need help using radar in F-15C

[GGTharos]

4 hours ago, Nahen said:

For those interested, I will add that depending on the vertical position of the cursor, we influence the "speed" of radar search by narrowing or expanding the vertical range of the antenna.

Four things affect how fast the radar volume is scanned as per the real F-15 radar manual:

1. The radar mode (eg. VS scans the antenna at 35 deg/s, while most RWS/TWS functions scan it at 70 deg/s) - there's no VS radar mode in our FC3 eagle
2. The number of bars selected for the scan
3. The azimuth selected for the scan
4. The selected VSD range (at 20nm or less, the antenna is scanned at 90deg - I forget if this is implemented in DCS.  At that range the bar also gets redefined to be ~ 3 deg wide instead of 1.5)

What's missing from the above, ie. does not affect the search speed?

1. Any mention of the TDC
2. Any mention of the altitude indicator bars

Also, note that TWS has a fixed scan time of 2.2 sec for all submodes except high data-rate TWS which is 1.1 seconds ... all that is not represented in the FC3 eagle.

But to conclude, given the above parameters, the search volume speed is always constant for a chosen combination of mode, bars, azimuth and VSD range settings.   Moving the TDC has zero effect on any of this.

4 hours ago, Nahen said:

If we know what height the enemy is at, we lower the TDC down the radar screen and then by adjusting the elevation of the antenna (not by moving the TDC cursor) we move the narrowed scanning range, which is searched much faster by the radar. As a result - we shorten the time to detect the target.

None of that is correct, see above.

I refer both you @Nahen and especially @skypickle to the resource that @draconus posted:  https://tawdcs.org/radar-f15/

Go there, use the daylights out of it and understand how the radar works.

[Exorcet]

2 hours ago, draconus said:

What were you trying to show?

A lack of understanding of trigonometry and radars.

[skypickle]

thamk you all. Ironhand's videos were helpful. But I dont understand why the altitude numbers in the left margin change as I move the TDC? Moving the TDC does not change the angle or direction of the radar sweep.  Is it a filter to exclude radar echoes that return later than a specified time? Basically excluding radar echoes from further targets? If this is the case, then scanned wedge would be smaller in volume and the altitude numbers in the left margin would behave the way they do.

[GGTharos]

21 minutes ago, skypickle said:

thamk you all. Ironhand's videos were helpful. But I dont understand why the altitude numbers in the left margin change as I move the TDC? Moving the TDC does not change the angle or direction of the radar sweep.  Is it a filter to exclude radar echoes that return later than a specified time? Basically excluding radar echoes from further targets? If this is the case, then scanned wedge would be smaller in volume and the altitude numbers in the left margin would behave the way they do.

The volume a radar covers is a cone/wedge/slice of pie or  whatever similar shape works for you.  The further you are from the aircraft, the larger the size of the cone at that distance.  It's basically an angle translated to altitude, nothing more - it's just literally telling you 'the height of the cone at this distance is x, the low end is at x1 and high end at x2'.  Check out the site posted for understanding the radar and you'll get it.  It has nothing to do with filtering - it is literally the limits of the chosen antenna scan pattern.   The radar 'beam' is considered to be conical (or well, if you look at images of a radar/radio mainlobe, more like a really elongated water droplet) and as such you can simply consider it to 'open up' the further out it goes.

Edited April 4, 2023 by GGTharos

[Nahen]

Let me repeat once again - I am not speculating about the work of the AN/APG-63 radar - I am evaluating the work of the radar pseudo-simulation in the DCS computer game in the F-15C module.

Once you check how it actually works in the F-15C module in DCS and you won't talk about how it should work based on real radar, I'll come back to the discussion.

Oddly enough, 99% of the time I can "see" targets faster, farther than others flying this module.
The situation is exactly the same as choosing the size of the radar echo for rockets. Discussions that there is no, not possible, and yet it works in DCS...

If you think that the radars in the DCS modules work just like in real planes, then I congratulate you on your sense of happiness.

 

End of theme for me.

Edited April 4, 2023 by Nahen

[razo+r]

19 minutes ago, Nahen said:

Let me repeat once again - I am not speculating about the work of the AN/APG-63 radar - I am evaluating the work of the radar pseudo-simulation in the DCS computer game in the F-15C module.

Once you check how it actually works in the F-15C module in DCS and you won't talk about how it should work based on real radar, I'll come back to the discussion.

Oddly enough, 99% of the time I can "see" targets faster, farther than others flying this module.
The situation is exactly the same as choosing the size of the radar echo for rockets. Discussions that there is no, not possible, and yet it works in DCS...

If you think that the radars in the DCS modules work just like in real planes, then I congratulate you on your sense of happiness.

 

End of theme for me.

 

Your understanding is wrong and can be seen very easily. Here's an example:

Me, 5000ft, B-52 at 40'000ft 60 miles ahead of me.

Set elevation parameters in such a way that the target is visible on the scope.

 

Spoiler

 

As expected, I am able to detect the target.

Now I will move the TDC down and adjust the elevation so that the two indications contain 40'000ft. According to you, I should be able to detect it.

 

Spoiler

 

But since that's not how the radar works in the F-15C in DCS, I cannot detect the target.

If I use the exact same antenna elevation from the first picture while having the TDC at the exact same spot as above...

 

Spoiler

...oh look, the target can be detected, even if the target is at 40'000ft and the indicators indicate a different altitudes.

Edited April 4, 2023 by razo+r

[GGTharos]

5 hours ago, Nahen said:

Let me repeat once again - I am not speculating about the work of the AN/APG-63 radar - I am evaluating the work of the radar pseudo-simulation in the DCS computer game in the F-15C module.

The eagle radar is FC3 may be cut-rate compared to the real thing, but it still simulates a bar and azimuth setting, and paints targets according to that.

5 hours ago, Nahen said:

Oddly enough, 99% of the time I can "see" targets faster, farther than others flying this module.

I'd like to see proof of that statement  .   Show the work.  This shouldn't be hard - all you need is a stopwatch and do each method 10 times under identical conditions other than TDC placement.  If what you say it's true after all, this is a bug.

[Gilligan]

On 4/2/2023 at 12:01 PM, skypickle said:

I downloaded a fresh copy of dcs open beta. Deleted the saved games folder. Restarted the game , bound some controls for basic flight. Now, scan zone up and down work, but scan zone left and right do nothing still. Changing from TWS to RWS gives me a narrower scan angle but even in TWS, I cannot move the 'cone' of the scan volume left/right.

 

the radar already scans at max range left and right in RWS. Moving that scan zone will not change anything, just up and down. 

The cone will move left or right with the tdc slew in TWS. At least it appears to on the b scope.

Edited April 4, 2023 by Gilligan

[skypickle]

I dont know why you are all arguing. None of you have addressed the question: When you move the TDC, what is actually happening so that the altitude numbers on the left margin change? I am specifically talking about RWS. The only way I can imagine that the altitude range increases as you move the TDC upwards (further away from the aircraft) is that later and later returns are registered. Is this the case? 

[razo+r]

15 minutes ago, skypickle said:

I dont know why you are all arguing. None of you have addressed the question: When you move the TDC, what is actually happening so that the altitude numbers on the left margin change? I am specifically talking about RWS. The only way I can imagine that the altitude range increases as you move the TDC upwards (further away from the aircraft) is that later and later returns are registered. Is this the case? 

Several people have already answered this. 

The altitude numbers simply represent what altitude is being scanned at the distance of the TDC. 

[GGTharos]

I did address it.  It's just reading the dimensions of the cone at that distance, that is all.  It has nothing to do with timing or returns or anything like that.  Why would the altitude increase if the returns are 'later'?  I mean yes, these returns come later, hence they are shown as being further down range but that will happen no matter where the TDC is positioned. 

Go to the site posted, it makes everything clear.

Edited April 4, 2023 by GGTharos

[skypickle]

3 hours ago, GGTharos said:

I did address it.  It's just reading the dimensions of the cone at that distance, that is all.  It has nothing to do with timing or returns or anything like that.  Why would the altitude increase if the returns are 'later'?  I mean yes, these returns come later, hence they are shown as being further down range but that will happen no matter where the TDC is positioned. 

Go to the site posted, it makes everything clear.

 

you miss my point. HOW is it reading the dimensions of the cone at that distance? Are the altitudes in the left margin of the VSD calculations? or are they measurements? 

If they are measurements of the actual 'radar cone' then you need data to give you the horizontal distance for which you want to calculate the altitude.

The only way to get a measurement of horizontal distance is by timing a radar return.

The location of the TDC on the scope must therefore reflect how far away from your jet you are looking. But is that the result of measurement?

Edited April 5, 2023 by skypickle

[skypickle]

The other way to derive what is displayed as altitudes the VSD is simply to calculate the expected altitude of the triangle defined by the distance set by TDC cursor on the VSD. This would simply be a calculation and not a measurement.

Edited April 5, 2023 by skypickle

[GGTharos]

Ok, forget radar returns for this discussion, they're irrelevant.  In fact, everything but this is irrelevant:

Your radar has a beam width of x degrees which is fairly narrow, so it will scan several 'bars' in elevation ie. every sweep will more the antenna up a certain amount (let's say, one beamwidth) for each bar.

Knowing the bottom and top altitude of your scan pattern then becomes simple trigonometry, ie what is the the distance represented by a 1.5*4 ( 4 bars) angle at the distance of the TDC.  That's all there is - the center of the pattern is known because you've set it by manipulating your scan pattern elevation (we say antenna elevation but in reality it's the scan pattern).

 

PS:  Yes, it's just a calculation.

PPS:  Further returns aren't ignored.  If your VSD is calibrated to 160nm and the radar is calibrated to 'listen' up to 160nm, a strong enough return to be detected at range x>160nm will be displayed at x mod 160 range.  False returns ftw

PPPS:  But yes you can code each pulse train so in fact it can be ignored after a certain amount of time, you code the next train differently.

Edited April 5, 2023 by GGTharos

[skypickle]

thank you. That's all I really needed to know-where those numbers on the left side of the VSD come from.

[draconus]

Just one example to be sure. The Eagle flies here at 17.5k ft and its radar (in RWS mode) constantly scans the set yellow area by moving the antenna through a search pattern. The pilot freely moves the TDC around, it reads (approximated calculations) 13-22k ft altitude range at 10nm and 7-28k ft alt range at 22nm, but it won't change the radar scan area, its speed or the pattern. No matter where that TDC is, the radar will still illuminate that target for 39nm at 34k ft, it just won't show it when you have set VSD for the scan distance lower than 40nm.

Edited April 5, 2023 by draconus