136 Keysight EXG and MXG X-Series Signal Generators User’s Guide
Avionics VOR/ILS (Option 302)
Using ILS Localizer Softkeys
Example:
To correct if the right signal at 150 Hz is stronger at –0.2 DDM,
the aircraft would have to be pointed Left with a DDM of –0.2
The following steps of key presses demonstrate the correction for Left:
1.
Aux Fctn
>
Avionics
.
2.
ILS Localizer
>
DDM/SDM
>
Fly Left Right
to Left highlighted.
3.
DDM
>
–0.2
>
Enter
.
To set the ILS Localizer DDM value
This process sets a value for the Difference in Depth of Modulation (DDM).
1.
Press Aux Fctn > Avionics > ILS Localizer
2.
Press DDM/SDM
3.
Press DDM
(Default value is 0.0000.)
4.
Enter a value that is within the range of the current SDM value.
Typically the SDM default value provides sufficient range (–0.40 to 0.40)
for most applications.
If SDM is set to 99%, then the full range (-0.99 to 0.99) of DDM is
available. The following demonstrates the limits of DDM’s range:
(–SDM/100) to (SDM/100)
As SDM’s value increases or decrease, so does DDM’s range.
DDM is defined to be the “percentage modulation depth of the larger signal”
minus the “percentage modulation depth of the smaller signal”,
divided by 100.
DDM = [AM(90 Hz)% – AM(150 Hz)%] / 100
The primary mechanism which makes it possible for a pilot to obtain guidance
to a runway is the aircraft receiver's ability to detect the DDM between the 90
Hz and 150 Hz amplitude modulation.
To set the ILS Localizer DDM value in micro-amps (
μ
A)
This process sets a value for the difference in depth of modulation (DDM)
in
μ
A.
1.
Press Aux Fctn > Avionics > ILS Localizer.
2.
Press DDM/SDM.
3.
Press DDM uA
