Radar Beamwidth

[Neor]

Hi, the Radar is not using the right Beamwidth of 3.3° https://forums.eagle.ru/showthread.php?t=192382

 

One Example

 

I have used the numbers from one of Wags videos. (picture)

 

converting in meters

hight of the plane 19620 ft > 5980 m

distance of cursor 73,2 nm > 135566 m

beam 3,3° x 4 > 13,2° (4-bar scan)

 

Radar Cursor

50k ft > 15240 m

-11k ft > -3353 m

 

now i have used the numbers in CAD (because im lazy :lol: )

 

and the result is a 7.8° scan instead of 13.2° (in a 4-bar scan for this example)

 

Numbers are divided by 100 for better handling in CAD

[Manuel_108]

So, basically the radar scan volume should cover almost twice the height it does now?

[Neor]

We have to wait for the response...

[hornblower793]

Is the beamwidth you have used for azimuth or elevation? (not clear from the posting you have referenced) - about 20 years since I have modelled any radar systems so I am very rusty

Edited April 11, 2019 by hornblower793

[Neor]

The radar sends the signal like a cone if I'm understanding it right. This cone should have a 3.3° diameter dashed circle.

its the same cone like when Boresight (BST) acquisition sub-mode is selected.

[Cp]

Ive got no idea how the real radar works or should work, so im just guessing here; maybe each bar overlaps slightly thus resulting in a smaller volume. What happens if you do a 1 bar search and run the same calculations?

[prof_laser]

I remember setting radar to 1 bar puts the upper and lower limit to the same value (probably not correct). But if what Cp said is true, then using 2 bars should NOT result in half the covered altitude from 4 bars, since it then has only 1 overlap instead of 3.

[Neor]

if you do a one bar scan and same distance, the courser should show 50 high and 24 low

2-bar > 50 high -1 low

4-bar > 50 high -53 low

Edited April 11, 2019 by Neor

[hornblower793]

Having had a quick look around the Internet I have found other sites stating that the vertical beam width is about 2 degrees. Below extracted from http://vnfa2.tripod.com/FA-18_Radar.html

 

 

• Antenna Elevation - Vertical (height) scan of the radar antenna based on the number of bars selected. One bar is equal to about 2° of vertical scan. As you add more bars (up to 6-bars in F/A-18 Hornet), you add an additional 2° per bar, up to 12° of vertical scan volume. The figure below depicts a 4-bar scan.
  

Cannot comment on whether this information is accurate but it agrees with the figure you have calculated

Edited April 11, 2019 by hornblower793

[drPhibes]

Just as a note, beamwidth typically refers to the half power (-3dB) width of the main lobe. The lobe extends beyond this. Exactly how much depends on the antenna design.

 

 

 

Here's an illustration that shows the principle:

 

[Neor]

Having had a quick look around the Internet I have found other site stating that the vertical beam width is about 2 degrees. Below extracted from http://vnfa2.tripod.com/FA-18_Radar.html

 

 

• Antenna Elevation - Vertical (height) scan of the radar antenna based on the number of bars selected. One bar is equal to about 2° of vertical scan. As you add more bars (up to 6-bars in F/A-18 Hornet), you add an additional 2° per bar, up to 12° of vertical scan volume. The figure below depicts a 4-bar scan.
  

Cannot comment on whether this information is accurate but it agrees with the figure you have calculated

 

 

ok, that explains it very good.

if the 2° is true, then it makes totally sense.

and it also means, there is some overlapping between the bars...

Edited April 12, 2019 by Neor

[Svend_Dellepude]

Just as a note, beamwidth typically refers to the half power (-3dB) width of the main lobe. The lobe extends beyond this. Exactly how much depends on the antenna design.

 

 

 

Here's an illustration that shows the principle:

 

 

Haha! Looks like something that could have been drawn on the wall of a public restroom! :D

[DAZnBLAST]

There is definitely something in this, wrong beam width or something, contacts not showing on F18 radar. I've flown in MP / SRS with F15s close formation before, they're shouting out contacts at 10, 12 , 2 o clock etc. I'm like what contacts? … in high, medium and intermittent modes, 40nm, 80nm, 160nm, azi high and low, 80 and 140 degrees sweep. They're like, you not see the contacts. The radar works, but no-where near as reliable as say F15, SU or M2K etc

[hornblower793]

There is definitely something in this, wrong beam width or something, contacts not showing on F18 radar. I've flown in MP / SRS with F15s close formation before, they're shouting out contacts at 10, 12 , 2 o clock etc. I'm like what contacts? … in high, medium and intermittent modes, 40nm, 80nm, 160nm, azi high and low, 80 and 140 degrees sweep. They're like, you not see the contacts. The radar works, but no-where near as reliable as say F15, SU or M2K etc

 

 

Not saying whether the Bug's radar is right or wrong, but 2 of those planes are not modelled to the same level and possibly have over effective systems

[*Rage*]

FC3 aircraft have AESA radars, to some extent.

[Beamscanner]

I think OP is confused. The 3.3 beam gets overlapped in its bar to bar raster scan. (About halfway) meaning a 2 bar scan would only cover 4.95 degrees in elevation

[SFJackBauer]

FC3 aircraft have AESA radars, to some extent.

 

The FC3 F-15C radar scans much faster than the Hornet, but its nowhere near AESA.