Garmin AT
Rev --
© 2004 Garmin AT
GX Service Manual
7-39
Spurious Emission No Modulation
Step
General Instruction
Specific Instructions
Expected Results
1 Set
all
test
equipment as
specified in Test
Equipment Setup on
page 7-17.
2 Select
Spectrum
Analyzer.
On the HP8920, use the
CURSOR CONTROL knob to
select from the To Screen:
SPEC ANL. Push the CURSOR
CONTROL knob in to select.
The Spectrum Analyzer screen
is displayed.
3 Set
Spectrum
Analyzer.
Spectrum Analyzer Screen:
Using the
CURSOR CONTROL
knob and the DATA
keypad set:
Controls
Main RF In/Ant
Center Freq. 127.5 MHz
Ref Level
40 dBm**
Span 0.03
MHz
** If transmitter power is too
high, the REF Level will be too
close to noise floor of HP8920.
Adding an external 10 dB
attenuator will be necessary to
get lower noise floor.
4
Get to Marker Menu. Using the CURSOR CONTROL
knob, select Main. Push and
rotate the knob clockwise to
Marker.
5
On the test box, press the PTT
switch to TX.
6
Peak carrier and set
to reference.
In the Markers Menu, select
(Marker To) Select Peak.
Using the CURSOR CONTROL
knob, highlight Lvl dBm. Press
SHIFT (Blue key) REF SET.
The marker should be on top of
the carrier.
The marker value will go 0.00
dBm reference.
7
On the test box, press the PTT
switch to RX.
8
Put in filter to
suppress the carrier.
Install the 188 MHz high-pass
filter in series with the Comm
radio antenna coax directly on
the HP8920 RF IN/OUT port.
See Appendix B for HPF
Calibration Curve.
9
Set to first harmonic. Using the CURSOR CONTROL
knob, select Marker. Push and
rotate knob counterclockwise to
MAIN select. From the Main
Menu, select Center Freq. and
set to 255 MHz using the DATA
key pad.
10
Go to Marker Menu.
Using the CURSOR CONTROL
knob, select Main. Push and
rotate the knob to Marker.
Summary of Contents for APOLLO GX SERIES
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Page 27: ...2004 Garmin AT GX Service Manual 4 1 Chapter 4 Antenna Installation Guides...
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