Northern Airborne Technology NPX138 User Manual
Page 28
NPX138 Installation Approval Test Procedure
Rev. 1.10
Apr 19, 2004
Page 3 of 7
E NG-FORM: 634-0100.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
B.
Determine if the image frequency for the VHF Comm falls within the range of the
NPX138 unit. If so, select a set of frequencies that will cause the NPX138 to be
set as close as possible to the image frequency. Any one of the many possible
sets will suffice. Record these values in the spaces provided in the following
chart. Modulate the NPX138 transmitter on the following frequencies for at least
20 seconds. Listen for any noise or detected audio signals on the VHF comm.
Example - Bendix/King KY 196A:
The first IF frequency is 11.4 MHz. The L.O. is above the received frequency
(high side injection), therefore the image frequency is 22.8 MHz above the
selected frequency. Set the KY 196A to 120.000 MHz and the NPX138 to
142.8000 MHz.
FREQUENCIES RESULTS
VHF #1
NPX138 PASS
FAIL
135.975 138.0000
121.150 157.5000
131.250 157.5000
Image:
FREQUENCIES RESULTS
VHF #2
NPX138 PASS
FAIL
135.975 138.0000
121.150 157.5000
131.250 157.5000
Image:
NOTES: