Garmin APOLLO GX SERIES Service Manual - page 75
Garmin AT
Rev --
© 2004 Garmin AT
GX Service Manual
7-37
Step General Instruction
Specific Instructions
Expected Results
8
Change AF Freq. to
350 Hz.
Using the CURSOR CONTROL
knob and the DATA keypad, set
AFGen1 Freq. to 0.350 kHz.
9
Key the transmitter.
On the test box, press the PTT
switch to TX.
10
Read the difference. Read and record the AF Depth
difference.
The variation will be <4 dB at
85% modulation from 350 Hz to
2.5 kHz.
11
On the test box, press the PTT
switch to RX.
12
Repeat steps 9 to 12 for every 200
Hz until 2500 Hz is obtained.
The variation will be ≤4 dB at
85% modulation from 350 Hz to
2.5 kHz.
Modulation Audio Frequency Distortion
Step
General Instruction
Specific Instructions
Expected Results
1 Set
all
test
equipment as
specified in Test
Equipment Setup on
page 7-17.
On HP8920, set AFGen1 to 20
mV.
2
Key the transmitter.
On the test box, press the PTT
switch to TX.
3
Adjust audio level
input to obtain 85%
modulation ± 1%.
Using the CURSOR CONTROL
knob or the ↑ arrows, adjust the
AFGen1 Lvl until 85%
modulation is viewed on the
HP8920 (AM Depth). NOTE:
Always approach the desired
modulation from lowest audio
input level and stop when
desired modulation is obtained.
It may be necessary to set INCR
+divide10, or INCR SET or INCR
X10 to obtain a reading of
I=0.00100 for fine adjustment.
NOTE: Due to the 35-second
time out, the PTT switch may be
toggled from RX to TX to
maintain TX power during
adjustment.
Confirm the AF Freq. meter
reads 1 kHz at 85% modulation
± 1%.
4
Read distortion.
On the HP8920 set the AF Freq.
field to Distn. Record distortion.
The distortion will be <10% at
85% modulation.