VHF radars are overhyped. even if they detect F-35 they can't provide enough targeting data to X-Band fire control radars of SAMs & Fighter Aircrafts.
why you think those sam need their x-band radar to engage incoming target
"why not build every radar for lower bands? Because they are less accurate at lower frequencies"
From the article i attached.
Here is the reason why the need for different bands for the same problem: detection and tracking. But first, this is real physics. Not 'Russian physics' or 'Chinese physics' or 'Iranian physics'.
Now, here is a typical radar pulse...
1. On each pulse, we have a 'leading edge' (LE) and a 'trailing edge' (TE). We can look at each pulse as a packet of energy. The transmitter start, then after one sec (example), the transmitter stop. That is one pulse. This understanding is foundational and critical for everything that is of radar detection.
2. The larger the packet of energy, the more durable it is from attenuation (loss) as it travels thru the atmosphere. Conversely, the smaller the pulse, the less durable. We must understand that as the pulse travels, it literally collides with all sorts of particles and molecules in the atmosphere, and each collision is an energy loss -- attenuation. Rain, fog, mist, and snow droplets weakens the pulse to the point of nothing left at all. This is why weather is
GENERALLY bad for most radars. Not all, just most.
3. The LE and TE are critical in
TIMING calculations of the target. Each echo or return or reflection has the same LE and TE as the transmitted signal. The transmitting part remembers pulse characteristics, then the receiving part reference that to process the reflections.
Now we add 1 thru 3.
These are critical target resolutions:
1. Altitude
2. Speed
3. Heading
4. Aspect angle
The longer the distance of detection, the more energy per pulse is needed. But this would spread out the LE and TE, making timing coarser and coarser, affecting precision and accuracy of all target resolutions.
We can use a real life analogy -- your eyes.
If you open and close your eyes, you have effectively simulated a pulse train. The longer you keep your eyes closed, the less you notice how the car changed its position. So if you open/close your eyes rapidly, you will be able to process the car's movement with more precision and accuracy.
If we make the pulse LE and TE shorter and shorter, there will be less energy per pulse, making the pulses more vulnerable to travel losses -- attenuation.
So when we add 1 thru 3, we can see why there is a need for various bands for different situations. We do not need to use military situations, just a regular airport air traffic management will do.
If we want to detect airplanes 100 km out, we need to use lower freqs with longer pulses with higher levels of energy. At 100 km out, we just need to know their approximate locations. We just need to know how each airplane change its position every 10 secs, for example.
But at 50 km or less distance, we switch to higher freqs with shorter and shorter pulses to more fine grain processing of their target resolutions. We need to know how each airplane moved every second, for example, so that we can line up their landings safely and efficiently.
Then at 10 km distance, we switch to even higher freqs with even shorter pulses to know how each airplane move every 1/10th sec, for example. Because now, we are monitoring the actual take-off and landing of many airplanes all over the area. We are working within visual range so even though the pulses are weaker in energy, their short LE-TE give us closer and closer timing calculations, which is critical.
Now, change from airport to air defense. We need an array using low freqs with long pulses to detect several hundreds km out. Then we use another array using higher freqs with shorter pulses to detect fast incoming attackers. In principle, there is no difference between managing an airport to prioritizing air defense needs. The radar application is still the same.
Low radar observable bodies are designed to affect the higher freqs with short pulses. That is why 'stealth' are dangerous because the attacker gets closer and closer before enough of those X-band pulses can produce enough reflections with enough energy to process those four target resolutions. We cannot use low freqs with short pulses because of the physics of the pulse creation because there has to be a certain separation between the LE and the TE in order to have a coherent pulse in the first place. In other words, imagine the LE and TE as a container or bucket. There has to be a minimum size bucket in order to hold a certain amount of energy.
The next reason why we cannot use low freqs is because of pulse characteristics.
We can create pulses with different characters as illustrate above to process those four target resolutions to even finer levels. Low freqs are not as easily to process as higher freqs. So we have to go back to having multiple arrays using multiple freqs just to process one target. And the 'stealth' target is not making that any easier.
