Garmin APOLLO GX SERIES, Service Manual

Page: 88 / 166

Garmin AT Rev --
7-50 GX Service Manual © 2004 Garmin AT
Speaker Distortion
Step General Instruction Specific Instructions Expected Results
1 Set all test
equipment as
specified in Test
Equipment Setup on
page 7-17.
2 On the HP8920:
1. Ext. Load R to 4 ohms.
2. AFGen1 to AM 85%.
3. AMPLITUDE to 1,000 µV.
3 Move test cable. On the test box, connect the
HP8920 audio in cable to SPKR
OUT.
4 Adjust volume
control on Comm
radio for 12 W.
On the Comm radio, adjust the
volume control until the AC Level
reads 12 watts.
5 On the HP8920, select Distn
from the one of many field. Speaker at 1000 Hz distortion
should be < 5%.
6 NOTE: Option 019
required for the
HP8920A. If Option 019 (the notch filter
option) is not installed, an
external variable notch filter will
be required to complete the
following tests.
7 On the HP8920, push the SHIFT
(blue key) CONFIG keys under
SCREEN CONTROL. Select
Notch Coupl. Set to AFGen1.
Push the PREV key under
SCREEN CONTROL to return to
RX TEST. Lock notch filter to AF Gen1
Freq.
8 Notch filter freq. to
350. On the HP8920, AFGen1 Freq. 350 Hz.
9 Record distortion. Will be <12% distortion at 350
Hz.
10 Repeat steps 7 to 9 for every
200 Hz until 2500 Hz. Audio frequency distortion will
be <12% at AM Depth of
modulation of 85% at 350 Hz to
600 Hz and <5% from 600 Hz
to 2500 Hz.