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RWR F-15C


Beamscanner

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1. When multiple Active air to air missiles launch on a F-15C, the victims RWR (TEWS) only shows that one missile from that direction has been launched. They are different missile seekers, operating on different frequencies. It should be apparent to the RWR.

 

2. All the radars sound exactly the same in this game.. (I don't expect you to have access to every radar sound, but you should at least use different fake sounds for each radar/mode)

 

3. The RWR signals do not get louder as you get closer to them..

 

4. Signals do not show up at all in the RWR, even if really close and really powerful, if they are not in the "field of view" of the RWR antennas. These "field of view" angles represent the top 3dB of the antennas main lobe, otherwise known as the Half Power Beamwidth (or beamwidth for short). Understanding this, we must recognize that the "beamwidth" does not account for the signal gain beyond these angles. As such, people not familiar with antenna theory may assume the beamwidth represents the entire area capable of receiving signals, and that beyond this point the gain drops off completely. (- infinity dB)

 

The F-15 uses a set of archimedean spiral antennas, spiral antennas are known for their ultra wide bandwidth(30:1 ratio) and are not very directional (~half hemisphere). These types of antennas have a "beamwidth" (or half power beam width / only counting the top 3dB) of 65 degrees @ 9GHz on the azimuth plane. However, the 10dB "beamwidth" (only counting the top 10dB) extends all the way to 127 degrees (and well beyond that for lower frequencies)

 

Below is the actual radiation pattern (in red) for the 2'' Model 53411 spiral antenna used on many US fighters, including the F-15C.

zhU6lC9.png?1

Above: I have overlaid the 3dB beamwidth (65 degrees wide) in blue, and the 10dB beamwidth (127 degrees wide) in green. As you can see, there is a gradual decline in gain across the axis, and certainly no distinct cutoff at the edge of the "beam width", which some would strictly consider the antennas "field of regard".

 

Below: Here you can see the same figures comparing the beamwidth across the frequency spectrum.

vOkDwCg.png?1

 

As you can see, its not so black and white. An extremely weak signal off in the distance may only come in if its directly boresight of one of my antennas. Conversely, and more importantly, a powerful signal that's really close (like say from a missile seeker) should be able to be seen well outside of the advertised 3dB beamwidth of 65 degrees in azimuth. (and certainly outside of those angles in elevation, which is considerably wider based on the documentation.

 

I haven't even mentioned the fact that powerful signals will bounce all over and into your air-frame and re-emit from conductive objects with a matched resonating frequency. Eventually, making their way into the RWR antennas if they weren't already in it's beamwidth.

 

TL/DR:

I should be able to see close AI radars and Missile seekers that are locked on to me, even if I'm in a sharp bank. An active missile should not be able to strike me from directly below and without making a squeak on my RWR.:lol:

 

Sources:

[ame]http://www2.l-3com.com/randtron/img/53411_2in_Spiral.pdf[/ame]

http://www.antenna-theory.com/antennas/travelling/spiral.php

53411_2in_Spiral.pdf

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This was a great read thank you! :thumbup:

 

Fidelity of this magnitude would be something that we could expect from a DCS level F-15C, there is a great deal of functionality missing from several systems on the FC3 F15C as you will have noticed.

 

FC3 aircraft are a compromise with regards to the avionics and sensor systems on the aircraft, it has been stated before that FC3 aircraft are more or less done in terms of their functionality system wise.

 

I wouldn't expect much more capability to be added to the TEWS however I will forward this on to the devs as a request to see if something could be possible, but my money would be with having to wait for a DCS level Eagle for this kind of modeling.

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  • 6 years later...

Really great post.

Are there however not ways in post processing you can use to get better directional info. I.e. phase comparison of signals between antennas. 

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  • 1 month later...

mig-21 pilots have reported that the eagle's radar was so powerful that it saturated their RWR systems such that it gave a 360-deg indication (ie: the system indicated the eagle's radar was ALL AROUND THEM - the whole thing lit up!)

@Beamscanner's post makes sense 

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