A/G radar picture

[brettt777]

Okay, so at about 12:05 on the following YT link, we see the AN/APG-70 in A/G, RBM mode, at 40 mile range and at altitude, and we see that the ground returns are basically just a narrow band across part of the sweep. This band of ground returns depends on the selected range, the aircraft altitude, and the radar antenna elevation.

 

Okay, fine. Here is another link of the FA-18C AN/APG-73 radar in A/G mode in a similar setup; at altitude and at 40 mile range.

https://www.youtube.com/watch?v=VULxns6OkF4

As you can see, there are ground returns over the entire range of the PPI display. Obviously the amount of returns still depends on the range, altitude and antenna elevation but there are still returns over the entire range. Here's another link of the AN/APG-68 radar from the F-16C in A/G mode at 80 mile range. At 2:38, you can see ground returns over the entire 80 mile range.

https://www.youtube.com/watch?v=t3uAuYijeug

And finally, here is the KLJ-7 radar in the JF-17, once again in A/G mode and at altitude and at 40 mile range. And once again, we see ground returns throughout pretty much the entire PPI display, even at short range.

https://www.youtube.com/watch?v=kMSExqW9p6s

Even the older AN/APG-120 radar in the F-4E Phantom had ground returns pretty much throughout the range of the scope...

https://www.youtube.com/watch?v=x5oJUPPo8zQ

Then we have the afore mentioned A/G radar in the F-15E, which only has the narrow band of ground returns. Then here are two links for the RDI radar in the M2000C Mirage III and the CYRANO IV radar in the F-1 Mirage, both in A/G mode at altitude and longer range. Like the F-15 A/G radar, the A/G radars in both versions of the Mirage have a somewhat narrow band of ground returns on the A/G display, depending on the range and altitude, and antenna elevation.

https://www.youtube.com/watch?v=W4USr2u1O2w&t=1442s

https://www.youtube.com/watch?v=WrE5-yV2igc&t=35s

So my question here I think is obvious. Why do some A/G radars show returns through the entire range of the display and some only have a narrow band of rturns, especially at altitude? Now, I am a retired aviation maintenance tech that specialized in avionics. I spent most of the last four decades installing and maintaining both military and civilian avionics including radar, so I very much know how a radar works. The aircraft I worked on in the US navy had a basic search radar but it was still a good radar cuz it was basically a stripped down version of the AN/APQ-148 bombing/fire control radar out of the A-6E Intruder. That being said, I never got to see the radar actually working in a long range, high altitude setting. The most I ever got to see was pointing the nose of the aircraft off the bow of the carrier and seeing a few ships and possible a coastline or some inland mountains. So what is the deal? Why the difference? I thought maybe it was the age of the radar system. Something with the design of the antenna array with the older systems caused it to receive only a narrow band of ground returns. But the AN/APG-120 is probably the oldest of all those systems and yet it isn't that much of an issue. So is this an accurate representation of the real thing? Are the A/G radars in the F-16, FA-18 and JF-17 just that much better than the F-15E radar? I would think that as good as the F-15's AN/APG-70 is with the HRM that it would also have an exceptional RBM picture even at long range and altitude like the Hornet or the Viper. But I went on a long nav flight around Sinai in the F-15E last night and honestly the RBM A/G radar picture was... not too impressive. Are they supposed to work this way or did some of the devs just get their radars wrong?

[draconus]

Idk about other aircraft but RBM in F-15E uses a single bar azimuth sweeps and that's what is shown on the scope as a result correctly.

Others can have different display method, different mode or are just wrongly modeled. If it's MSA radar (and they all are) it has to have a narrow beam moving laterally and just can't scan the whole elevation with one sweep or I am missing something.