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Questions about the radar


flo57100
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Hi guys,

 

I discovered more and more the Viggen the last days, and I really LOVE it !

 

But I have questions about the radar:

 

- How does the radar ground avoidance mod work ? I out the radar in M2 mode, I have the sweep with the terrain in front displayed on the scope, then I press the switch to go in ground avoidance mod, and then I hav a white-greenish display with sometimes a black line there or there, but I have no idea how to interpret those informations

 

- What is the Linear/Logarithmic switch made for ? It's behind the radar stick, on the left console. I saw it changes the display from white-greenish background to a blackish background, but what is the purpose for each mode ?

 

- Finally, what is the purpose of the radar M3 mode, the mode which gives us a square-shaped display on the scope ?

 

Thank you very much for people who may enlight me on those points, now I'm quite puzzled with those

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- How does the radar ground avoidance mod work ?

 

It's a little difficult to describe, maybe someone will be able to describe it better but the way I see it is as if you were to take a slice out of a mountain, it'll show you that slice in black. The easiest way to start seeing it this way is to fly through valleys. It's not super useful just for flying over hilly terrain imo, but rather flying through relatively wide valleys in the dark. The black will represent a slice of the sides of the cliff, and the green in the middle will be the valley through which you can pass.

 

- What is the Linear/Logarithmic switch made for ?

See page 112 of the manual for more info, but roughly, Log (default) is good for making out targets on the ground, in mixed terrain, and Lin is better to sharply make out terrain features. Both amplification modes can be adjusted using the MKR knob.

 

- Finally, what is the purpose of the radar M3 mode ... ?

The manual says it gives you a close-up of an area on the radar for making out details more clearly, but exactly what area it is or how you adjust it I have never been able to determine. Perhaps it's a work-in-progress feature, or maybe someone else will chime in.

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- How does the radar ground avoidance mod work ?

First, the radar antenna is lifted to about 0° degrees (looking straight forward) instead of being pointed downwards to the ground. A radar sends out waves. When the wave hits something it may return and the radar picks that up. It can measure the distance to the point where the wave hit something by knowing the time it traveled and the speed of the wave. When the wave does not hit something, it does not return.

The radar of the Viggen displays this with color. Green means, wave did not return. Black means, wave did return pretty quick. Something which is between black and green would be an object at a middle distance, black is pretty near and green is far away.

So when flying in this mode, black means there is a blocking terrain in front of you in the indicated direction. Green means - it's safe to fly here, no blocking object in that direction.

 

HZq31O4.jpg

 

EaXYaOC.jpg

 

I4mq9Cu.jpg

 

- What is the Linear/Logarithmic switch made for ?

Recall the graph of x and the graph of log(x). The log-graph has an extreme gradient in the first steps and then slowly grows. The linear-graph has the same gradient from left to right.

If you use the linear gradient, you will get a true feedback of distance to color. Let's say total green means 20km and black means 0km. Then an object at 10km will be half green, half black mixed. If you use the logarithmic scale everything further than 10km will already be full green. While in the range where the gradient is big, stuff which is close together will have a relatively huge color difference as the gradient is bigger than in linear-scale.

The advantage of the logarithmic setup is that it will display the ground in a different color than a vehicle which is only 2m higher than the ground. It amplifies the color difference between those objects though they are close together.

 

AfsANgP.jpg

 

g19s3jk.jpg

 

- Finally, what is the purpose of the radar M3 mode, the mode which gives us a square-shaped display on the scope ?

This mode changes the style of how the radar screen displays its information to you. Normally you would have a view like this at the radar screen:

 

PaKZhWi.jpg

 

The colors indicate different radar waves. The screen displays the waves exactly in the style they are emitted. A wave that gets emitted 45° to the top right, will also display its corresponding distance at that point in the screen.

In the B-Scope mode however, the center point which indicates your aircraft will no longer be a point - it will be the total lower bound.

The same waves than seen in the image before, will now display their feedback as this in the screen:

 

2oCQb9Y.jpg

 

So the waves get emitted the same as before but they will display their information at other points in the screen.


Edited by Zabuza
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The manual says it gives you a close-up of an area on the radar for making out details more clearly, but exactly what area it is or how you adjust it I have never been able to determine. Perhaps it's a work-in-progress feature, or maybe someone else will chime in.

 

It zooms in around the currently selected waypoint except in A2A mode / Ground avoidance mode where it shows what's immediately ahead (1->10 km or something like that, can't remember exact number)

/Daniel

 

Heatblur Simulations

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This mode activates only the RWR. So you are able to pickup other radar frequencies or units with activated jammer but don't emit radar waves by yourself.

 

It is also used for the reconnaissance modes of the Viggen. As it is able to compute the position of other radar emitters by picking up their direction from different angles of your own aircraft.

 

They talked about that here:

https://forums.eagle.ru/showthread.php?t=182428

 

If you don't emit radar waves by yourself, you have the advantage that you don't show up on enemies RWR systems. So you can receive their radar signals but they won't see you coming.


Edited by Zabuza
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Doesn't the passive scan mode also show waypoint circles? (I'm away from my sim PC ATM so I cannot check)

Yes it does. One thing I realized today (and quite a 'duh' moment it was), if you try actively looking for stuff on the radar, turn off Passive Radar, else the radar scope doesn't show much. It will be all green instead of coastlines etc, and radar returns from ships become really hard to see. >_<

 

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Sounds obvious to me. If the radar is in passive mode, it does not emit any waves - it is not active.

Thus the radar screen is blank. It gets the information from the waves which only get emitted in active mode - that's why it's called active mode.

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No, it's the other way around. The screen is all lit and shows dark vectors to there it receives incoming radiation.

 

Sent from my Nexus 5 using Tapatalk

ASUS Z170-P w/ Intel i7-7700, 32GB DDR4 RAM, SSDs out the wazoo and a GTX 1080Ti,

Oculus Rift CV1, TM Warthog stick and throttle, TM Cougar MFDs, MFG Crosswind pedals and WheelStandPro Warthog (w/ the custom small Warthog plate)

 

Former F-16 Ground Crew @ RNoAF

[sIGPIC][/sIGPIC]

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First, the radar antenna is lifted to about 0° degrees (looking straight forward) instead of being pointed downwards to the ground. A radar sends out waves. When the wave hits something it may return and the radar picks that up. It can measure the distance to the point where the wave hit something by knowing the time it traveled and the speed of the wave. When the wave does not hit something, it does not return.

The radar of the Viggen displays this with color. Green means, wave did not return. Black means, wave did return pretty quick. Something which is between black and green would be an object at a middle distance, black is pretty near and green is far away.

So when flying in this mode, black means there is a blocking terrain in front of you in the indicated direction. Green means - it's safe to fly here, no blocking object in that direction.

 

HZq31O4.jpg

 

EaXYaOC.jpg

 

I4mq9Cu.jpg

 

 

Recall the graph of x and the graph of log(x). The log-graph has an extreme gradient in the first steps and then slowly grows. The linear-graph has the same gradient from left to right.

If you use the linear gradient, you will get a true feedback of distance to color. Let's say total green means 20km and black means 0km. Then an object at 10km will be half green, half black mixed. If you use the logarithmic scale everything further than 10km will already be full green. While in the range where the gradient is big, stuff which is close together will have a relatively huge color difference as the gradient is bigger than in linear-scale.

The advantage of the logarithmic setup is that it will display the ground in a different color than a vehicle which is only 2m higher than the ground. It amplifies the color difference between those objects though they are close together.

 

AfsANgP.jpg

 

g19s3jk.jpg

 

 

This mode changes the style of how the radar screen displays its information to you. Normally you would have a view like this at the radar screen:

 

PaKZhWi.jpg

 

The colors indicate different radar waves. The screen displays the waves exactly in the style they are emitted. A wave that gets emitted 45° to the top right, will also display its corresponding distance at that point in the screen.

In the B-Scope mode however, the center point which indicates your aircraft will no longer be a point - it will be the total lower bound.

The same waves than seen in the image before, will now display their feedback as this in the screen:

 

2oCQb9Y.jpg

 

So the waves get emitted the same as before but they will display their information at other points in the screen.

This is a good and pedagogical explanation, but it unfortunately gets a fundamental point wrong. In practical terms it's fine and the advice is functionally correct, but I am the king of nerd trivia and will not stand for misunderstandings of the underlying technology ;V

 

The color has nothing to do with the range. The range is translated into position on the screen. The very bottom of the screen (where the sweep originates) is the position your aircraft, and "further away" is up. How far away the top edge of the screen is, is determined by the range setting (number in km shown in red in the lower right corner of the screen). The color on the display is the strength of the radar return (as in, how much energy we got back) - no return is green, as you say, and a strong return is black. How strong the return is depends on a multitude of factors, but most importantly what material the lobe is bouncing against and its angle relative to the lobe. The reason the black returns in obstacle detection mode aren't just thin lines is that the antenna lobe has a height, so a thin line means a vertical cliff face (entire lobe returns from the same distance) and a broad band means a slope (lower parts of the lobe return before the upper parts or vice versa). Th Viggen's radar is a monopulse design that uses lobe shaping, so exactly defining the size of the lobe is tricky, but if I understand the diagrams in the SFI right, obstacle detection mode has a lobe that's about +/- 6 degrees in width (in other words, 6 degrees to each side of where the antenna is actually pointing) and 2-3 degrees in height. In map drawing mode, the lobe is shaped the other way (wide in height, narrow in width), which the SFI claims gives a more nuanced map image (I'll take their word for it... :V).

 

It is obviously true though that the strength of a radar return decreases with distance (the radar equation tells us so), so you'd think that you would be right anyway. However, the Viggen's radar has a "controlled damping" function (really no idea how to translate that, "styrd dämpning" in Swedish) that compensates for signal strength dropoff over range, so a given target with a given RCS will always be displayed with the same intensity regardless of range. In obstacle detection mode this is always active, but in some modes (including map mode) you can turn it off with the AS knob (mode 0 does not always disable it; try mode 3, 4, 5 or 6, but I'm not sure if any of those actually work in DCS).

 

Passive mode on the radar has nothing to do with the RWR, by the way. It just does everything the radar normally does except actually transmitting. The only things you can see on the radar screen in passive mode (other than symbols? don't remember if those are drawn, but they definitely can be, they're drawn with a different ray gun than the regular sweep) are jammers that are either specifically targeted at your radar or transmitting broadband noise. The radar does not gain any extra receiving powers or signal processing abilities in passive mode, so you won't see things like, say, air search radars that operate on a different frequency.


Edited by renhanxue
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Passive mode on the radar has nothing to do with the RWR, by the way. It just does everything the radar normally does except actually transmitting. The only thing you can see on the radar screen in passive mode (other than symbols? don't remember if those are drawn, but they definitely can be, they're drawn with a different ray gun than the regular sweep) is jamming that is specifically targeted at your radar (or jammers that are just sending broadband noise). The radar does not gain any extra receiving powers or signal processing abilities in passive mode, so you won't see things like, say, air search radars that operate on a different frequency.

 

I was doing the blockade runner mission earlier, and I'm fairly sure the passive radar mode showed me the general direction of the ship using some kind of constant (targeting?) radar energy, but it didn't pick up on search radar energy. Then again, I could be confusing things together here (it could be the ship was jamming me too, I don't know how ships work, especially in DCS).

 

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Oculus Rift CV1, TM Warthog stick and throttle, TM Cougar MFDs, MFG Crosswind pedals and WheelStandPro Warthog (w/ the custom small Warthog plate)

 

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Cool!

 

Sent from my Nexus 5 using Tapatalk

ASUS Z170-P w/ Intel i7-7700, 32GB DDR4 RAM, SSDs out the wazoo and a GTX 1080Ti,

Oculus Rift CV1, TM Warthog stick and throttle, TM Cougar MFDs, MFG Crosswind pedals and WheelStandPro Warthog (w/ the custom small Warthog plate)

 

Former F-16 Ground Crew @ RNoAF

[sIGPIC][/sIGPIC]

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No, it's the other way around. The screen is all lit and shows dark vectors to there it receives incoming radiation.

 

Sent from my Nexus 5 using Tapatalk

 

That's what he's saying. On the Viggen radar screen green=no returns (blank) so if it's in passive mode since it doesn't emit any signals itself only signals from other emitters will be shown so obviously you will be unable to discern any ground details. :-)

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RoT: Aim for the white space, note the black lines encircling your white space! It's not great, I can't say that I could use it in zero visibility, but one day for a laugh I might. It might be good for using during penetrating cloud cover from above as an additional safety net, I don't trust the red light much!

 

Note it's also good for telling you that you are hidden beneath terrain for radar masking purposes to the front of you.

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That's what he's saying. On the Viggen radar screen green=no returns (blank) so if it's in passive mode since it doesn't emit any signals itself only signals from other emitters will be shown so obviously you will be unable to discern any ground details. :-)

 

Ah, yes, now I see what you're saying. My bad!

 

Sent from my Nexus 5 using Tapatalk

ASUS Z170-P w/ Intel i7-7700, 32GB DDR4 RAM, SSDs out the wazoo and a GTX 1080Ti,

Oculus Rift CV1, TM Warthog stick and throttle, TM Cougar MFDs, MFG Crosswind pedals and WheelStandPro Warthog (w/ the custom small Warthog plate)

 

Former F-16 Ground Crew @ RNoAF

[sIGPIC][/sIGPIC]

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