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kimjongnumbaun

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Unread post07 Aug 2018, 23:03

playloud wrote:
steve2267 wrote:Am guessing that the lower end -- 2.0GHz -- is still quite a bit above "low frequency" search dars?

Who knows how the technology has advanced. That patent is 30 years old.
radars.jpg


S-band is used for acquisition radars, so still above search radars which operate in L-band.
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Unread post08 Aug 2018, 09:22

michaelemouse wrote:
hornetfinn wrote:Very true. Besides if I read this correctly, then there are rather narrow spikes even in lower than UHF frequencies. This would mean those radars would likely only see fairly infrequent detections (radar plots) and maybe rather sporadic tracks. This is because low frequency radars usually need quite a few plots to generate track as otherwise they'd have a lot of false target tracks. AESA technology will help somewhat, but the effect is still there.

Not to claim that low frequencies are useless or not a threat (especially for a manned cruise missile like F-117). However low frequency radars are hardly the silver bullet some people claim or wish for.


Is the relationship between the frequency and the number of plots required for a track linear? I.e.: If you decrease frequency by half, you need about twice as many plots for a track?


No, it's not that linear but lower the frequency and longer the range, then the tracking becomes more difficult because of very large number of detections (plots) generated by clutter (like ground, sea, rain, EW, chaff). Another thing that affects is the low resolution of low band radars. So the errors and uncertainty are far larger in each individual detections and thus higher number of plots are needed for reliable track initiation and confirmation. Usually X-band radars can initiate tracking from only 2-3 consecutive detections (plots). L-band surveillance radars tend to need 5-10 consecutive plots for reliable track initiation. It could be done with lower number of consecutive plots, but then false tracks from clutter become serious problem. Even with higher number of plots, there tend to be false tracks especially in older systems with less capable signal processing and filtering.

michaelemouse wrote:From what I understand, while absence of detectability or absence of track are desired, stealth is mainly about decreasing the range or probability of attaining a sufficiently timely and precise targeting solution. I presume the range cell resolution is usually precise enough but the azimuth/elevation cells might be much larger than the effective damage area of a warhead. Even with a precise-enough targeting solution, you need to update it often enough if the target takes evasive maneuvers, otherwise it's like playing an online first-person shooter with a 5FPS framerate. Add to that that a stealth strike aircraft would likely be supported by EW to generate even more false tracks and survivability might be much increased.

How would a system trying to take down an F-117 or similar go about distinguishing between true target tracks, false target tracks from jamming and false target tracks from unintentional noise?


That's true. The real F-117 shootdown in 1999 shows one good example. P-18 radar operating in VHF frequencies managed to detect F-117 first at about 50-60 km out according to serbian operators and got stable plots from 25 km away. There is no automatic tracker in that version of P-18, so this is basically where they were tracking (by hand) the F-117. As the detection range for 2.5 square meter target is >= 175 km with this radar according to some specs I could find (about their upgrades), it's clear that even F-117 stealth features really are effective even against VHF radars. They may not be as effective as in higher frequencies, but still effective.
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Unread post08 Aug 2018, 15:16

So the RCS of the F-117 in VHF mode is about 0.03 sq m which is in the ballpark of the general numbers claimed for F-117 with the numbers generally smaller in X-band. The continual Russian claim that US low stealth numbers are grossly exaggerated don't seem to hold up
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Unread post09 Aug 2018, 06:49

marsavian wrote:So the RCS of the F-117 in VHF mode is about 0.03 sq m which is in the ballpark of the general numbers claimed for F-117 with the numbers generally smaller in X-band. The continual Russian claim that US low stealth numbers are grossly exaggerated don't seem to hold up


Real world detection ranges vary depending on all kinds of reasons (operating environment, weather, other interferences). AFAIK, the weather then was not great but there also was no EW support in the area. Also those ranges in specs are usually when the radar itself detects the target (first hit) but that's usually somewhat before operator (or computer) realizes that there actually is a target there. That requires at least some fairly consecutive detections. However the difference is not that big and I'd say that that ballpark could well be correct. It might be somewhat bigger (like 0.1 sq m) but that's really difficult to say using only one real world engagement. In any case it's very clear that F-117 stealth features make it much harder to detect even in VHF frequencies. Besides it would not matter much if stealth aircraft were easily seen in VHF frequencies as the enemy would still have very hard time successfully engaging those stealth aircraft with any weapons system.
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eloise

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Unread post10 Aug 2018, 05:20

Book written by Serbia SAM crews who shot down F-117:
Suddenly on the observation radar, I see the target on azimuth 195, 23 kilometers away. The next circle on the observation radar clearly indicates that the plane is approaching us. I say: "Dani, this is going to us!" Days opened his eyes, looked at the screen, and uninterestedly followed the situation. The reflection approached us. The plane was at 14-15 km, when Dani ordered: "Azimuth 210, search!" As an assistant to the shooting man, I ordered that moment: "Antenna!" The commander of the battery began to point the guiding officer on the azimuth and the meat corner to the target - left, left: stop !, right, up, up: stop! - antenna. He switched on the radiation of the observation radar. That's when the cats and the mouse started playing. Who will be faster and more skilful. The guiding officer, turning three wheels at the same time, tries to find the target. We run for more than ten seconds in an unsuccessful search for the target. Ordering: "Stop Searching - Equivalent!" After a few moments, Dani again orders the new search azimuth 230, and I am the moment of radiation. Adrenaline is in the air. This road manager manages to see the target on his two screens, but in no way can he cover it with a cross-section of horizontal and vertical markers. The dots just shrink - it has to push them out, cover the goal in the cross-section of the two markers. At the moment when the target is in the cross-section of the marker, they can begin to be monitored by manual tracking operators - by plane F1 and F2 on their pointers. Then conditions were created for the guidance officer to monitor the goal by distance, and manual tracking operators to run launched missiles at the target that is in the cross-section of the marker. The goal is to run and maneuver. Again the radiation time is too long and I order: "Stop searching - equivalent!" After a few seconds, we try the same procedure, the third time on the azimuth 240. Very soon, after a few seconds, the guidance officer finds the target and reports that the goal is to maneuver. The dashboards of the guards are shaking, the operators are losing it. The radiation time was long and dark when I wanted to order: "Stop searching - equivalent", the monitor of the monitor, Dragan Matić, cried out, "Give it! Give it, I have it!"



He energically turned his wheel, trying to bring the reflection from the target to the center of the screen. He succeeded. The tracking operators managed to hit the target with a cross - cross-section of two markers and thus provide the conditions for launching the missile. Another tracking operator, Dejan Tiosavljević, reports that the goal is to have a large reflecting surface. That moment, I say to Daniel: "Take care that it's not bait to screw us." My thoughts on war experiences from Iraq passed through my mind when the united forces put up angular reflectors on unmanned aircraft and thereby increased the reflective surface. The Iraqi combat crew thought it was a real plane and began radiating a Nishan radar. At that moment, airborne hunters captured the radar-nišan location and then eliminated the missile from anti-aircraft missiles from the ambush. The guiding officer, Muminović, reports - the station follows the target, the target on arrival, a distance of 13 kilometers. At the same time, operators report - by F1 I follow the target, following F2 I follow the goal. Dani commanded: "Object Destroy, Method T / T Launch!"


According to the book, P-15 (operate in UHF band) detected F-117 from 23 km, SNR-125 (operate in X-band) detected F-117 at distance less than 14 km.
P-15 claimed to have range = 150 km, assumming this is detection range is against target with RCS = 10 m2, this radar will detect target will RCS of -30 dBsm (0.001m2) from 14 km and it will detect target with RCS = -20dBsm (0.01m2) from 26 km, P-15 detect the F-117 from 23 km, therfore in UHF band -20 dBsm > F-117 RCS > -30 dBsm

X-band radar.PNG

SNR-125 can detect target with RCS = 10m2 from 80 nm (148 km), according to radar equation, 10 times reduction in RCS will decrease detection range down to 56%, so a target with RCS = 0.001 m2 will be detected at 7.87 nm (or 14.5 km), F-117 was tracked and detect at distance less than 14 km so F-117 rcs in X-band is less than 0.001m2.
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hythelday

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Unread post10 Aug 2018, 06:30

eloise wrote:Book written by Serbia SAM crews who shot down F-117:....


What is this book called exactly? The quote you have given seems to be a mediocre translation.
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Unread post10 Aug 2018, 08:02

hythelday wrote:What is this book called exactly? The quote you have given seems to be a mediocre translation.

Here
http://www.lektire.me/prepricano/djordj ... -smena_945
I used google translate so it isn't very good.
There is this one as well
https://www.kurir.rs/vesti/drustvo/3027 ... bio-oboren
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Unread post10 Aug 2018, 09:49

eloise wrote:Book written by Serbia SAM crews who shot down F-117:
Suddenly on the observation radar, I see the target on azimuth 195, 23 kilometers away. The next circle on the observation radar clearly indicates that the plane is approaching us. I say: "Dani, this is going to us!" Days opened his eyes, looked at the screen, and uninterestedly followed the situation. The reflection approached us. The plane was at 14-15 km, when Dani ordered: "Azimuth 210, search!"


According to the book, P-15 (operate in UHF band) detected F-117 from 23 km, SNR-125 (operate in X-band) detected F-117 at distance less than 14 km.
P-15 claimed to have range = 150 km, assumming this is detection range is against target with RCS = 10 m2, this radar will detect target will RCS of -30 dBsm (0.001m2) from 14 km and it will detect target with RCS = -20dBsm (0.01m2) from 26 km, P-15 detect the F-117 from 23 km, therfore in UHF band -20 dBsm > F-117 RCS > -30 dBsm


There seems to be confusion in terminology here:

When radar system first detects something (gets radar return that crosses threshold values), nobody actually knows there is a target there. It might be just clutter echo or some anomaly in the system. Usually there needs to be at least 2 detections (preferably more, especially in lower frequency surveillance systems) before anybody (operator or computer) has an idea that they have actually detected a target. The radar detection range used in specs and equations is the range where they get the first radar return at some predetermined probability. Many specs published about older Soviet equipment use 50 percent probability which is still useless range in real world as it will generate far too many radar returns and false targets. This is why modern systems usually use 80 to 90 percent probability as that's more realistic value.

Basically there are three different ranges:
1. Radar system detection range. This is where radar receiver gets a target return that crosses detection threshold values. This is pretty theoretical range especially with low probability values as those would overwhelm the receiver and processing system (computer or operator in older radars).

2. Operator/automatic tracker detection range. This is the range where operator or automatic tracker realizes that they have actually detected a target. This is range where tracking process is started to actually track the target.

3. Tracking range where target is being actually tracked with enough information to commence engagement for example.

The 23 km range in that Serbian book seems to be the second range. They needed some more returns to be sure and so actual target tracking was commenced somewhat closer (about 18 km away). The first range could be significantly longer range but it could only be estimated reviewing radar video of that engagement. Maybe that's where the 50-60 km range in some quotes comes from.

It also seems that there is some confusion if it was actually P-18 or P-15 system that first detected the F-117. P-15 has 140 km detection range against 2.5 square meter target (with low 50 percent probability) and uses UHF frequencies. P-18 has somewhat longer detection range (175-250 km depending on mounting) using same criterias and uses lower VHF frequencies. In any case it's very clear that F-117 stealth features give it huge advantage even against low frequency radars. Regular fighter would've been detected at 3-4 times longer ranges for sure given the same circumstances.
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Unread post10 Aug 2018, 11:36

hornetfinn wrote:The 23 km range in that Serbian book seems to be the second range. They needed some more returns to be sure and so actual target tracking was commenced somewhat closer (about 18 km away). The first range could be significantly longer range but it could only be estimated reviewing radar video of that engagement. Maybe that's where the 50-60 km range in some quotes comes from.

It also seems that there is some confusion if it was actually P-18 or P-15 system that first detected the F-117. P-15 has 140 km detection range against 2.5 square meter target (with low 50 percent probability) and uses UHF frequencies. P-18 has somewhat longer detection range (175-250 km depending on mounting) using same criterias and uses lower VHF frequencies. In any case it's very clear that F-117 stealth features give it huge advantage even against low frequency radars. Regular fighter would've been detected at 3-4 times longer ranges for sure given the same circumstances.

Apparently, the author of the book Djordje Anicic is the crew of P-15 radar and they detect F-117 from 23 km
Capture.PNG


whereas zoltan dani is in P-18 cabin??
https://www.kurir.rs/vesti/drustvo/3027 ... bio-oboren
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Unread post10 Aug 2018, 12:16

Thanks eloise. So it seems like they had both P-15 radar and also P-18 radar. That picture seems to indicate that the P-15 belonged to the battery and the battery also got support or had the P-18 system attached directly. Interesting to read about this from Serbian POV. It seems like they knew very well what they were doing and executed very well with such ancient equipment. They also had a lot of luck in that they didn't have to deal with jamming or HARMs in that engagement and that F-117 flew well into engagement envelope. Even then it was clearly not an easy engagement. This engagement showed that F-117 VLO stealth work very well even in VHF/UHF frequencies. It also showed that ancient equipment can still be very dangerous with very skilled operators. Of course F-117 is very archaic besides the VLO stealth features (not much sensors to speak of, low flight performance).
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Unread post10 Aug 2018, 14:23

hornetfinn wrote:Basically there are three different ranges:
1. Radar system detection range. This is where radar receiver gets a target return that crosses detection threshold values. This is pretty theoretical range especially with low probability values as those would overwhelm the receiver and processing system (computer or operator in older radars).


Is this % calculated per pulse? If so, wouldn't sending 100s of pulses and using time integration get rid of the false returns pretty quickly? You might need 10 plots to get a track but if each pulse you send out has a 50% of crossing the threshold value and you send 10 000 of them per second, it shouldn't take much time to get a track. Maybe I'm missing something.


hornetfinn wrote:Thanks eloise. So it seems like they had both P-15 radar and also P-18 radar. That picture seems to indicate that the P-15 belonged to the battery and the battery also got support or had the P-18 system attached directly. Interesting to read about this from Serbian POV. It seems like they knew very well what they were doing and executed very well with such ancient equipment.)


I've wondered if they had some significant help. If I'd been Russia or China during the NATO bombing of Yoguslavia, I would have been very interested in exchanging information with the Serbs to know what it's like to face NATO air/naval assets & tactics. The F-117 was shot on March 27th and on May 7th, the Chinese embassy was bombed in what the US said a map/intel failure. I don't know enough to be sure but it might have been the equivalent of "accidentally" dropping a cup of coffee on someone you want to butt out of a conversation.
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Unread post11 Aug 2018, 04:32

hornetfinn wrote:
eloise wrote:Book written by Serbia SAM crews who shot down F-117:
Suddenly on the observation radar, I see the target on azimuth 195, 23 kilometers away. The next circle on the observation radar clearly indicates that the plane is approaching us. I say: "Dani, this is going to us!" Days opened his eyes, looked at the screen, and uninterestedly followed the situation. The reflection approached us. The plane was at 14-15 km, when Dani ordered: "Azimuth 210, search!"


According to the book, P-15 (operate in UHF band) detected F-117 from 23 km, SNR-125 (operate in X-band) detected F-117 at distance less than 14 km.
P-15 claimed to have range = 150 km, assumming this is detection range is against target with RCS = 10 m2, this radar will detect target will RCS of -30 dBsm (0.001m2) from 14 km and it will detect target with RCS = -20dBsm (0.01m2) from 26 km, P-15 detect the F-117 from 23 km, therfore in UHF band -20 dBsm > F-117 RCS > -30 dBsm


There seems to be confusion in terminology here:

When radar system first detects something (gets radar return that crosses threshold values), nobody actually knows there is a target there. It might be just clutter echo or some anomaly in the system. Usually there needs to be at least 2 detections (preferably more, especially in lower frequency surveillance systems) before anybody (operator or computer) has an idea that they have actually detected a target. The radar detection range used in specs and equations is the range where they get the first radar return at some predetermined probability. Many specs published about older Soviet equipment use 50 percent probability which is still useless range in real world as it will generate far too many radar returns and false targets. This is why modern systems usually use 80 to 90 percent probability as that's more realistic value.

Basically there are three different ranges:
1. Radar system detection range. This is where radar receiver gets a target return that crosses detection threshold values. This is pretty theoretical range especially with low probability values as those would overwhelm the receiver and processing system (computer or operator in older radars).

2. Operator/automatic tracker detection range. This is the range where operator or automatic tracker realizes that they have actually detected a target. This is range where tracking process is started to actually track the target.

3. Tracking range where target is being actually tracked with enough information to commence engagement for example.

The 23 km range in that Serbian book seems to be the second range. They needed some more returns to be sure and so actual target tracking was commenced somewhat closer (about 18 km away). The first range could be significantly longer range but it could only be estimated reviewing radar video of that engagement. Maybe that's where the 50-60 km range in some quotes comes from.

It also seems that there is some confusion if it was actually P-18 or P-15 system that first detected the F-117. P-15 has 140 km detection range against 2.5 square meter target (with low 50 percent probability) and uses UHF frequencies. P-18 has somewhat longer detection range (175-250 km depending on mounting) using same criterias and uses lower VHF frequencies. In any case it's very clear that F-117 stealth features give it huge advantage even against low frequency radars. Regular fighter would've been detected at 3-4 times longer ranges for sure given the same circumstances.


Awesome explanation about radar detection and tracking ranges Hornetfinn! I agree with your viewpoint that VLO platforms can be devious adversaries in all radar frequency bands. To the radar operator noticing a very faint “ping”/detection at long range......is that a ghost/false target, clutter or a genuine VLO adversary? Good luck radar operator buddy, better flip a coin!!!!

It confirms my suspicions that VHF radar “anti stealth” fanbois are extreme simpletons!

I have to say (once again :P )........the Serbian SA 3 crew have mad skillz!!! Considering that the SA 3 requires a high degree of manual operation!
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Unread post11 Aug 2018, 04:33

eloise wrote:Book written by Serbia SAM crews who shot down F-117:
Suddenly on the observation radar, I see the target on azimuth 195, 23 kilometers away. The next circle on the observation radar clearly indicates that the plane is approaching us. I say: "Dani, this is going to us!" Days opened his eyes, looked at the screen, and uninterestedly followed the situation. The reflection approached us. The plane was at 14-15 km, when Dani ordered: "Azimuth 210, search!" As an assistant to the shooting man, I ordered that moment: "Antenna!" The commander of the battery began to point the guiding officer on the azimuth and the meat corner to the target - left, left: stop !, right, up, up: stop! - antenna. He switched on the radiation of the observation radar. That's when the cats and the mouse started playing. Who will be faster and more skilful. The guiding officer, turning three wheels at the same time, tries to find the target. We run for more than ten seconds in an unsuccessful search for the target. Ordering: "Stop Searching - Equivalent!" After a few moments, Dani again orders the new search azimuth 230, and I am the moment of radiation. Adrenaline is in the air. This road manager manages to see the target on his two screens, but in no way can he cover it with a cross-section of horizontal and vertical markers. The dots just shrink - it has to push them out, cover the goal in the cross-section of the two markers. At the moment when the target is in the cross-section of the marker, they can begin to be monitored by manual tracking operators - by plane F1 and F2 on their pointers. Then conditions were created for the guidance officer to monitor the goal by distance, and manual tracking operators to run launched missiles at the target that is in the cross-section of the marker. The goal is to run and maneuver. Again the radiation time is too long and I order: "Stop searching - equivalent!" After a few seconds, we try the same procedure, the third time on the azimuth 240. Very soon, after a few seconds, the guidance officer finds the target and reports that the goal is to maneuver. The dashboards of the guards are shaking, the operators are losing it. The radiation time was long and dark when I wanted to order: "Stop searching - equivalent", the monitor of the monitor, Dragan Matić, cried out, "Give it! Give it, I have it!"



He energically turned his wheel, trying to bring the reflection from the target to the center of the screen. He succeeded. The tracking operators managed to hit the target with a cross - cross-section of two markers and thus provide the conditions for launching the missile. Another tracking operator, Dejan Tiosavljević, reports that the goal is to have a large reflecting surface. That moment, I say to Daniel: "Take care that it's not bait to screw us." My thoughts on war experiences from Iraq passed through my mind when the united forces put up angular reflectors on unmanned aircraft and thereby increased the reflective surface. The Iraqi combat crew thought it was a real plane and began radiating a Nishan radar. At that moment, airborne hunters captured the radar-nišan location and then eliminated the missile from anti-aircraft missiles from the ambush. The guiding officer, Muminović, reports - the station follows the target, the target on arrival, a distance of 13 kilometers. At the same time, operators report - by F1 I follow the target, following F2 I follow the goal. Dani commanded: "Object Destroy, Method T / T Launch!"


According to the book, P-15 (operate in UHF band) detected F-117 from 23 km, SNR-125 (operate in X-band) detected F-117 at distance less than 14 km.
P-15 claimed to have range = 150 km, assumming this is detection range is against target with RCS = 10 m2, this radar will detect target will RCS of -30 dBsm (0.001m2) from 14 km and it will detect target with RCS = -20dBsm (0.01m2) from 26 km, P-15 detect the F-117 from 23 km, therfore in UHF band -20 dBsm > F-117 RCS > -30 dBsm

X-band radar.PNG

SNR-125 can detect target with RCS = 10m2 from 80 nm (148 km), according to radar equation, 10 times reduction in RCS will decrease detection range down to 56%, so a target with RCS = 0.001 m2 will be detected at 7.87 nm (or 14.5 km), F-117 was tracked and detect at distance less than 14 km so F-117 rcs in X-band is less than 0.001m2.


Great find Eloise!
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Unread post13 Aug 2018, 04:49

Maybe, I have made a mistake
Đorđe Aničić was in the cabin of P-18 (VHF) radar instead of P-15 (UHF)
https://www.in4s.net/obaranje-f-117a-pr ... /?lang=lat
The fact that the F-117A was downgraded from the third attempt is unquestionable. The first and second attempts to find the target in the air by the Nishan radar were unsuccessful. Sitting in the PRG view point toward the P-18 observation radar at one time on the azimuth 195, I notice three targets, 23 kilometers away. The next circle on the observation radar clearly indicates that the plane is approaching us. I follow him in the next round of the distance is 18 km. The operator of the observation radar P-18, Ljubenkovic's guide through the GGS (voice-of-speech) reports that we have a goal. Obviously we are following the same situation in the air.

I say, "Days, this goes to us!" Days opened their eyes, looked at the screen, and ignored the situation. Our approach was approaching us. The plane was at 14-15 km, when Dani ordered:

"Azimut 210, search!"

We run for more than ten seconds in an unsuccessful search for the target.
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Unread post13 Aug 2018, 09:10

michaelemouse wrote:
hornetfinn wrote:Basically there are three different ranges:
1. Radar system detection range. This is where radar receiver gets a target return that crosses detection threshold values. This is pretty theoretical range especially with low probability values as those would overwhelm the receiver and processing system (computer or operator in older radars).


Is this % calculated per pulse? If so, wouldn't sending 100s of pulses and using time integration get rid of the false returns pretty quickly? You might need 10 plots to get a track but if each pulse you send out has a 50% of crossing the threshold value and you send 10 000 of them per second, it shouldn't take much time to get a track. Maybe I'm missing something.


No, it's calculated using all those received pulses and radar system using all the tricks like signal processing and integrating those pulses. Basically it's the probability of the radar system detecting certain target at certain range after all is said and done. However that idea is correct in that sending and receiving more pulses and integrating those pulses and using signal processing to find targets from that does improve performance a lot though. Old systems (like P-18) can be improved a lot by upgrading them with digital components and signal processing.

Like this:
http://www.litak-tak.eu/uploads/Brochures/P-18ML.pdf

Modern systems which already do many of these tricks do not get similar boost easily and improvements are more modest.

michaelemouse wrote:
hornetfinn wrote:Thanks eloise. So it seems like they had both P-15 radar and also P-18 radar. That picture seems to indicate that the P-15 belonged to the battery and the battery also got support or had the P-18 system attached directly. Interesting to read about this from Serbian POV. It seems like they knew very well what they were doing and executed very well with such ancient equipment.)


I've wondered if they had some significant help. If I'd been Russia or China during the NATO bombing of Yoguslavia, I would have been very interested in exchanging information with the Serbs to know what it's like to face NATO air/naval assets & tactics. The F-117 was shot on March 27th and on May 7th, the Chinese embassy was bombed in what the US said a map/intel failure. I don't know enough to be sure but it might have been the equivalent of "accidentally" dropping a cup of coffee on someone you want to butt out of a conversation.


I doubt they really needed help for that, although they might've had chat with Russian and Chinese experts. They must've known by themselves that F-117 is difficult target and approximately know how it would seem like in radar screen even if they didn't know exactly its RCS plot. They must've known in theory how to engage it and what kind of tactics would help survive SEAD/DEAD efforts. They worked up very solid tactics to do that with their old equipment and had very good discipline to execute that tactics successfully.

From AD perspective F-117 is actually easy. Besides VLO is doesn't have much else to offer. It doesn't have extensive sensor fit or EW system like F-35, so it's flying almost blind and deaf in comparison to most other aircraft. It has flight performance more similar to bombers than fighter aircraft. This means it's mostly flying very stable and predictable flight path. Of course the problem is detecting and tracking it for successful engagement due to VLO stealth. All this means that F-117 itself must fly close to AD systems to allow successful engagement. This can happen if mission planning system doesn't know where the AD systems are during the mission. Serbs had very mobile tactics to survive SEAD/DEAD efforts and this also helped downing the F-117 as the mission planning for F-117 could not predict there was SA-3 battallion with P-18 radar almost directly under the flight path. I think F-117 really showed the power of VLO stealth due to these reasons. Only one being shot down after all it has ever done is really impressive.

Think about modern day versions. F-35 also has great VLO stealth, but it also has insane sensor fit with most advances sensor fusion system, insane networking, insane countermeasures system, very good maneuverability and flight performance.
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