MiG-21 radar nerfed?

Has a recent update nerfed the MiG-21's radar? It seems impossible recently to pick up contacts, even if they are above the horizon. It just seems to have been a problem for the last week or so and while I'm sure it is more realistic it has destroyed the boom and zoom tactic used by so many of the fishbed pilots in multiplayer.

I'm not complaining about this, I'm just curious what exactly has been done as I haven't seen any mention of it anywhere, but my friends and I have found ourselves at a real disadvantage since the change.

I have been flying the Mig21bis on Cold War Server for the past few months and used the radar missile quite a lot.

The latest patch show big changes to the radar. I made some tests . Mig flying behind a target F5 tiger at 200m 300m 400m 500m .

I flew the mig behind him above and below trying ground filter and tilting the antenna.

I could not see the Tiger at all with radar even when he is in visual range above the horizon...

Here is a screen shot of Mig 21bis cockpit with a Tiger II being tracked by the HUD reticle.

You can see the Tiger is flying above the horizon. The mig 21 is flying at 500m altitude and the Tiger is a little above that.

I tried many attempts to find the Tiger from above and below and the IR seekers would were detecting it and I could visually see it but the radar had not even a hint of anything.

https://ibb.co/j8pfo6

but would the SAPFIR do that in real life? at 500m? Don't seem possible. that seems real low. But I'll let the experts pipe in.

I have no real problem. Detects fine. Even low level if the targets are quite above me with the tilt up mode.

Detection of an F-5 by a player MiG-21bis does vary by height above terrain of the MiG. I followed a 5000m F-5 at ~26km and dropped altitude slowly. At the height of 290-300m over the ocean I lost the contact.

Given a target height of 1000m, own height of 425m, and 4.5km lateral separation I could get a radar contact with the radar in the high filter but not the medium filter mode.

It's fair to say that at low altitude the detection range is reduced based on some kind of ground interference. Don't expect to detect a target 20km away if you're at 300m and he's at 1000m despite being in a filter mode which looks level and above.

Dam i just wrote a long detailed explanation... and accidentally deleted it when i looked up and the forum was asking me to sign in :(

Cant be bothered typing it all again but here is a German site explaining using the Mig21 radar for detecting low flying targets

http://www.mig-21-online.de/Funkmessvisier/fmv_UEH.htm

I do miss the old mig-21 radar, it made it way more fun to fly against the modern fighters, but it's still ok, just don't expect to kill anything down on the deck using the radar alone anymore...

So is it confirmed that the Radar got problems to detect planes flying above or at the same altitude? If the mig is at or below 500m?!

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It seems correct to me both situations.

Coaltitude is something radars, even modern doppler ones, dont like at all.

And for the Saphir series the radar at low altitude is not reliable.

So is it confirmed that the Radar got problems to detect planes flying above or at the same altitude? If the mig is at or below 500m?!

 

 

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I would second Esac_mirmidon, this is absolutely normal behaviour when flying the MiG in low altidudes. I would strongly recommend to check the link by Dirty Rotten Flieger since this are first hand reports. Use the translator or if you need some specific points translated I would do it for you guys.

Wasn't there several post before of people exploiting the radar in the MIG-21 by doing rolls?

So is the OP saying he wants this behavior back? I thought this was a cheat?

Wasn't there several post before of people exploiting the radar in the MIG-21 by doing rolls?

 

 

So is the OP saying he wants this behavior back? I thought this was a cheat?

Hm, speaking in his own words he is not complaining about it but as a direct answer to him I would say the low alt radar performance (and I strictly comment only this case) has been made far more realistic which is the aim of a simulator. Your kills will decrease in numbers but get more satisfying if you master this bird.

I don't want the roll exploit back.

I just flew on cold war server in Mig21 against F5 and Viggen and let me explain what happens over and over...

I was flying at 10K and AWACS would call a target a 30 km 6000m hot, so i would dive toward them and turn radar on. I would see the contact appear I dove passed 7000m indicating they were below me. Then at 6000m it would indicate they were same height . When I got down to 5000m and the radar indicated I was below them I locked them and after a few moments they disappear off my radar screen.

I could not reacquire them even tho I was well below them and they were at 6000m right infront of me.

I had many occasions when I can see the enemy plane about 6 or 7 km in front of me and we are both in the contrails with me slightly below them and ....NOTHING. nothing on my radar. Unfortunately to take a screenshot i have to press two buttons at opposite ends of my keyboard and I can't do that with one hand....but if I could take those screenshots you would see that they were in the right place to be on my scope.

I pursued a contrailing F5 from his 6 o'clock slightly below him and kept turning on my radar as I approached him and it never once was able to see anything.

In the weeks since the patch I have played many hours in the Mig21 and many many times I get an AWACS call nearby and dive down below the contact, see it on my radar for a few moments indicating it is above and in front of me and then it disappears and I cannot reacquire it . Very often I can see the contrail right in front of me but the radar says there is nothing there.

This just can't be right.

Also in pursuit of realism ... In real world Mig21 was not he only Red plane facing so many superior blue planes . This is in fact a game and until we have some other Red planes to help the Mig21 online, it is debatable if is a good for the game to nerf it like this.

Also I nearly forget to mention ....from the German Mig21 site ... English google translations says that it is possible to take actions that reveal the lower flying targets position through the ground clutter with enough clarity to continue an intercept ,even though the target cannot be locked...

"'To clearly distinguish the air target from earth faults, the interrogation query can be turned on. However, this may only be done for a short time, because during this time no positional signs are written and consequently the height grading to the air target can not be determined.

3. If, despite all measures, the target character with the position mark is not recognized, press the delete key briefly. Usually, after that, the real air target is written on the screen fractions of a second earlier than the earth faults.

"Zum eindeutigen Unterscheiden des Luftziels von Erdstörungen kann die Kennungsabfrage eingeschaltet werden. Das darf jedoch nur kurzzeitig erfolgen, da in dieser zeit keine Lagezeichen geschrieben werden und demzufolge die Höhenstufung zum Luftziel nicht bestimmt werden kann.

3. Wird trotz aller Maßnahmen das Zielzeichen mit den Lagezeichen nicht erkannt, ist kurzzeitig die Löschtaste zu drücken. In der Regel wird danach das reale Luftziel um Sekundenbruchteile früher auf dem Bildschirm geschrieben als die Erdstörungen."

http://www.mig-21-online.de/Funkmessvisier/fmv_UEH.htm

German site talks about RP-21 Spin Scan and not RP-22 Jay Bird (NATO code names) which is carried by bis-SAU. There is much in common but also major difference.

At lower altitudes the detection range is limited to less than the geometrical scan volume but 6km should not low altitude enough for this to happen.

If you can find a repeatable scenario of targets not being detected inside the scan volume suitably far from ground interference I would much like to see them.

There is already a misunderstanding that targets <150km/h aren't being shown on the radar unless the LST filter button is on (when it should always show all contacts regardless of speed).

German site talks about RP-21 Spin Scan and not RP-22 Jay Bird (NATO code names) which is carried by bis-SAU. There is much in common but also major difference.

 

At lower altitudes the detection range is limited to less than the geometrical scan volume but 6km should not low altitude enough for this to happen.

 

If you can find a repeatable scenario of targets not being detected inside the scan volume suitably far from ground interference I would much like to see them.

 

There is already a misunderstanding that targets <150km/h aren't being shown on the radar unless the LST filter button is on (when it should always show all contacts regardless of speed).

This is correct. 6km seems to high. Distortions should be visible up to 3km in level flight regarding a polish manual but experience tells me that between technician storys, pilot stories and manuals is place for a whole universe.

Here the excerpt translated from polish by myself so sorry for any misleading phrasings.

In summer, in small heights above the earth's surface (up to 3000 m), reflections from land-based objects are displayed on the radar screen. This zone of reflection is normally drawn as blurred areas extending from 0 km to the distance corresponding to the altitude of the flight (e. g. when the aircraft is at altitude). 3,000m above the earth's surface become blurred areas from 0km to 3 km). These blurred areas could obscure the actual target and must therefore be filtered.

The filtering is triggered by the H. SIGN switch. is located in block 19 (PUL 6T 19). However, the filtering may not be sufficient (e. g. if the aircraft is flying below 3000 m in a mountainous area where blurred areas appear at several points on the radar screen, for example), the pilot has to raise the localisation antenna by 3.5 o. with the MAL switch. INSERT is also located on block no. 19 (PUL6T 19).

Following this thread...

I for one am having a difficult time with this bird, and flying in MP. The little F-5's seem to pop up everywhere, and I can't see them with either my Mk1's or the Radar.

Following this thread...

 

I for one am having a difficult time with this bird, and flying in MP. The little F-5's seem to pop up everywhere, and I can't see them with either my Mk1's or the Radar.

Yes, but this is the way its supposed to be. The F-5 is small an difficult to see. But your opponent should have the same issues as the 21 is really small compared to the Phantom f.e.

Regarding the radar it depends on mission design because this plane was not build to take off and go out for search and kill. Everything is about GCI or if you like Awacs. As long this is not working as intended you can't expect the full MiG-21 experience no matter which bugs or features remain.

Even if the german site is focused on the RP-21 I would recommend to take a look since descriptions of needing 3 approaches in bad weather for a successful intercept even with GCI shows a bit of the complicated life as a 21 pilot.

The hard truth is that the fight is unfair but not impossible in its current state but even if M3 would solve all open issues tomorrow we would have to wait for some fixes by ED. But btw, nobody told that the RL life is fair. In the end 95% depends on the pilot and as a wise men said: Loose sight, loose the fight.

P.S. It took me nearly 6 months of training learning to maneuver and keep my opponent visual 90% of the time.

Not picking up a target on scope that you are chasing which has the same speed is inherent with all DCS radars, FC3, Mirage etc.

It's not a bug but a feature.

correct me if i am wrong,

but the "Same speed- not on scope" is because the a Pulse Doppler radar filters the contact out because it thinks its Groundclutter.

afaik, the Migs21 radar isnt a PulseDoppler one, so this should not happen right?

correct me if i am wrong,

but the "Same speed- not on scope" is because the a Pulse Doppler radar filters the contact out because it thinks its Groundclutter. afaik, the Migs21 radar isnt a PulseDoppler one, so this should not happen right?

If he's above you, there's no pulse-doppler filtering anyway with PD radars. But, the radar PRF plays a role here as well as whether the target range is increasing or decreasing (not sure what exactly is simulated in the game, though).

IIRC, there is a low speed target switch in the MiG-21 for such cases. Did you try using it for the rear-hemisphere targets?

correct me if i am wrong,

but the "Same speed- not on scope" is because the a Pulse Doppler radar filters the contact out because it thinks its Groundclutter.

afaik, the Migs21 radar isnt a PulseDoppler one, so this should not happen right?

Correct, the 150 km/h limitation is a tracking issue not a detection issue. If you fly behind a 75km/h contact it will produce a blip on scanning radar to see. However if you try to try to lock on the radar will reject it as chaff or other undesirable false contact.

The LST button turns off this chaff-tracking protection so it is possible to lock on to slow contacts (chaff, clutter, or legitimately slow aircraft). But in all cases the slow contact is displayed the same as a fast one in the scanning mode.

F-5 detection with MiG-21bis module has been problematic. In some versions of the software an F-5 next to another aircraft (e.g. F-15) the F-15 is displayed but the F-5 is not. So every test for general radar performance should be done against a type other than F-5. F-5 may be a special case of behavior.

A test at 4km trail of a MiG-21bis and F-5 in 1000m spread formation. At a 160m stepdown the player MiG-21 displays the MiG-21 at ranges only less than 25,000m. The F-5 however appears at ranges disappears from the scope as range increases beyond ~28.5km.

By using the AI follow command to enforce a formation of different types in exact relative position it is shown that the MiG-21bis radar has different behavior for different target types.

correct me if i am wrong,

but the "Same speed- not on scope" is because the a Pulse Doppler radar filters the contact out because it thinks its Groundclutter.

No, I don't know what makes same speed contacts disappear from scope but this is not ground clutter filtering.

Same speed makes you distinct from ground clutter.

Only having the same relative speed as the ground will make you similar to ground clutter.

Example, let's say your radar frequency is 100MHz, a ping to the ground will return a frequency higher than 100Mhz.

The doppler formula will return a relative speed for this contact. Same return frequency makes relative speed 0, higher frequ makes relative speed >0 (closing in), lower frequ makes relative speed <0.

The formula to calculate the ground speed (in one axis) of the contact is: [ownship ground speed] - [relative speed calculated with doppler formula].

If the relative speed of the radar return is equal to your own ground speed, the result for the ground speed of the contact will be 0 (or lower than a certain threshold to account for inaccuracies), it means that you're pinging something that didn't move relative to the ground.

That's why a defender will maneuver perpendicular to the attacker trajectory, to make a ground speed 0 so the radar rejects the return as ground clutter.

If you ping something that has same speed as ownship, the frequency in return will be exactly 100Mhz, so the doppler formula will return 0 for the speed differential. So you can deduce that the ground speed of the contact is equal to your own ground speed, therefore it's a moving object relatively to the ground.

Not detecting aircraft who match your speed is a problem associated with Pulse Doppler radars. However, it is not because the targets doppler shift is the same as the main-beam ground, the relative closing velocity between the radar and the main-beam ground is high (example, 300 knots), but the relative closing velocity to the jet you are chasing is close to 0 (as they match your speed).

The reason its difficult to track targets with almost no doppler shift is because of the 'altitude line' clutter in the frequency spectrum.

Your airborne radar has sidelobes. While weaker than the half-power main-beamwidth often referenced in manuals, if reflected off a massive RCS object these sidelobes can hinder your radars performance.

Well it turns out that the ground below you has a huge RCS. The sidelobes from your antenna will radiated energy in many directions (including downward) which can reflect back up into your receiver. Because you are for the most part maintaining your altitude, the doppler shift of the altitude return is centered around zero.

Below is a picture of the doppler spectrum. The alitude line clutter is centered on your radars actual transmit frequency.

As you can imagine, sidelobes emitted 90 degrees downward from your heading have zero doppler shift. But sidelobe energy emitted at 87 degrees downward would have a slightly positive doppler, and 93 degrees slightly negative.

But as you expand away from the 90 degree altitude line, the energy emitted is more likely to reflect away from you then back up at you. Thus its mostly the energy emitted directly below you (at 90 degrees) that has a significant impact on your receiver.

Targets can hide in this portion of the doppler spectrum just like they can in the "main-Beam ground clutter" (the doppler notch). Pulse doppler radars have special thresholds for these regions so that clutter is not processed as an actual return and displayed on the scope (false target).

Using a low PRF, radars can employ Sensitivity Time Control (STC) to gradually increase the sensitivity of their radar receiver. Doing so decreases the amplification of close proximity returns, like sideloe ground clutter. This makes it possible to significantly reduce sidelobe clutter, including the "altitude Line" clutter. This is why engineers say low PRF waveforms have 'good main-beam performance'. Its also one of the reasons why you might use a low PRF for ground mapping in a pulse doppler radar.

Regarding MiG-21 it has a prevention of tracking objects which are approaching in a +-150km/h window relative to the speed at which the ground approaches. It will detect targets at any speed in the scanning mode.

For example if MiG is flying 900 km/h TAS then it will prevent tracking of objects which are closing between 291 and 236 m/s. MiG will happily track another airplane going 900 km/h because its closure is 0 m/s which is outside the range 236-291 m/s.

Tracking prevention is attempting to avoid tracking chaff which very rapidly slows to 0 km/h TAS when released by a target. A chaff at 0 km/h TAS approaches the MiG at a velocity equal and opposite to its TAS (MiG has no way of knowing wind so must assume TAS = G/S).

I don't know if the screenout functions in only the radial direction or not. E.g. if attempting to track a fast target which is beaming will track be prevented because closure is in the rejected range or is radar smart enough to realize it is moving sideways fast enough to not be chaff?

So LST button is to allow tracking of returns that would otherwise be rejected as possible chaff or not valid. Remember that all of this rejection is only for tracking. Detection and display are unaffected by target speed.

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Beamscanner, it is interesting how MiG-21bis will not display contacts when MiG is low to the earth. Do you think radar is reducing gain dynamically and so detection range of airplanes is reduced or is it LNS modeling shortcut "should make a mark on the scope but should be impossible to find this airplane in all the clutter so we'll just not display it instead"?