b.t.w., is the AL-31FM1 on Rusoboro export list?

As far as i remember no. Only the F, FP and FN that being offered.

if rad base didnt factor in surface wave diffraction then RCS at 1 Ghz would be lower than 10 Ghz , which is clearly not what they showed in their simlation

It is lower and the “beamwidth” become broader. Don’t you noticed it ? Please look again at your Graph. Look at the “Blue” Line (1 Ghz) Thus why when the first time i saw that graph i concluded that the software only calculate specular RCS but later from the technical brochure i found it’s also do Multiple edge scattering and Edge diffraction.

The edge diffraction one however is the one i doubt that it will include surface wave and creeping wave.

Well, you should ignore those people:

http://kret.com/en/news/3527/

I don’t mean to be rude, but it’s very difficult to *debate* with someone when the very foundations of their argument are often proved factually incorrect and are sometimes nonsensical.

still wondering though.. why they can’t just install it in the main array.

(Already browsed the older thread but some points doesn’t make sense to me, especially the whole “IFF tracking” stuff)

Hello all :3 quick question.

Why S-300F..or early variant of it use 3R41 Volna ?

Unlike its land S-300P sisters. Volna is a reflective type ESA where the feed horn is placed at the front of the antenna. Im also see similar trend at Klinok and Orekh. Why those systems don’t use (except at Peter the Great where it has a 30N6 replacing one of 3R41) Backplane feed as its land based system ?

More like another Chinese animation studio showcasing their 3D skills. Which is awesome.

No need to take it seriously.

that probably due to the fact that reflection from surface wave is much lower than from spectacular return, thus they beng overlapped in the graph

Or it’s not considered. Found the rad base brochure here :

It’s simulation includes

· Blocking
· Multiple Bounce Interaction
· Edge Diffraction
· Polarization
· Dielectric Materials
· Bistatic Computations

https://www.scribd.com/doc/278284451/RadBase2-Tech-Paper

They also use Chu Stratton integral method which can be used to measure diffraction from surface wave

Then i wonder why their polar plot somewhat only depicts Specular RCS result.

Let’s try computational electromagnetic simulation of an F-22, shall we?……….’oh oh spaghettios’!!:

https://www.google.co.jp/url?sa=t&source=web&rct=j&url=http://www.ijrame.com/vol2issue1/V2i105.pdf&ved=0CB8QFjAAahUKEwjfnubq59vHAhVEPhQKHTTlDeU&usg=AFQjCNGlPzhSPjv-SAVP3qsUUTChB4OvGg&sig2=3ptES2xxLChWF76-OhN5vQ

The most interesting aspect in that paper, for me at least is NOT their RCS measurement but their derivation of radar range equation. One can actually find out its detection range in various band if having a “reference range” It’s basically 4th root law but using frequency.

It basically state that VHF Band radar will have 7-8 times detection range of X-band (assuming same gain etc..Only frequency change) L-band will have 2 times detection range compared to X-band.

How to use calculate that ? The paper doesn’t mentioned it but i figured out myself.

Reference band : 10 GHz =10000000000 Hz
Reference range :30 Km

We want to calculate range at VHF Band (175 GHz). We need to find the detection range “factor” of the reference band first

range factor for 10GHz : SQRT(1/10000000000)

Range factor would be : 0,00001

Then we find range factor for the VHF band

0.175 GHz = 175000000 Hz

range factor for VHF : SQRT(1/175000000)

Range factor would be : 0,0000756

Then divide the range factor of the band we intend to calculate with reference range factor :

0,0000756/0,00001 = 7.6

Thus the 175 MHz radar will have 7.6 times range of the X-band radar or 7.6 * 30 = 226.8 Km.

I’ll have to find the original source, but here is a graphic from a university study. Keep in mind that no RAM was used and only shape was considered. It’s also a generic airframe that conforms to normal VLO design precepts (no right angles, continuous curves, etc).

Note that the differences between 1Ghz (UHF/L Band) and 12Ghz Ku Band) are not that great.

Would love to see the paper.

From what i see however.. That RCS polar plot only consider specular RCS spikes. While low band radar’s “counter stealth” mechanism relies more on resonance and creeping wave. Those two mechanism that will add RCS.

Specular RCS from what i know kinda behave like “antenna beamwidth”. Having similar “wavelength/antenna dimension” relation. The larger the wavelength the weaker the lobe BUT it’s getting broader. While smaller wavelength will produce a very sharp and strong but narrow lobe accompanied by weaker “sidelobes”