reported AGP-68(V5) Radar Azimuth and Elevation Bar issue

[skywalker22]

I would like to point out something about the AGP-68(V5) radar and it`s Radar Azimuth and Elevation Bar Scan.

There is practically no difference between settings (A1,1B or A6,4B and all in between), or if there are, are really, really small. My examples are F-16 vs multiple fighter jets, nose hot at approx. same altitude. I also did one example track with altitude difference. Results were the same. Is this how it should suppose to be? I would imagine having  bigger differences.

Ax=Azimuth, xB=Bars

 

f14_a1-1b.trk f14_a6-4b.trk f16_a1-1b.trk f16_a6-4b.trk jf17_a1-1b.trk jf17_a6-4b.trk m2000_a1-1b.trk m2000_a6-4b.trk mig29_a1-1b.trk mig29_a6-4b.trk su27_a1-1b_look-down.trk su27_a6-4b_look-down.trk

[BIGNEWY]

5 minutes ago, skywalker22 said:

There is practically no difference between settings (A1,1B or A6,4B and all in between), or if there are, are really, really small. My examples are F-16 vs multiple fighter jets, nose hot at approx. same altitude. I also did one example track with altitude difference. Results were the same. Is this how it should suppose to be? I would imagine having  bigger differences.

I will take a look at this in the morning, but as I have already mentioned to you, you are incorrect with your assumptions. 

[5ephir0th]

Wait, you expect to increase the detection range by reducing bars/azimuth? Thats not how it works, you get a better refresh rate on a smaller fov, not more detection range

[Raptor9]

@skywalker22, the azimuth and elevation settings adjust the total volume of airspace being scanned by the radar as the radar antenna itself is mechanically moved back and forth and up and down in sweeping motions. These settings do not change the output power or the sensitivity of the radar antenna to radar reflections, they only adjust how much physical airspace is being scanned within each scan pattern.

The only effect on "detection range" that these settings have is not the range at which the aircraft can be detected, but rather when they are actually seen by the radar. If an aircraft is in a block of airspace that is scanned at the end of the radar search pattern, then yes that fighter won't be seen until later in the scan compared to an aircraft that happened to be in a block of airspace that was scanned at the beginning of the search pattern. But it's not because the aircraft wasn't able to be detected at that range compared to the other aircraft, it's the fact the radar hadn't physically looked at that area yet.

If you scan using 1 bar of elevation and +/- 10 degree azimuth, that is a very small chunk of airspace that is rapidly scanned again and again within moments. If you set the radar to 4 bar elevation and a +/-60 degree azimuth scan, it will take longer to scan that much airspace; but these settings do not affect detection range.

[Frederf]

There is an assumption here that subsequent scans are not cooperating. If a return from a target is 90% of the level required for the radar to conclude that a signal is a genuine contact then it is below the display threshold and not shown. However if several very similar, rapid returns of 90% confidence level are received it is certainly within the imaginable design of a radar system for these sub-threshold returns to be combined into a positive contact that exceeds the display confidence threshold.

It is my belief that the APG-68 operates by such a principle and that rapid weak detections can result in a displayed contact where a single will not and multiple widely-spaced returns either will take longer or may not at all. The APG-68 has enough memory to make use of such a technique. Under such a scheme a focused scan pattern may reveal a target at a farther distance and/or sooner than a less-focused scan.

[RuskyV]

So by scanning an area with the radar set to a smaller scan volume you could in theory pick up a target further out? 
 

 

[skywalker22]

  

14 minutes ago, RuskyV said:

So by scanning an area with the radar set to a smaller scan volume you could in theory pick up a target further out? 

I don`t think so. The distance depends on the radar power, which is the same for any type of scanning.

---

@FrederfAnd how many times does the radar have to scan a contact within these 90% of signal quality, that is considered as valid and shown on B-Scope of FCR page? Is one time enough?

Edited June 30, 2022 by skywalker22

[BIGNEWY]

is there any unclassified evidence to support this? If so please PM me. 

thank you

[Sacarino111]

2 hours ago, Frederf said:

There is an assumption here that subsequent scans are not cooperating. If a return from a target is 90% of the level required for the radar to conclude that a signal is a genuine contact then it is below the display threshold and not shown. However if several very similar, rapid returns of 90% confidence level are received it is certainly within the imaginable design of a radar system for these sub-threshold returns to be combined into a positive contact that exceeds the display confidence threshold.

It is my belief that the APG-68 operates by such a principle and that rapid weak detections can result in a displayed contact where a single will not and multiple widely-spaced returns either will take longer or may not at all. The APG-68 has enough memory to make use of such a technique. Under such a scheme a focused scan pattern may reveal a target at a farther distance and/or sooner than a less-focused scan.

HI.

Inr¡teresting one, never thought about that design feature, IF real , what a good one!

Thanks for your thoughts, always interesting and instructives.

Saca111

[skywalker22]

I don`t know how accurate are these data, but finally I found some tangible information about how radar antenna work and moves:

https://www.f-16.net/downloads/Falcon_4_Manuals/f4_AN-APG-68-v5.pdf

From the context: Bar Scan The next control that the radar allows is the Bar scan setting. The AN/ APG68(V5) scans the horizon by physically moving the antenna. The beam that the antenna normally emits is not able to scan more than 4.9 in the vertical.
 

 

The Bar Scan function effectively removes this situation by moving the radar up 2.2 at the end of each scan in the horizontal. The amount of extra ‘bars; in the scan are indicated by the bar scan control. With this set to 1, the radar will scan just the single 4.9 slice of airspace. Set to 2, the radar will scan 2 bars of airspace; set to four it will scan four bars. The diagram above shows this pictorially and makes it much easier to understand. The disadvantage to using the Bar Scans however is the increase in time to perform a complete sweep of the area. It takes 2.5 seconds to scan one bar (at Azimuth 60deg), and another 0.5 seconds to move the antenna up and start on the next bar, so a full 4 bar scan will take 12 seconds (that means radar targets only get updated every 12 seconds.), whereas a 1 bar scan will take just 2.5 seconds (at Azimuth 60deg - in case of using Azimuth of 10deg the time is way shorter). 

Which means, that the time when a Contact is acquired using A1, 1B or A6, 4B cannot be the same. Sure it depends where on that scan path the Contact is acquired (at the beginning or at the end), but surely there must be a difference between these 2 examples in most of the cases.

Edited June 30, 2022 by skywalker22

[5ephir0th]

59 minutes ago, skywalker22 said:

Which means, that the time when a Contact is acquired using A1, 1B or A6, 4B cannot be the same. Sure it depends where on that scan path the Contact is acquired (at the beginning or at the end), but surely there must be a difference between these 2 examples in most of the cases.

As you said, the TIME cannot be the same, not the range.

If you change from 4 to 2 bars, you will scan half the volume but at the double refresh rate.

Think about it, per example, you set 4 bars at 30 azimuth, the time the radar take to complete 1 bar at 30 azimuth is 3 seconds (just an example)

• Bar 1 (top one): 3 seconds,
• Bar 2: 3 seconds
• Bar 3: 3 seconds
• Bar 4 (bottom): 3 seconds

If the targets is at the scan volume that takes the bar 1, once completed that bar you have to wait at least 9 seconds to search again on that zone, so the target has been getting closer at that time.

An example, we can detect the target at 56 miles, target is located on scan volume of bar 1, 4 bar and 30 azimuth:

• Bar 1: target is at 60 miles, we cant detect it yet
• Bar 2: target is at 58 miles, we cant detect it yet
• Bar 3: target is at 56 miles, already in detection range but we are looking at another altitude
• Bar 4: target is at 54 miles, as above is already on detection range but searching on wrong altitud
• Bar 1 (again): target at 52 miles, now we are looking at the correct altitud, detected!

Now same as above but with 1 bar 30 azimuth:

• Bar 1: target is at 60 miles, out of range
• Bar 1 (again): target is at 58 miles, out of range
• Bar 1 (again): target is at 56 miles, in range, detected!

So, with 4 Bar we detect it at 52 miles but with 1 Bar we did at 56 miles, this mean that with less bars the detection range increase? No, it just increase the refresh rate, the differences depends on timing and closure rate

Edited June 30, 2022 by 5ephir0th

[skywalker22]

1st of all, I have to say Sorry to @BIGNEWY, I was incorrect. My test weren`t done in a proper way. I was always using just one single aircraft as my Contact. Today I repeated whole thing, but this time with 10 aircrafts, and on different altitudes (from min to max - what the APG-68 radar can detect). I was always using Azimuth of 60deg, and I wanted to see the difference when using different Elevation Bars scan mode, so I did example with 4 bars, and 1 bar. I also saved videos, but didn`t have time to upload them yet.

Conclusion: using different Bars settings really does make a difference, and a huge one, specially noticeable on acquiring multiple targets.

So here are the results.

 

Su-27_10planes_10k-37k_RWS_A6-4B.trk Su-27_10planes_10k-37k_TWS_A6-4B.trk Su-27_10planes_19k-25k_RWS_A6-1B.trk Su-27_10planes_19k-25k_TWS_A6-1B.trk

ps: about Radar Azimuth (Scan Width), I am sure the results will be similar to Bars, so wider (60deg) azimuth means longer time to acquire multiple targets. Using 10deg will take less time on multiple targets.

[BIGNEWY]

thanks for letting us know and for the DM in discord

[5ephir0th]

I must be wrong but on those four videos the detection range is the same, 45nm.

 

if you are talking about that with more bars you detect more targets on different altitudes of courses you are scanning a bigger space volume 

Edited June 30, 2022 by 5ephir0th

[Aquorys]

10 hours ago, RuskyV said:

So by scanning an area with the radar set to a smaller scan volume you could in theory pick up a target further out? 

I have my doubts about "further out", but quite certainly "faster", simply because you are scanning the same region more frequently. As a side effect, it might just pick up a target further out, because if you are scanning very frequently and therefore more often, there is obviously a greater chance that you will get good radar returns, especially if the target is maneuvering and thereby producing radar returns of varying intensity and quality.

That is also pretty much the entire idea behind the "spotlight search" that you get if you hold TMS up.

[skywalker22]

3 hours ago, 5ephir0th said:

I must be wrong but on those four videos the detection range is the same, 45nm.

 

if you are talking about that with more bars you detect more targets on different altitudes of courses you are scanning a bigger space volume 

 

But not for all 10 aircrafts. You see the difference with 1 bar or 4 bars? With 4 bars all 10 aircrafts appear only at 29nm in RWS mode. In TWS to get all 10 as Track targets, it only happened at 24nm.

[RuskyV]

13 hours ago, Aquorys said:

I have my doubts about "further out", but quite certainly "faster", simply because you are scanning the same region more frequently. As a side effect, it might just pick up a target further out, because if you are scanning very frequently and therefore more often, there is obviously a greater chance that you will get good radar returns, especially if the target is maneuvering and thereby producing radar returns of varying intensity and quality.

That is also pretty much the entire idea behind the "spotlight search" that you get if you hold TMS up.

Makes perfect sense to me, thanks for explaining 

[FusRoPotato]

What you will be able to see on radar depends on far more than just the power you plug into it. Increasing power or sensor surface area/count is just the general brute force method to getting better results. As the 16's radar evolved, it received very large performance enhancements just from filter processing alone. 

If a specific target is always detected at 35nm but not 36nm, regardless of radar and aircraft, I'd say that simulation is neglecting a few physical concepts and simplified estimations. A higher fidelity simulation, of which is still heavily reliant on basic simplifications, would account for small RCS variations based on airframe perturbation thru RNG, the shifting of backgrounds, sensor alignment, and the amount and frequency of power received from a painted object. Think of it this way, if someone takes a bunch of pictures of you, there's a chance some of them are going to resolve the tiny dot on your shirt while others won't. There wasn't supposed to be enough resolution in the camera to see that level of detail, but it will sometimes show anyways as a pixel larger than the dot itself. It's how we are able to build pictures of a black hole by stitching together many photos from different angles, or clearer pictures of the galaxy with exposure time.

The whole point of reducing bars and azimuth is to get more pictures, not just for more updates, but for clarity as well. The concept of power is not exclusive to the wattage plugged into the unit, it is a summation of the energy you get back from targets you're looking for. That factor includes RCS, how often it is painted, and how well it can be filtered. What matters is how much energy over time that target sends back and whether or not your filters are strong and lucky enough to isolate it from the surrounding noise to recognize it for what it is. There's a higher chance of receiving faint returns at a greater distance in a shorter period of time if painted more frequently. 

The amount of power a target sends back doubles when halving the azimuth. It doubles again when halving the bars. That also means the power of the noise doubles as well, but noise does not always scale the same and the filters have an increased chance of recognizing something. Correct-as-is for a game maybe, but not real life. Reduced azimuth and bars should be enhancing range.

Edited July 5, 2022 by FusRoPotato

[TheBigTatanka]

What Fusropotato wrote matches with what I've been told by several fighter guys: that by narrowing the beam, you are getting many more returns back (because the radar is hitting the target that much more) and you can see and lock things much much further away than you would normally be able to. One example had to do with being able to lock a tanker at much further than normal detection range when commanding an STT lock at the bullseye location and elevation provided by AWACS. Another example had to do with being able to hold a lock on a contact at a further range than you would normally be able to detect it -- for example, let's say you can normally see a fighter at 50nm and lock it there -- you might be able to hold the lock on that fighter contact out to 70nm because the radar has concentrated its energy. The same applies for narrowing the scan.

I need to do some testing and make some tracks, but i get the sense that it's not working like this when you spotlight aircraft with TMS up long. I can't seem to detect contacts where i have datalink tracks by using spotlight at any range beyond what i would normally get a hit at on a 30 azimuth and 4 bar scan.

Sent from my Pixel 3 XL using Tapatalk

[RuskyV]

From what I have seen the the radar will only update a contact faster if within range of a standard sized fighter, providing more updates within the normal detection ranges. I’ve not seen it effecting detection range. It’s of little practical use to spotlight when you can gain the same/better info entering SAM mode with regards to target motion.

Strange the the radar will pick out an il76 at 50+ nm with a standard 4 bar scan at 120 azimuth, giving sufficient returns to be able to STT.
 

It seems like an arbitrary number is given for fighter size and when it is detected, depending on the module being used of course. For the viper it seems to always be just under 40nm.

 

Edited July 17, 2022 by RuskyV

[Hobel]

Am 30.6.2022 um 08:11 schrieb Frederf:

It is my belief that the APG-68 operates by such a principle and that rapid weak detections can result in a displayed contact where a single will not and multiple widely-spaced returns either will take longer or may not at all. The APG-68 has enough memory to make use of such a technique. Under such a scheme a focused scan pattern may reveal a target at a farther distance and/or sooner than a less-focused scan.

I mean, that's exactly what the M2000 does in DCS?
If you reduce the search range, the probability of detecting targets at a greater distance is higher, because the space is scanned more often.
Radar does not simply stop fixed values

 

a good example picture and we don't have that in DCS yet.

Edited September 11, 2022 by Hobel

[Moonshine]

any news on this? i get it, lower bar settings do not increase radar power so you technically dont get more range out of the radar. however lower scan area, more scans, more returns should in fact apply as TheBigTatanka said here:

On 7/17/2022 at 7:02 AM, TheBigTatanka said:

What Fusropotato wrote matches with what I've been told by several fighter guys: that by narrowing the beam, you are getting many more returns back (because the radar is hitting the target that much more) and you can see and lock things much much further away than you would normally be able to. One example had to do with being able to lock a tanker at much further than normal detection range when commanding an STT lock at the bullseye location and elevation provided by AWACS. Another example had to do with being able to hold a lock on a contact at a further range than you would normally be able to detect it -- for example, let's say you can normally see a fighter at 50nm and lock it there -- you might be able to hold the lock on that fighter contact out to 70nm because the radar has concentrated its energy. The same applies for narrowing the scan.

 

at the moment with how hardcoded the radar values are (same example is the lookdown subject) i bet it just wont make a difference to what bar setting you put it to, as skywalker explained in his original post.

[skywalker22]

On 9/11/2022 at 11:53 PM, Hobel said:

I mean, that's exactly what the M2000 does in DCS?
If you reduce the search range, the probability of detecting targets at a greater distance is higher, because the space is scanned more often.
Radar does not simply stop fixed values

 

a good example picture and we don't have that in DCS yet.

 

Good point, I would also like to know how is our AGP-58(v5) work in DCS. @BIGNEWYcan you check it out? If there is any difference in detection range with smaller bar scan.

thx a lot.

[BIGNEWY]

4 hours ago, skywalker22 said:

Good point, I would also like to know how is our AGP-58(v5) work in DCS. @BIGNEWYcan you check it out? If there is any difference in detection range with smaller bar scan.

thx a lot.

We have more information and we will be adjusting based on the data we have. 

thank you