870 

14 CFR Ch. I (1–1–19 Edition) 

§ 171.313 

(5) 

Antenna far field pattern in the 

vertical plane. 

The azimuth antenna 

free space radiation pattern below the 
horizon must have a slope of at least 

¥

8 dB/degree at the horizon and all 

sidelobes below the horizon must be at 
least 13 dB below the pattern peak. The 
antenna radiation pattern above the 
horizon must satisfy both the system 

coverage requirements and the spu-
rious radiation requirement. 

(6) 

Data antenna. 

The data antenna 

must have horizontal and vertical pat-
terns as required for its function. 

(g) 

Back azimuth coverage require-

ments. 

The back azimuth equipment 

where used must provide guidance in-
formation in at least the following vol-
ume of space (see Figure 11): 

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