Avionic standards
R&S
®
SMA100B
131User Manual 1178.3834.02 ─ 09
Localizer
The localizer transmitter is located near the end of the runway (nearest to the start of
the aircraft approach). Typically, horizontally aligned antennas transmit two intersecting
main beams beside one another at carrier frequencies between 108 MHz and 112 MHz
(see Table 6-2). As seen from the approaching aircraft coming in for a landing, the left
beam is usually modulated at 90 Hz and the right beam at 150 Hz [1MA193].
The information on position is provided after demodulation of the beam signals by eval-
uating the difference in depth of modulation (DDM). The following scenarios are possi-
ble:
●
Predominance of the 90 Hz beam: the aircraft is too far to the left and must turn to
the right
●
Predominance of the 150 Hz beam: the aircraft is too far to the right and must turn
to the left
●
The signal strength from both beams is equal: the aircraft is in the center, on the
right course.
ILS ICAO Frequencies
The individual values in the table below are:
●
Chan. = ICAO channel number
●
LOC Freq. = ILS localizer frequency (MHz)
●
GS Freq. = ILS glide slope frequency (MHz)
Table 6-2: ILS glide slope and localizer ICAO standard frequencies (MHz) and channels
Chan. LOC Freq. GS Freq.
Chan. LOC Freq. GS Freq.
Chan. LOC Freq. GS Freq.
18X
18Y
108.10
108.15
334.70
334.55
32X
32Y
109.50
109.55
332.60
332.45
46X
46Y
110.90
110.95
330.80
330.65
20X
20Y
108.30
108.35
334.10
333.95
34X
34Y
109.70
109.75
333.20
333.05
48X
48Y
111.10
111.15
331.70
331.55
22X
22Y
108.50
108.55
329.90
329.75
36X
36Y
109.90
109.95
333.80
333.65
50X
50Y
111.30
111.35
332.30
332.15
24X
24Y
108.70
108.75
330.50
330.35
38X
38Y
110.10
110.15
334.40
334.25
52X
52Y
111.50
111.55
332.90
332.75
26X
26Y
108.90
108.95
329.30
329.15
40X
40Y
110.30
110.35
335.00
334.85
54X
54Y
111.70
111.75
333.50
333.35
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