not only sends out the interrogation and receives the reply (if applicable) but it also detects bearing and range of those contacts (that reply positively)? 

     

    You guys are confusing RADAR with antenna. While yes, the secondary RADAR is a different RADAR system from the primary one; because SSR transmits pulse encoded information the baseband system used for SSR it's different from a primary radar (and probably all the pass band processing is performed by the same system block that the PRI and SSR use); they both use the primary antenna. That's because SSR needs to know from which directions (which aircraft) are coming the "I'm friendly" responses (simplified).

    To do that you need an antenna with narrow beam width (well actually is more complex, the antenna has to be capable of transmitting a narrow beam for the P1 and P3 pulses of an interrogation, but also omnidirectional for the P2 pulse of interrogation, also called control. Doing so only aircraft inside the interrogation beam treat the interrogation message as for them, the rest of the aircraft treat the interrogation message as not for them). The only antenna, capable of doing that, is the same one that the PRI radar uses.

    Every slot (see radar image I attached) on the radar dish is an antenna. The use of all these small antennas, it's called an array of antennas. In order to modify the beam width, you can modify the phase of the EM waves that are transmitted or received from every small antenna, that is called phased array antenna. Doing that, you can also modify the electrical pointing of the antenna (the direction of the main lobe, simplified: the direction of the received and transmitted rays). So you could modify those phases in order to both scan the sky and also modify the beam of the array antenna. I legacy F/A-18 RADAR is PESA.

    So you may be wondering, hey PESA sounds like AESA, I know AESA. So what is the difference with PESA?

    Well the difference it's that in PESA antennas the all the antennas transmit the same signal. A better way to explaining it is that PESA antennas are "used like traditional antennas", with that i mean that once you have obtained the EM signal that you want to transmit or receive you connect it to the PESA antenna, but the system behind the antenna is the one that it's in charge of transmiting and receiving. On the other hand AESA systems use every single small antena (the slots on the RADAR dish) as a T/R system, EVERY SINGLE ONE, so basically an AESA system is a set of small antenna T/R (transmit/receive)  systems that work together and lend a result. On the other hand, PESA antennas are antennas formed up by small antennas but that are not independent.

    At the end of the day, it means that AESA antennas can achieve narrower beam width than PESA antennas ( 1/2 narrower) , but most importantly AESA antennas (because each small antenna has its own RF frontend) have lower SNR constrains for detecting returns and overall are much more robust than PESA antennas (again with AESA antennas you have hundreds of receivers, one for every small antenna, VERY EXPENSIVE). AESA antennas also have a wider frequency range. Finally with AESA antennas you can perform electronically scanning much more easier than in PESA antennas (yes with PESA antennas you can electronically scan, moving the electrical pointing), but also perform much more complex beam forming than with PESA antennas. This means that AESA antennas should be able to perform much more complex tracking and guidance of targets, even with more than one target at a time.

     

    IN CONCLUSION: If you move your Primary Radar antenna (the Antenna dish of small antennas), you are moving also your Secondary Radar antenna.

     

    Case 1: You have turned off your Primary Radar (ONLY THE BASEBAND RELATED TO PRI RADAR, without turning off any component that may affect the use of the antenna dish) and you perform a IFF interrogation INSIDE THE SCANNING AREA OF YOUR ARRAY ANTENNA, you should receive an IFF response if there's  a friendly aircraft even when you don't have a target track.

     

    Case 2: You have moved your array antenna dish (with the primary radar controls) in a way that there are no aircraft INSIDE THE SCANNING AREA OF YOUR ARRAY ANTENNA, then when you perform an IFF interrogation you SHOUDN'T RECEIVE ANY RESPONSE.

     

    On 6/22/2022 at 11:19 AM, BIGNEWY said:

    We would need a track replay to check the circumstances here and the setup of the hornet, it could easily be pilot error. 

     

    If you are on Case 2, then it's well modeled.

    Any doubts, check:

    https://en.wikipedia.org/wiki/Secondary_surveillance_radar

    https://en.wikipedia.org/wiki/Phased_array

    https://en.wikipedia.org/wiki/Passive_electronically_scanned_array

    https://en.wikipedia.org/wiki/Active_Electronically_Scanned_Array

     

    1509741548550-rtn_230611.jpg

     

     

     

     

     

     

     

     

    • Like 2
  10. FHSS it's basically used in all types of systems, most commonly Bluetooth, some 802.11 standards, and military/nontrackable comms. It's noise/interfence resistant as other SS (Spread Spectrum) techniques, like DSSS (Direct Sequence Spread Spectrum) (i.e CDMA for DSSS) etc. FHSS doesn't provide security, it just makes the frequency use random so jamming systems cannot know which band to jamm, and to overall reduce the noise/interference. But if "enemy" know your hop pattern it can listen to the comms, maybe not jam it because the speed of the hops. FHSS still requires encryption for full security.

     

    Well let's go to the point:

    FHSS uses frequency hoping along time to create an spread spectrum modulation. This means that electronic systems designed to work with this transmision scheme need to jump their carrier frequencies every x times, and because real systems aren't ideal this takes some time to perform.

    This time that the electronic systems takes to jump between carriers it's translated on abrupt periodical noise pulses that can be heard on the received signal (for example audio). As far as i know this only applies to analog (audio for example) systems; and on digital systems if the "hop time" wasn't enough symbol periods of length ( enough symbol periods regarding the codeword set used and depending on the, forward error correction mechanism, etc.) to make the codeword that was being transmitted unrecoverable, the system should be capable of recovering the data lost and make it unnoticable by a human, or even approximate what the audio sounded like (like a phone call when because of bad channel condition you can hear someone talking for a moment with a robotic voice).

    This could be a good addition to our aircraft radios: old school (or modern aircraft using old comms) aircraft having analogic comms FHSS and having this "vintage" noise over the audio.

    And modern aircraft using digital systems should have more crisp, good quality sound, when using for example MIDS.

     

    Examples for FHSS, analog, or no "hop time" recovery:

     

     

     

    Example FHSS with "hop time" recovery, notice no periodic noise (the bad quality of audio it's because the mic):

     

    Thanks 🙂

     

    • Like 1
  11. 2 hours ago, dnick said:

    Hello,

    Superlibra with f18 grip ordered in black friday arrived home in Spain in 8 days. and the extension ordered on December 26th arrived on Monday January 3rd... 8 days again... so at least to Spain they ship teh superlibra and its accesories very quickly.

    So far no delay.

    I'm from Spain. No luck with that. Vivo en Cataluña, tu?

    • Like 1
  12. Thank you all, I'm getting a bit anxious :joystick:. I'll wait until 10 days after purchase and then I'll email them if i haven't got an email yet. On their store at service part says: "If your order not shipped 10 working days after payment and no email from our company, most like your order have problem and we can not contact with you."

     

  13. Yes pleaaase can we get this fixed. I want to train without gps so i get more used to the aircraft avionics. With gps is just plug-and-play but without gps navigation becomes more fun and targeting too.

    • Like 1
  14. TACAN needs an array of antennas to perform some kind of spatial modulation that can reflect from which heading the receiving aircraft it's receiving the TACAN station signal. For distance no need of array because the distance it's obtained from the round trip time of an STATION broadcast interrogation pulse and a reply transmitted by the receiving transponder.

    https://www.globalsecurity.org/military/library/policy/navy/nrtc/14090_ch2.pdf

     

    So as someone already said: Big aircraft may be capable of having an array of antennas to perform bearing measuring (Ground stations of course) and distance, figher aircraft only capable of performing the distance measuring of the TACAN system.

    But it's dependent on the manufacturer of the aircraft maybe all those big aircraft doesn't have an array to perform TACAN bearing measuring.

     

    One thing is clear. All aircraft are capable of distance measuring with TACAN if they have a TACAN transponder and an antenna installed.

  15. On 4/5/2021 at 3:36 PM, Wdigman said:

    Does the Doppler effect change the RCS value. A HARM is probably moving faster then a GBU 12 so the SAM can see a missile better than a bomb. In 1991 we saw on CNN Patriots shooting Scud Missiles out of the sky. Fast forward to 5 or 10 years ago (not sure when) and Israel's Iron Dome can shoot down incoming mortar shells.

     

    For armor to evade bombs it would be better if the AI would know that if a jet gets within a mile or two of its position is to start moving or use smoke screens to conceal itself. Use terrain  or trees to hide vs just sitting there in the open. Laser weapons should not work if a tank or SA15 launcher moves into a wooded area or in between buildings if in an urban environment.

     

    Bet this can be done in the mission editor using triggers routs etc to hide mobile units better.

     

     

    RCS and doppler effect are completly different things.

     

    RCS is related to the effective area of an object "as it was an antenna" (but for a reflector, so it doesnt absorb power into a load, but reflects it), well or as a reflector (which can be interpreted as an antenna). The power transmited by an electromagnetic field is caraterized by a Poynting vector which on short term describes power/m^2 [W/m²]. So the RCS of an object says whats the effective area that the object has in terms of absorbing the power of an electromagnetic field. The RCS already accounts for the dielectric and other things of the material so in short the RCS tells you how many power recieved by the EM field will be radiated back.

     

    So power gets radiated through the medium losing intensity while traveling until reaches target which reflects as an RCS size ideal reflector and gets radaited back to the radar. You get squared times distance "atenuantion" (no that the field disipates on something (on air) but it gets evenly distributed on space so its intesity diminishes) and a reflection coeficient from the RCS.

     

    Doppler on the other hand (very very simplified) its related to a frequency shift on the signal that you are transmiting.

     

    RCS -> related with the power that you will recieve.

    Doppler -> related with the "shape" of the signal that you will recieve.

     

    Finally not for you:

     

    WHY THE FUCK is DCS calculating the detection of an object by RCS at ANY GIVEN DISTANCE? Is this a joke? Detection is based on power recived wich depends on a static paramter RCS and a dynamic one the "attenuation" by distance which is proportional to 1/r⁴ which is huge.

     

    As a more simple way of understanding that from this table:

    On 4/5/2021 at 3:35 PM, Tippis said:

    There are two slightly separate but related issues at play here.

     

    One is that regular bombs simply don't have the “reflection” stat that sensors (including SAM search and tracking radars) use to identify and guide weapons onto target. Bombs aren't engaged by air defences because, from their point of view, they simply don't exist. The stat that would make them show up isn't there.

     

    The other is that gliding weapons are internally defined as missiles, and those do get the reflection stat, but for whatever reason, gliding bombs are often given very tiny numbers.

     

    The JSOW has a reflection of 0.05 to 0.0618, depending on variant (this is meant to be an abstraction of effective nose-aspect RCS in m², more or less).

    The LS-6 has a reflection of 0.07.

    The GB-6  has a reflection 0.1.

    The BK-90 has a reflection of 0.4.

    The AGM-62, which could conceivably be generously included in the category, is actually just treated as a regular bomb and lacks a reflection stat.

     

    Meanwhile, the HARM has a reflection stat of 0.05 and the Maverick sits at 0.063

     

    This stat then needs to be compared against the reflection limit of the various SAMs:

    0.02 for the SA-15

    0.049 for the SA-10 and Patriot

    0.1 for the Rapier

    0.12 for the HQ-7

    0.18 for the SA-2, SA-3, SA-6, SA-11, and Roland

    0.22 for the SA-8 and Hawk

     

    …and of course, the systems then have to have low enough a scan and lock-on time to see the target before it gets too close. This is what makes the SA-15 so annoyingly good at swatting weapons out of the sky: it has the lowest reflection limit in the (DCS) business, and a good lock-on time to match. The SA-10 is set to just about be able to detect most weapons aimed at it, but it is such a small margin that it struggles, and it has to go through a series of not-entirely-brief lock-ons before it can fire a missile that is bad at engaging short-range targets. So it's quite easy to make it not even bother trying to defend itself.

     

    To “change that”, they would have to go through every bomb in the game (and there are… a few, let's say) and identify a reasonable, preferably well-sourced, RCS that can be abstracted into this internal reflection value, and then also preferably match that against reports of the system being used that way. It's not a major technical issue, but a pretty significant research, balance, and testing one.

     

    An SA-15 in DCS can detect an object with RCS of 0.02 so an ideal square reflector of 14,14 cm by 14,14 cm at any distance (because DCS detecion is based on RCS (WTF)). So a 14,14cm by 14,14cm reflector 10.000.000.000.000 km away from the radar can be detected by SA-15 DCS (hahahhaha). Or the same thing as saying that if you put the same square reflector infront of the antena of an SA-8 it won't be detected because i has an RCS lower than the detected by a SA-8 (imagine literaly blocking all the aperture of a horn antena and not detecing it because RCS lower than RCS of radar?¿?¿?)

    Well i hope this information isn't correct because it's a very bad implementation of a radar and probably a lots of bugs come from this.

     

    For you guys to understand: for a given RADAR with certain parameters, reducing the RCS of an object that we want to detect reduces the range at which will be detected. But reducing RCS doesn't make you invisible like some kind magic.

    RCS it's like what size a visbile object has. You can see a fly if it's close to you, but if the fly is 5-10m away you won't be able to see it, say you cannot diferenciate it from the background.

    In RADAR is the same but the term "differenciate from background" it's related with having a recieved power of an object higher than the noise level of the system. Which is related (just like with our vision) with the distance of the object to your radar and the size of the object (the RCS).

     

    RCS is related to the material on which is reflecting the EM wave and MOST important the angle of incidence. If you notice stealth aircraft don't have angles of 90º from any prespective (well mostly from the side because aircrafts get radiated from the sides not from directly below).

    Tail Wings straight up like F15 super bad (high RCS from sides), that's why f18 has tail tilted and why f22-f35-f117 too. Probably f16 has worse RCS than f18 (just guessing by it's tail).  Spcherical or cilindrical shapes worse than right angles, you get bad RCS from ALL directions, so A-10 motors are horribly bad on terms of RCS.

     

    Then other factors that affect detection is doppler shift but this on terms on "signal processing". With doppler you can reduce your SNR needed to detect an object because you can discriminate from you transmited signal and the recieved one that something modified your pulse that you sent, so there is something there (VERY SIMPLIFIED).

    Engines generate Very high dopler signatures !VERY HIGH!. So that's why also stealth aircraft have engine intakes on top of the aircraft and not below them (radar mostly look at them from a lateral below them).  F18 tries to hide its turbine blades from outside by doing some kind of curved intake. F16 something similar. A10 super bad turbine blades visible, spherical motors... . F117 turbine intakes on top and with bars to hide blades. etc...

    Also take a look at JSOW its strange shape is to not have right angles (90º), well actually the RCS has to be reduced on front mostly its like and V shape but with diferent slopes:isra-tan-agm-154c-002.jpg?1582658371

     

    Compare it to a TALD decoy (that you want to get detected). Right angles, probably made of a metal good reflector. :

    itald1.jpg?itok=W7FVRVdU

     

     

    Dumb bombs are cilindrical like so bad RCS but normally you only see the front so RCS not so big. Same applies for rockets (clindrical like). So as i said maybe when the radar detects the bomb it will be too late. But the RADAR WILL DETECT AT SOME MOMENT THE BOMB.

     

     

     

    • Like 3
  16. 4 hours ago, Hulkbust44 said:

    SRS already takes care of most of the voice systems. Even MIDS and KY-58 to some extent. We would need a native DCS global radio system to rival SRS in the near future.

    Mobius708
     

     

    SRS-DCS doesn't achieve anything i mentioned and i don't think that will ever achieve it. As far as I know SRS only uses plain single channel radio links for AM and FM radios. He treats BOTH FM and AM as the same, i mean as it is implemented radio volume gets lower the far you are from the emitter, which makes some sense for AM and not so much for FM (as in FM the voice isn't modulated as amplitude so the attenuation when propagating shouldn't affect as in AM, where directly attenuating the radio signal means attenuating the voice amplitude).

     

    It isn't simulating MIDS. MIDS as far as I understand for what stands for is a military network. Meaning talking over MIDS means converting your voice transmitting it through this link as a set of bits. So no SRS doesn't simulate MIDS because MIDS is a military network not only used to send voice but any data (targets, waypoints, AWACS calls, monitor targets, etc).

     

    https://www.usna.edu/COVID-19/Remote/MIDS.php

     

    So SRS only simulates and very simpler, without any frequency switching or SS, classical AM and FM radios used ONLY for voice.

     

    Just to make things clear KY-58 it's an analogical cipher. It's only used with FM and AM because that type of modulations re-transmit your analogical voice. 

     

    MIDS cipher it isn't made by the KY-58. Some digital algorithm encrypts data sent through the network link. Imagine MIDS as if your PC  with WIFI was an aircraft connecting to a private network made by other PCs (aircraft, soliders pda, command control offices, etc), that's MIDS. And you send digital packets to other members of that network with your PC (aircraft), which could be audio, targets, etc.

     

    The guy doing SRS is doing just an app to connect via VoiceIP guys playing DCS on the same server, but a bit fancy. That means that you can interactuate with this VoiceIP app (like discord for example) with your DCS buttons on the aircraft. For example (simplification) changing your AM frequency changes your APP (think like discord) voice channel to a new one.

     

    3 hours ago, Swiftwin9s said:

    What we need is for ED to implement all of the comm submenus, even if all of the actions are non functional. SRS will take up the slack.

    SRS cannot create the other things (like all the stuff i talked about) it would have to duplicate all the iternal network that DCS aircraft and subsystems have to implement it. SRS it's just a VoiceIP APP like discord or TS. Not a militar telecomuncations network simulator, which it's needed to have some real life coherence with regard ECM, JAMMING, ECCM, Chiper, IFF interrogation, etc etc etc.

     

    The implementation has to be internal, because all the aircraft systems are actually tied to this things. That's why i don't understand it isn't implemented

  17. Yesterday i was reading through the COMM-NAV systems described on "NATOPS FLIGHT MANUAL NAVY MODEL F/A-18A/B/C/D161353 AND UP AIRCRAFT" and i noticed that all practical and not technical details of this technologies are well explained and enumerated.

     

    Knowing that, why we still have an Arma3 like systems when the documentation is there?

     

    If DCS stands for Digital Combat Simulator then it should simulate the most important aspect on today combats: Telecommunication Systems.

     

    No source available? Not true. You don't need to simulate the mechanisms exactly as the USN does or whatever. DCS could have a general API for all this systems. You don't even need to calculate wave propagation. Use simple propagation equations to calculate the power density of signals. Frequency switching you can program it as a simple channel switching (say you divide the spectrum in fixed frequency lengths which you number as channels and treat it as 1-2-3-etc), for the "enemy" trying to jam or intercept the signals that is getting frequency switched you can simulate a channel scanning searching for certain power level threshold (so every x seconds this algorithms checks the channel n for a power level above whatever threshold, the channel scanning can be sequential or variable). Spread Spectrum techniques can be simulated as a low power signal distributed a long many frequency channels, for "allies" that know the pseudo-random sequences used to spread the signal (im talking about DSSS) can obtain the signal easily, for the "enemies" that don't know the sequence cannot distinguish noise level from the actual signal (at long ranges from the sender and enemy listener). At closer distances or very well calibrated and sensitive enemy jammers you could use a high number of spread spectrum bands (i.e 4 spread spectrum bands that fill 5 frequency channels each) you could create a SS (Spread spectrum) channels that all transmit the same information. The jammer could jam one of the SS channels and the ally receivers only read the channels that aren't getting jammed (rake receiver).

     

     

    There's also more techniques some based on the fact that the ally systems are all synchronized on a global time reference and can send information on certain time slots or with certain time characteristics.

     

    If we already know that this techniques are on the aircraft and the details on how to select and use each of these techniques are open to the public, what prevents you from modeling it?

     

    If it's for the technical and physical implementation don't worry about. You don't need to simulate the bits per second that a system is receiving regarding the fading of signals, doppler effect on telecom signals, multi-path reflections, directivity of antennas, electrical noise, interference between other telecom systems, etc etc. You can divide the frequency band on channels, use simple calculations of power density and propagation, use SNR (jamming signals are considered noise) levels to know if that telecom link is good ( no errors in the signal no degradation), medium (some degradation), bad (very high degradation, lose of link).

     

    For SS the jamming system would have to jam all the SS spectrum with A LOT of power (which means that the jamming system first has detected the SS that wants to jam) to transform the link into bad state.

     

    For SS with rake receiver the jamming system would have to jam all the SS channels involved with A LOT of power (very unlikely) to bring the link to bad condition.

     

    For frequency switching the jamming system would have to identify the switching pattern that the aircraft is using and timming to jam the link correctly. Most of the frequency switching use a pseudo-random generator that is feed a seed number which generates a deterministic sequence (that feeds it self) of a very high length. This sequence seen as an outsider looks as if it was a random sequence (if the outsider doesn't know the seed). With this random sequence the two communicating systems can perform a know frequency switching for them, but a random switching for external viewers. This way the enemy cannot induce a deterministic sequence from listening and detecting the frecuency switching.

     

    Above all of this with the use of the KY-58 to cipher the voice that is going to be transmitted through this links. For the Ky-58 you don't need to simulate anything only if the voice is encrypted or not.

     

    The capability of the aircraft to act as relay would be also important. This way aircrafts can form an internal net between them without the need of external systems (i.e satellites, ground systems, AWACS, Air control, etc). Also if aircraft act as a relay between close squadrons they can transmit lower power signals which are more difficult to detect by the enemy (which could mean enemy not jamming that signal).

     

    A lot of Anti-Jamming techniques use the links between other aircraft to communicate and transmit information data even in very high jamming conditions. Because the aircraft form a low range links between them which are very difficult to jam (require massive power, not possible) and eventually one of the aircraft nodes that has a link with the global network can transmit all the information of aircraft net. This techniques are also used in satellites for example, that are designed forming a constellation where all the satellites act as nodes and re-transmit information between them when some of the satellites has direct link connection with ground bases.

     

     

    Some of the navigation systems are also capable of being transmitted through this links making TACAN and GPS navigation even in jamming environments.

     

     

    I only covered the simple stuff, in the Manual I'm mentioning there's a lot of things that we don't have yet. Regarding GPS alignment, TACAN navigation and secure communication techniques that you can select on the aircraft.

     

    I hope this brings light to aspects that need to be polished and/or worked on if you want to achieve a simulation. And regarding the jamming techniques, SS, etc. I just wanted to make you know that it's not that difficult to simulate it and that IMO it should be simulated as is the basis for aircraft that we have and yet are to come.

     

     

     

    Probably this post will moved to whatever place and unseen, just as the last post where i pointed out that FCS system isn't well simulated acording to this Manual.

     

    Well Anyways, Thank you for taking your time to read this :).

    • Thanks 1
  18. 2 hours ago, ruddy122 said:

    I still suck at Carrier Landings

    For me trim doesn’t help it makes the Hornet worse on landing

    I PIO in roll a lot on landing

    Also the extremely slow response of the F404

    I know engines may take up to three seconds to spool up but the response of the 404 concerns me


    Sent from my iPhone using Tapatalk

     

    Carrier landings are fine for me just trim the E and dont touch it more along the recovery. Its all about throtlle control.

     

    I just posted this because i want the virtual aircraft to simulate as accurate as posible the real one.

     

    Seeing some key aspects are still not being fixed in almost hornet release is concerning.

  19. As the title says i wanted to point out some features that aren't implemented in comparison to the real aircraft. So in FCS an FCS BIT related stuff i have found a lot of problems when o try to follow the NATOPS manual to start my plane. Most of these problems are related to FCS and FCS BIT. Luckly i found bug posts from 2018 that already stated this problems. The thing is that this posts are totally forgoten by devs, which in my opinion is bad because we are talking about a main feature of the aircraft the FCS and not a fancy weapon which its operation time doesnt match with our hornet.

     

    Please devs take a look at this bug post https://forums.eagle.ru/topic/180980-fcs-reset-with-wings-folded/?tab=comments#comment-181007 and fix the remaining issues with this system. Having FCS modeled correct it's important if you want to release the hornet as a finished product. 

     

    Thanks

    • Like 3
    • Thanks 1
  20. On 4/22/2021 at 6:05 PM, StevanJ said:


    If you can record it, and prove he's flying at the wrong speed in a track, you can report it as a bug.
    Try doing it again, and showing us his stats in a replay using F2 view on him.

    Youll also get some help from others on here who have better experience with the AI, I only play online, and the Dora is the 'air-king' for speed.

    Since amazingame posted a dogfight with him wining vs spit, i think the problem is solved. Now i just have to get better.

    • Like 3
  21. On 4/22/2021 at 6:05 PM, amazingme said:

    Here's how it should look against that puppy, freshly made:

    https://youtu.be/Or-BI51RH28

     

     

    WOW amazing, so i can be done, thank you soo much now i have confidence in trying vertical fights until i master this fight, i didnt try this type of engagement because i thought it was useless, but i was wrong, thank you.

     

    Also what are you DCS and gpu settings, because with my settings is very dificult to spot planes. It maybe the aliasing because planes mimetize with the ground or sky becoming invisible.

     

    I play at 2k, a spotting/high visbility focused settings would be much apreciated if you share it with me 🙂

     

    Thanks a lot

    • Like 1
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