[RESOLVED] F-14 RWR missile gives launch tone incorrectly

[Super Grover]

I mentioned the distances for a reason - the long distances of operation force the radars to be very powerful emitters.

I will give you an example using your -15db. As you calculated, it is 0.03. Now imagine that the law governing your device follows the inverse square of the distance from the emitter. Your device can detect the main lobe of the emitter from 100nm. At that distance, the -15db side lobe will be below your detection threshold.

Now, let's position your device at 15nm from the emitter, in the main lobe. The signal is (15/100)^-2= 44 times stronger than before. 44 times stronger than before means 16.5db. So when you move to the side lobe at 15nm, your received signal will be equal to 133% of the signal you received in the main lobe at 100nm. So certainly above the threshold. But you are in the side lobe at 15nm. Your device has no means to know if you are 100nm from the emitter in the main lobe (and maybe you are the target) or 15nm from the emitter in the sidelobe.

 

 

And that's only a small part of the full picture.

Edited March 30, 2019 by Super Grover

[Tomsk]

I mentioned the distances for a reason - the long distances of operation force the radars to be very powerful emitters.

I will give you an example using your -15db. As you calculated, it is 0.03. Now imagine that the law governing your device follows the inverse square of the distance from the emitter. Your device can detect the main lobe of the emitter from 100nm. At that distance, the -15db side lobe will be below your detection threshold.

Now, let's position your device at 15nm from the emitter, in the main lobe. The signal is (15/100)^-2= 44 times stronger than before. 44 times stronger than before means 16.5db. So when you move to the side lobe at 15nm, your received signal will be equal to 133% of the signal you received in the main lobe at 100nm. So certainly above the threshold. But you are in the side lobe at 15nm. Your device has no means to know if you are 100nm from the emitter in the main lobe (and maybe you are the target) or 15nm from the emitter in the sidelobe.

 

That makes sense, again using the wikipedia page for reference, if the first sidelobe is about 5 degrees off the main lobe. I wouldn't be surprised to be getting false indications in that scenario. It's close enough to the main lobe that it's going to be hard to tell.

 

However, I must confess I still don't see how that works for 30 degree angle off scenarios: assuming the wikipedia chart is roughly accurate. Let's say that 100nm main-lobe power is our threshold power (T); so taking your relative power formula:

P = (d/100)^-2
where
P is the power as a multiple of T.
d is the distance from the emitter.

 

We can then calculate the amount of power (Q) relative to T, that you'd get at a particular distance (d), on a sidelobe with a particular fraction (f) of side-lobe power relative to mainlobe power.

Q = f * P = f * (d/100)^-2

 

We can plug in our previous example, so 15nm out, sidelobe has 0.03 power of the main lobe:

Q = 0.03 * (15/100)^-2 = 1.333

 

This agrees with your answer. So then we can calculate the amount of power in the scenarios I posted: at 30 degrees off main lobe, which is roughly -30 decibels [seems I can't spell :)] less power according to the wikipedia chart, at 20nm from the emitter. So -30 decibels is an f value of 10^(-30/10) = 0.001.

Q = 0.001 * (20/100)^-2 = 0.025

i.e. just 2.5% of the threshold T (100nm main lobe) power. Indeed the distance where it becomes greater than T is around 3.16nm:

Q = 0.001 * (3.16/100)^-2 = 1.0014

 

So I'd have thought those scenarios should be well under the necessary threshold power. I'm sure you're right, you clearly have a great deal of expertise in this area, and I have no idea of the sidelobe power vs angle-off data you are using. But in any case thank you for indulging my curiosity a little :)

Edited March 30, 2019 by Tomsk

[Super Grover]

But you are aware that everything:

- the antenna radiation pattern,

- the threshold at 100 NM,

- the 15 NM distance

are just a made up example? And that I selected those numbers to match your -15db nicely?

[Tomsk]

But you are aware that everything:

- the antenna radiation pattern,

- the threshold at 100 NM,

- the 15 NM distance

are just a made up example? And that I selected those numbers to match your -15db nicely?

 

Sure, but maths is fun :) The 100 NM threshold seems vaguely plausible it shouldn't be a long way off that (within a factor of 3 or so I'd guess). The 15nm isn't really at all relevant. However, sadly the data I don't have to complete the picture is the radiation pattern. Your sim seems to be modelling a radiation pattern that is very different from the examples for directional antennas I've seen, but as I say not an expert on directional antennas :)

Edited March 30, 2019 by Tomsk

[Santi871]

And that's why we're preparing an update or a series of updates containing our custom beam properties modeling that I mentioned before.

 

Is this for all the radars ingame or just the tomcat's?

[Super Grover]

We plan to apply it to all SAM systems.

[riboyster]

Seems to be modeled correctly to me. Keep in mind that many SAM systems use radio command guidance on their missiles, so regardless of what angle a 3rd party is relative to SAM, they could in theory show launch indications if RC emissions are detected. IIR Sa2, 3, 4, 8 all use radio command guidance, while Sa 5 and more modern systems use passive reflection.

[riboyster]

This is exactly why you can turn the radar on for terminal guidance in sam simulator after letting the missile loose while tracking from memory.

[riboyster]

Or periodically turn on the radar if in a ARM filled environment to get a low on air time and minimize your likelihood of destruction; relying on the proxy fuse for detonation instead of radio command detonation.

[lucky-hendrix]

That's the world of the EM warfare. The RWR is not a crystal ball or a magical box that knows which missile carries a death wish with your name on it. And radar antennas are no lasers.

 

To detect a target, a radar has to emit quite significant energy in the form of an electromagnetic wave. The wave has to travel to the target, and then back to the radar antenna. It means that the signal that returns to the radar is much much weaker than the signal at the target - the signal that the RWR can receive. And that weaker signal must be still intensive enough for the SAM to detect the target. So the signal at the RWR, in a typical situation, is quite intensive even at longer distances. However, there are situations when the RWR can receive faint signatures from a lethal threat. So choosing which potentially lethal threat ignore and which keep is very difficult. And usually, it's better to be conservative and warn about more threats that aren't lethal than to miss that one missile that wants to hunt you down.

 

Add to that that no antenna is perfect, and it has multiple side lobes - and the RWR can't tell if a signal received comes from the main lobe or a side lobe. As Victory205 wrote, this is just scratching the surface.

 

Now let's return from those theoretical considerations to our DCS World. The good news is that we found a way to emulate the main/side lobe shape for the SAM threats using some fancy in-house developed techniques . Additionally, we added some additional custom corrections to the guidance signal strength which will improve the simulation at longer distances. Now it's as real as it gets.

 

Does it make the RWR more selective? At very long distances, it makes the situation a bit clearer. But the closer you are to a SAM, the more prone to fake launches the RWR becomes - and the result it's similar to the current state you have in the sim. Because the SAMs are just huge glowing electromagnetic lanterns.

I am impressed, the details you are modeling in this plane is unbelievable. You are real the top dev

 

Sent from my VTR-L09 using Tapatalk

[SDsc0rch]

is the plan for *all* a/c RWRs to behave this way?

or only heatblur's a/c??

[Super Grover]

I thought that I could mention another functionality of our RWR that some of you may be unaware of. In real life, the RWR uses a threat database containing different radar emitter signatures, the associated symbols that are displayed to the crew, but also defines which radar systems are friendly and which are used by the enemy.

In DCS, the selection of units available to both sides is often fictitious, so assuming that NATO/US aircraft/SAMs are always friendly, and Russian aircraft/SAMs are always the bad guys would be impractical. Instead, we decided to use per mission created threat databases, which are automatically generated when you enter the F-14. If a given type is only used on your side, the type is marked as "always friendly", and it's normally hidden from the display in the non-lethal and lethal rings. However, it will be still displayed in the critical ring (lock or launch warning). If you need to display all friendly emitters, the RIO can use the DISPLAY TYPE selector and switch it to FRIEND. http://www.heatblur.se/F-14Manual/cockpit.html#radar-warning-receiver-panel

This way, your RWR should be less cluttered from the harmless emitters.

 

However, when a type is present on both sides, all units of this type will appear on the RWR display - both friendly and hostile.

Edited April 1, 2019 by Super Grover

[SDsc0rch]

pretty smart