Tx Deviation Limit - Motorola ASTRO XTL 5000 Basic Service Manual

6-14
6.4.9

Tx Deviation Limit

NOTE: This alignment is required after replacing (or servicing) components on the transceiver board.
The Tx Deviation Limit alignment procedure limits the modulation of a baseband signal. It is used for
primary modulation limiting. This procedure needs to be performed at multiple frequencies to allow
for proper alignment across the entire RF band. The RF band is divided into frequency zones with a
calibration point (value) in each zone.
This test can be done with either the R-2670 Communication Analyzer or the Agilent 8901
Modulation Analyzer. The method of choice is the R-2670 Analyzer.
• Initial set up using the R-2670 Communication Analyzer:
- Connect a BNC cable between the "DEMOD OUT" port and the "VERT/SINAD DIST/DMM
COUNTER IN" port on the R-2670.
- Press the SPF key on the R-2670 to display the "SPECIAL FUNCTIONS MENU." Move the
cursor to "High Pass," and select 5 Hz on the soft key menu. Select 20 kHz for the "Low
Pass" setting.
- In the "RF Control" section of the R-2670, enter the frequency displayed on the tuner
screen. Move the cursor to the "B/W" setting and select "WIDE
menu.
- Place the R-2670 cursor in the "Display" zone. Select "AC VOLTS" on the soft key menu.
- Move the cursor to the "Range" setting and select "AUTO."
• Initial set up using the 8901 Modulation Analyzer:
- Press the FM MEASUREMENT button. (The "Error 03-input level too low" indication is
normal until an input signal is applied.)
- Simultaneously press the Peak - and Peak + buttons. Both LEDs on the buttons should
light.
- Press the 15 kHz LP filter key.
1. Select TX Deviation Limit from the Tuner Main Menu. The screen will indicate the transmit
frequencies to be used. See
June 11, 2003
Radio Alignment Procedures: Transmitter Alignments
Figure 6-12 on page 6-15.
±
100 kHz" on the soft key
6881096C73-O