Instrument Function > Modulation > ILS-GS Modulation > ILS-GS Modulation Settings
ILS-GS Modulation Settings

The "ILS-GS Modulation" dialog is opened in the "Mod" function block or using the MENU key under "Mod".

In the upper section, the modulation source is selected and the modulation switched on. The configuration of the selected external and/or internal modulation source is performed in the lower section of the dialog.

State - ILS-GS Modulation

Activates ILS-GS modulation.

Activation of ILS-GS modulation deactivates AM, VOR, ILS-LOC, Marker Beacon and ADF modulation.

Source selection and the associated parameters are disabled in the "LF Generator / Output" dialog:

Remote command: 
 
DDM Polarity - ILS-GS Modulation

Defines the polarity for DDM calculation (see DDM Depth).

Remote command: 
 
Sum of Depth - ILS-GS Modulation

Enters the arithmetic sum of the modulation depths of the upper lobe (90Hz) and lower lobe (150Hz) ILS-GS signal contents. The RMS modulation depth of the sum signal depends on the phase setting of both modulation tones. The sum of Sum of Depth and COM/ID depth must be smaller than 100 PCT.

Remote command: 
 
Fly - ILS-GS Modulation

Selects the simulation mode for the ILS-GS modulation signal. A change of the setting automatically changes the sign of the DDM value.

This setting simulates the direction in which the pilot has to correct the course.

"Up"

The 150-Hz modulation signal is predominant, the DDM value is negative(the airplane is too low, it must climb).

"Down"

The 90-Hz modulation signal is predominant, the DDM value is positive (the airplane is too high, it must descend).

Remote command: 
 
DDM Current - ILS-GS Modulation

Enters the current of the ILS indicating instrument corresponding to the DDM value. the instrument current is calculated according to:

DDM uA = DDM × 857,125 uA

A variation of the instrument current automatically leads to a variation of the DDM value and the DDM value in dB.

Remote command: 
 
DDM Depth - ILS-GS Modulation

Enters the difference in depth of modulation between the upper lobe (90Hz) and the lower lobe (150Hz) tone of the ILS-GS modulation signal.

The DDM value is calculated to formula:
  • Polarity 90 Hz - 150 Hz (default setting):
    DDM = [ AM(90 Hz) - AM (150 Hz) ] / 100%
  • Polarity 150 Hz - 90 Hz:
    DDM = [ AM(150 Hz) - AM (90 Hz) ] / 100%

A variation of the DDM value automatically leads to a variation of the value of the instrument current and the DDM value in dB.

Remote command: 
 
DDM Logarithmic - ILS-GS Modulation

Enters the DDM value in dB. The dB value is calculated according to:

DDM dB = 20 × LOG [(SDM+DDM×100%) / (SDM-DDM×100%)]

A variation of the value automatically leads to a variation of the DDM value and the instrument current.

Remote command: 
 
DDM Percent - ILS-GS Modulation

Enters the difference in depth of modulation between the upper lobe (90Hz) and the lower lobe (150Hz) tone of the ILS-GS modulation signal.

The DDM value in percent is calculated to formula:
  • Polarity 90 Hz - 150 Hz (default setting):
    DDM = [ AM(90 Hz) - AM (150 Hz) ]
  • Polarity 150 Hz - 90 Hz:
    DDM = [ AM(150 Hz) - AM (90 Hz) ]

A variation of the DDM value automatically leads to a variation of the value of the instrument current and the DDM value in dB.

Remote command: 
 
DDM - SDM Coupling - ILS-GS Modulation

Selects if the DDM value is fixed or is changed with a change of sum of modulation depths (SDM, see below).

"Fixed"

The absolute DDM values stays constant when the SDM is changed.

"SDM"

The absolute DDM values changes when the SDM is changed. The DDM value expressed in dB stays constant.

Remote command: 
 
Mode - ILS-GS Modulation

Selects the operating mode for the ILS-GS modulation signal.

"Norm"

ILS-GS modulation is active.

"90 Hz"

Amplitude modulation of the output signal with the upper lobe signal component (90Hz signal content) of the ILS-GS signal.

The modulation depth of the 90-Hz signal results from the settings of parameters "Sum of depth (SDM)" and "DDM" according to:
  • "Direction Down"
    AM(90 Hz) = 0.5 × (SDM + DDM × 100%)
  • "Direction Up"
    AM(90 Hz) = 0.5 × (SDM - DDM × 100%)

"150 Hz"

Amplitude modulation of the output signal with the lower lobe signal component (150-Hzsignal content) of the ILS-GS signal.

The modulation depth of the 150-Hz signal results from the settings of parameters "Sum of depth (SDM)" and "DDM" according to:
  • "Direction Down"
    AM (150 Hz) = 0,5 × (SDM + DDM × 100%)
  • "Direction Up"
    AM (150 Hz) = 0,5 × (SDM - DDM × 100%)
Remote command: 
 
Up Frequency - ILS-GS Modulation

Enters the modulation frequency of the upper antenna lobe.

Remote command: 
 
Down Frequency - ILS-GS Modulation

Enters the modulation frequency of the lower antenna lobe .

Remote command: 
 
Up/Down Phase - ILS-GS Modulation

Enters the phase between the modulation signals of the upper and lower antenna lobe. The zero crossing of the lower lobe (150Hz) signal serves as a reference. The angle refers to the period of the signal of the lower antenna lobe.

Remote command: 
 
Set to Default - ILS-GS Modulation

Activates the ILS-GS default setting.

Parameter

Value

State

Off

Sum of Depth

80 Percent

Fly

Up

DDM

0

Mode

Norm

Up Frequency

90 Hz

Down Frequency

150 Hz

Up/Down Phase

0 deg

COM/ID State

Off

COM/ID Frequency

1020 kHz

COM/ID Depth

10 percent

Remote command: 
 
DDM Knob Step - ILS-GS Modulation

Selects the variation of the DDM values via the rotary knob.

"Decimal"

Decimal variation according to the current cursor position.

"Defined"

Variation in predefined steps according to the standardized DDM values:
  • -0.4000
  • -0.1750 (Glide Sector)
  • -0.0910, 0,0450
  • 0.0000 (Glide Path)
  • +0.0450, +0,0910
  • +0.1750 (Glide Sector)
  • +0.4000
Remote command: 

n.a.

 
Carrier Frequency Step - ILS-GS Modulation

Selects the variation of the carrier frequency via the rotary knob.

"Decimal"

Decimal variation according to the current cursor position.

"ICAO"

Activates variation in predefined steps according to the standardized ILS-GS transmitting frequencies (see table, values in MHz). The start value can be selected in the field "ICAO Channel" below.

The selection of the ICAO channel is effective on both ILS modulations. A change to modulation ILS-LOC automatically causes the RF frequency to be adapted to the localizer value which is coupled to the glide slope setting (see table).

The individual values in the table are:
  • Ch. No. = ICAO channel number
  • LOC Freq. = ILS Localizer transmitting frequency (MHz)
  • GS Freq. = ILS GS frequency (MHz)
Standardized ILS-GS and ILS-LOC transmitting frequencies (MHz) and the associated ICAO channels

Ch. No.

LOC Freq.

GS Freq.

 

Ch. No.

LOC Freq.

GS Freq.

 

Ch. No.

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

22X

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

28X

28Y

109.10

109.15

331.40

331.25

 

42X

42Y

110.50

110.55

329.60

329.45

 

56X

56Y

111.90

111.95

331.10

330.95

30X

30Y

109.30

109.35

332.00

331.85

 

44X

44Y

110.70

110.75

330.20

330.05

    
Remote command: 
 
ICAO Channel - ILS-GS Modulation

Selects the ICAO channel, i.e., the ILS-GS transmitting frequency. The RF-frequency is set to the value selected here. A variation of the carrier frequency by the rotary knob is performed in predefined steps according to the standardized ILS-GS transmitting frequencies (see table). The ICAO channel settings for ILS-GS and ILS-LOC are coupled.

Remote command: 
 
Change to ILS-LOC - ILS-GS Modulation

Changes to ILS-LOC modulation and opens the menu. The current state of the ILS GS modulation (On or Off) is also set for ILS-LOC. The RF frequency setting automatically changes to the transmitting frequency associated with the set ICAO channel for ILS-LOC if the state is on. .

Remote command: 

n.a.

 
EXT AM - ILS-GS Modulation

Switching on/off an external modulation. The external signal is input via the AM EXT connector.

"Off"

Selects the internal modulation source for ILS-GS modulation.

"EXT (MOD AM)"

Selects the external source. The external signal is added to the internal signal. Switching off the internal source is not possible. The external signal is input via the AM EXT connector. The sensitivity is 10 mV per percent modulation depth.

Note: There can be an overmodulation as a function of the level of the external signal without a corresponding caution message being generated.In order to avoid an overmodulation, the peak value of the external signal is to be delimited corresponding to the sum of the modulation depths of the remaining ILS signal components.

Remote command: 
 

 


Imprint | Statement of Privacy | Terms & Conditions© 2016 ROHDE & SCHWARZ