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[FIXED] JF-17 Radar beam updating target true position in the notch (TWS only)

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Dear Devs,


JF-17's Radar beam is updating target true position in the notch instead of extrapolating the data.

The radar memory gets reset everytime the radar beam crosses over the target. Therefore the target box (on the HUD) extrapolation returns to the true target's position. It's more pronounced to lower azimuth scan settings.

In the end the radar can't be notched unless target is terrain masking. THIS IS ONLY AFFECTING TWS.

Whenever attempting to STT the target, the radar wlll return to scan mode and the target track can be lock-on (again) in TWS.


Please find attached track + tacview.


Thank you

Best Regards


JF-17_radar_cant_be_notched.trk JF-17_radar_cant_be_notched.acmi

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Can confirm, even with a blinking TD box on the HUD (meaning radar did not find the target in the sweep at the expected location and it has entered MEM mode), the radar will still magically update itself with the target's true location and heading and will not drop the lock, no matter how long the radar says it "can't find the target".


Also happens in SAM and DTT modes.


Notching in STT behaves as intended and will drop lock after TD box blinks, and it will also not show the true location of the target while it blinks/target is lost.

Edited by J20Stronk
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  • 2 weeks later...
  • uboats changed the title to [CHK] JF-17 Radar beam updating target true position in the notch (TWS only)

if contact is not detected by radar in one scan frame, its trackfile will go into prediction mode, and trackfile max keep time timer(8.0s) will start count down.

if it's detected any time in one scan frame, trackfile updated and the timer is reset, thus, TWS/DTT contacts will not disapper immediately, and stay last known/predicted position within timeout limit(8.0s).


in TWS/DTT, you are tracking a trackfile, it may or may not represent the real target, depend on when it's updated.

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The thing is, even though the radar enters MEM mode, the HUD TD box and trackfile in RDR page will still update the target's position when the beam goes over the it. After the update, the radar will still remain in MEM mode, with TD box flashing.


After the 8 seconds, the bugged target will not be dropped from the radar, but only if it's bugged in TWS or SAM. STTs do drop after the timeout.

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trackfiles are not displayed only after one scan frame, radar page refresh many times per second.

hpt/spt trackfile will be predicted anytime they are displayed to provide proper SA for pilot, instead of jumping around after scan finished.

HUD TD box and trackfile in radar page may jump a bit while contact is in MEM mode, but it is caused by no-perfect prediction(no accelaration info), totally different reasons.


anytime HUD TD box flashing, it means trackfile is predicted, not direct ping from contact, and the trackfile data is not so reliable for guidance,

but it will not be dropped immediately, pilots need SA reference even it's degraded.


in TWS/SAM mode, we have no reason to drop hpt/spt trackfile immediately if they are in notch,

because radar is centered very close to hpt, we have good chance to find them out again, until 8s timeout reached.

the target have to stay in notch > 8s, anytime he run out of notch and pinged by radar within 8s timeout, trackfile will be upated, timer will be reset, and trackfile  will be marked as solid ping.

Edited by L0op8ack
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I've made a .trk file to show what I mean.


I had a MiG-21 fly towards me then make a 90 deg. turn right while also dropping it's speed to have it notch my radar. As you can see, my radar enters MEM mode two times: once it dropped for about 3 seconds before it reacquired it and kept a solid lock, but then shortly after it entered MEM mode again.


During that second MEM mode period, you can see the TD box jumping backwards ever so slightly as if it was updating target position, even though the TD box was blinking meaning it's still in MEM mode and it supposedly can't find the target. 


Not only that, the TD box blinked for a solid 32 seconds after the radar entered MEM mode that second time.





Also worth mentioning: in the track file I show off 2 more bugs that I have discovered involving Velocity Search.


First is the fact that VS mode will show the range to any detected targets on HSD with Datalink on. This is obviously not possible since VS does not measure range at all, only target velocity and bearing. (there were no AWACS in the mission, only me and the MiG)


Second is that hits found in VS can transfer over to other radar modes, allowing you to bug them in RWS/TWS at a much greater distance than either of those 2 modes can normally detect and/or track targets. You can see when I switched to TWS, the VS hit was visible and trackable, but when I let the radar sweep over it in TWS without bugging it, the trackfile disappeared. 


Normally, TWS will find this MiG at 35nm with the variables from this scenario. In the .trk VS picked him up at 55nm, at which point you could S2 Left twice to go to TWS and quickly bugged the target before the radar clears the trackfile.



Thank you for your time.

JF AA radar bugs.trk

Edited by J20Stronk
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in TWS/SAM scan process, radar beam will not always point to hpt/spt within one full scan frame, we need predict their position when beam is not point to them.

the only problem I see is: whether we should mark trackfile as MEM or not, after we had a solid ping-echo from target.

in current implement, we mark it as MEM too, because in fact it's predicted when radar beam is not point to them.

the reality: MOST OF TIME in TWS/SAM SCAN, trackfiles of hpt/spi are predictions.


if we mark trackfile as solid/precise while in fact it's predicted after the solid ping-echo,

the difference between real target position and TD box will be very obvious, pilots may be confused and misunderstand.


We'd like be honest: flash if trackfile IS predicted.

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Well i understand your point of view & I completely disagree. The current behaviour isn't really as you describe unfortunately.

The Problem is the BEAM of JF-17 radar has literally no NOTCH filter. You can fly with a closure rate of 0 knot it will still see the targets.

The prediction system works but the beam sees everything therefore your 8+ secs memory doesn't make any difference.


ED Core feature regarding the Notch filter has 2 differents values. Targets are notching when the closure rate is below 80 knots (when above 5 NM). 40 knots Below 5 NM.

You cannot lose a trackfile in TWS since the beam has no Notch filter & sees true positions of the targets at every BAR swipe.




The only way you can lose the trackfile in TWS/SAM if the target is terrain masking (all about line of sight). I'm more than happy to give you a live example 🙂

I can notch forever airborne radars of any jets in DCS. 

Also if the target flies too low and the prediction send TD BOX under the map, you can still lock on the target right after you lost lock since the beam sees him.


This issue makes the JF-17 not in-line with all the other modern jets modules, regarding radar and memory.

Edited by Old Sauveur
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Here is a track from a Helicopter flying at 1 Knot AND in a beam on top of that (which is unnecessary). In any other jet in DCS, no Pulse Doppler radar can't spot it in lookdown. Somehow JF-17 keeps the lock on memory with TRUE position of the target all the way in TWS. You can see the track was kept in "memory" way more than 8 secs, almost 4 min.

This shows that in TWS the Radar beam has no notch filter.

JF-17 no notch Filter.trk

Edited by Old Sauveur
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On 1/14/2021 at 10:52 AM, Old Sauveur said:

Here is a track from a Helicopter flying at 1 Knot AND in a beam on top of that (which is unnecessary). In any other jet in DCS, no Pulse Doppler radar can't spot it in lookdown.


The helicopter rotor is like a noise jammer, it direction is known by everything basically but range can be challenging as it is constantly moving to all directions at various speeds, and there is two of them even in total.



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  • uboats changed the title to [FIXED] JF-17 Radar beam updating target true position in the notch (TWS only)

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