Poor Rx Sensitivity Or No Rx Audio (380–470 Mhz And 450–520 Mhz)—Part 1 Of 2 - Motorola ASTRO Digital XTL 5000 Detailed Service Manual

5-28
5.6.14 Poor RX Sensitivity or No RX Audio (380–470 MHz and 450–520 MHz)—Part 1
of 2
Sensitivity or no
Measure Transceiver
12dB Sinad by injecting
signal at antenna port
< - 117.5 dBm Std.
<-121dBm w/pre-amp
Check RF level at
Mixer LO injection port
Check RX front-end
Figure 5-18. Poor RX Sensitivity or No RX Audio (380–470 MHz and 450–520 MHz)—Part 1 of 2
May 25, 2005
Poor Rx
Rx audio
Yes
3kHz FM Deviation
1kHz Audio tone
Yes
12 dB Sinad
Sensitivity
Yes
No
at R5388
No
LO level
at + 24dBm?
Yes
tuning
No
Good?
Yes
1
Troubleshooting Charts: Flowcharts
Receiver
is working
properly
Check Receiver
VCO troubleshooting
flowchart
(LO injection section)
Retune Front-End
filters using tuner
and help screens
Check preselector circuit and
tuning control voltage.
Tuning control voltage should be:
~ 2V for 380 MHz and
~ 8V for 470 MHz (UHF Range 1)
~ 2.5V for 450 MHz and
~ 7.5V for 520 MHz (UHF Range 2)
6881096C74-B