17
3700 Osuna Road NE
Suite 711
Albuquerque, NM 87109
www.sandia.aero
To edit an adjustment, rotate the knob until the desired item is selected with a yellow box. Press the knob and
that element will be highlighted in blue. Rotate the knob to the desired value and resulting reading. Press the
knob to store the value and allow selection of another item.
3.7.3
Installation Adjustment
The SI-11X needs to be adjusted to the navigation receiver or GPS navigator that it’s interfaced to. Many
modern receivers have configuration pages that help in adjustment of the CDI. Garmin GNS4XX/5XX for
example have a configuration page to drive the needles to Full Left, Right, Up and Down that can assist in the
adjustment. A calibrated DMM is also useful in determining the voltages that are being applied by the
navigation system.
For a typical navigation receiver, the following steps should be performed with the receiver and a NAV Test
Set.
1.
Starting with the lateral VLOC needle, inject a strong localizer signal nav receiver.
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Adjust DDM to
zero and adjust the VLOC OFFSET so that VLOC READING is 0 +- 1.5 mV.
2.
The LOC FLAG READING should be greater than 125mV.
3.
Adjust DDM to .155 “Left” and adjust VLOC GAIN so that VLOC READING is 150mV +-1.5mV.
4.
Adjust DDM to .155 “Right” and Observe the VLOC READING is 150mV +-1.5mV.
5.
Remove the localizer signal and observe the VLOC FLAG READING is 0 + 1.5mV.
6.
Switch to the Glideslope receiver. Inject a strong glideslope signal. Adjust DDM to zero and adjust
GS OFFSET so that GS READING is 0 +- 1.5mV
7.
The GS FLAG READING should be greater than 125mV
8.
Adjust DDM to .175 “UP” and adjust GS GAIN so that GS READING is 150mV +-1.5mV.
9.
Adjust DDM to .175 “DOWN” and observe that GS READING is -150mV +-1.5mV
10.
Remove the glideslope signal and observe the GS FLAG READING is 0 + 1.5mV
The VLOC and GS needles should now be calibrated.
3.7.3.1
OBS Resolver Adjustment
Various navigation equipment has different methods for checking the operation of the OBS resolver.
Typically, the OBZ is set to 300, the RATIO is 1.0 and SWAP is 0. If the navigation equipment is reading
incorrectly, adjust the OBZ. If when incrementing the OBS and the navigation equipment readout is
decreasing, change the SWAP to 1. This will swap SIN/COS signals on STATOR D/F resulting in the proper
rotation direction.
Verify OBS operation by checking that the navigator is reading within 2 degrees. Do this at 30 degree
intervals.
3.7.3.2
VOR TO/FROM Check
After the needles and flags have been adjusted and the OBS Resolver is accurate, the system VOR operation
should be verified. Typically, the TO/FROM indications do not need adjustment.
3.7.3.3
Annunciator Checks
Operate the navigation equipment through its various modes and ensure that the connected ANNUNCIATOR
inputs are operating normally.
