What RCS/etc is the radar range circle based on?

[NimrodX]

Is the range circle for radar based on a particular radar cross section value like 1m2/0dBms?

By that I mean, assuming ideal conditions and no jamming, should a radar with a given range circle be able to detect a target with an RCS of some minimum like 1m3 once it enters the circle?

If not, what's the range circle for a radar based on?

[rmunie0613]

I believe that the range circle, as it is for weapons also, is its "maximum range"... against low RCS/"stealth" units it will not detect at max range.

[NimrodX]

Ok, but does this mean that the range is just hard coded from a specification like "this radar will absolutely never detect anything beyond 50nmi. But within that range the reflected power formula will be used to determine detection." And the range circle is just based on a hard "max range" spec?

[User2]

"This radar will absolutely never detect anything beyond its max range"
Yes.
That's how real radar works. Sends a signal at a given direction and waits for a reflected impulse. The time the radar is willing to wait for a return determines the maximum possible range.

[NimrodX]

Ok, so Sharana says the max range is usually set at whatever has an 80% chance of detecting a 1m2 RCS target. So this must be the cutoff point for not wanting to waste any more time waiting on an echo and thus slowing down the sweep etc.

[rmunie0613]

A great deal of playing and experimenting, as well as some "real world" understanding of several of the systems... leads me to think that the max-range circle in game is more of a max-range against a larger (than 1m2 RCS) target... the best way to check it though really is to experiment...put in a radar, put in a few different RCS platforms, and switch to the radar side to see when it detects. In my experience thus far, many of the "stealth" type platforms can get nearly halfway through the "range circle" before being spotted...not "every time" to be sure, but a solid 50-60% of the time...while of course non-stealth aircraft usually are detected (in my own experience...) very near the range limit.

[Sharana]

ORIGINAL: rmunie0613
while of course non-stealth aircraft usually are detected (in my own experience...) very near the range limit.

Well all non stealts have 1m2 RCS or bigger while the stealts ones are 0.0... something.

[rmunie0613]

Yes, correct But the 1 sq.m. (something like the AH-1 Cobra which is listed as 1.1) has nearly always been able (again, in my own observation only) to get WELL inside of the "max range" displayed. Because of that, I have usually counted on that range being against something like an Airbus, and making other contingency plans for smaller aircraft to be sighted.

[Sharana]

ORIGINAL: rmunie0613

Yes, correct But the 1 sq.m. (something like the AH-1 Cobra which is listed as 1.1) has nearly always been able (again, in my own observation only) to get WELL inside of the "max range" displayed. Because of that, I have usually counted on that range being against something like an Airbus, and making other contingency plans for smaller aircraft to be sighted.

You probably forgot you need clear line of sight. Earth is not flat as some might think, there are mountains etc. If that chopper is flying as high as Airbus to avoid those line of sight problems there shouldn't be problems with detection, but choppers aren't That's why non low observable planes penetrate air defenses with low level flying - radars just can't see through earth or mountains to spot them from far away.

[NimrodX]

Yea, try a radar on top of a mountain an a 1m2 helicopter flying at max altitude. I bet anything semi-modern will detect it.

Helicopters also have this issue where the rotor advances and retreats at 300+kts or something which as you might imagine creates quite the doppler phenomenon. Modern radars are designed to look for this signal pattern. That's particularly useful if they're hovering since without it they'd generate no doppler shift corresponding to displacement. No doppler shift means no radar lock and a higher chance of rejecting the signal as spurious.