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Diego
Topic Author
Posts: 135
Joined: Mon Apr 23, 2001 7:33 pm

Weather Radar

Tue Mar 15, 2005 4:23 am

hi folks a couple of questions for those avionics wizards outhere.
Reading a brochure about a weather radar I saw that there is a distinction, i guess referred to the band width of the radar between C and X? what does that refer to exactly and what kind of differences are there between the two bands? now still on that brochure there was a table that tied the size of the antenna spanning from 10 in to 30 in to the beam width that showed that the larger the antenna the narrower the beam width for example for an 18 inch antenna an X band radar will have a 5 degree beam width while the C band is not even available. Does anybody know the principal behind that and what size of antenna and band does the 737 use? thanks
 
danman
Posts: 39
Joined: Thu Jul 04, 2002 6:11 am

RE: Weather Radar

Tue Mar 15, 2005 7:40 am

I need to be sober for this, and I'm not but ..............
General rule
the higher the frequency the smaller the physical dimensions of the antenna for a given beamwidth.
C band is about 5 Ghz X band is 10 GHz more or less 9375 Mhz nominal.
Everything is a compromise, lower frequency, larger antenna, better range, lower definition, or higher frequency, smaller antenna, lower range, better definition.
I haven't come across a c band radar since the 707 - literally everything is X band as the best compromise
 
airplay
Posts: 3369
Joined: Sat Oct 25, 2003 1:58 am

RE: Weather Radar

Tue Mar 15, 2005 9:22 am

The major advantage of X band radar is the size of the components. As mentioned, there is a compromise in performance.

C band never made it big in aviation. As far as I know, it was only ever ordered by United Airlines. And that was because it used C band radar in trial tests of airborne weather radar.

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