Garmin APOLLO GX SERIES Service Manual page 90

Garmin AT
Receiver Dynamic Range
Step General Instruction
1 Set all test
equipment as
specified in Test
Equipment Setup on
page 7-17.
2 RF Out to Dupl. Sig.
Gen. Mod Lvl. To
30%.
Amplitude to 1000
µV.
3 Move RF cable.
4 Adjust volume
control on Comm
radio for 12 W.
5 Open squelch.
6 Find 6 dB SINAD
reading.
7 Add 107dB.
8 Set HP8920 to 224
mV.
9
7-52
Specific Instructions
On the HP8920:
1. Set RF OUT/Dupl.
2. Set AFGen1 to AM 30%.
3. Set AMPLITUDE to 1000
µV.
4. Set Ext. Load R 4 ohms.
On the HP8920, move the
RFIN/OUT cable to DUPLEX out
connector.
On the Comm radio, adjust the
volume control until the AC Level
reads 12 watts.
On the Comm radio, pull the
Squelch knob out (disable
squelch).
On the HP8920, set the value
field in the SINAD meter reading
to average (AVG) at 10.
Set AMPLITUDE using the ↑ ↓
arrows until the SINAD meter
reads 6 dB SINAD.
On the HP8920:
1. Select the AMPLITUDE field.
Press the GHz/dBm key.
2. To calculate upper dynamic
range, add 107dB to
reference signal level.
On the HP8920:
1. Set the AMPLITUDE field to
upper dynamic range.
2. Select the SINAD field and
change to Distn.
Record as pass or fail.
GX Service Manual
Expected Results
≥12 watts output into 4 ohm
load (mounted in test fixture) at
a volume level from 0 to 12
watts.
Reference signal level ≤2 µV
(hard) for 6 dB S+N/N with 30%
modulation at 1000 Hz.
Converts µV to dBm.
Example: –107 dBm +107 = 0
dBm.
Dynamic range is 107 dB with
<5% distortion.
© 2004 Garmin AT
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