Motorola Astro XTL 1500 - Poor RX Sensitivity or no RX Audio (380-470 Mhz and 450-520 Mhz)-Part 1 of 2

6815854H01-A June 15, 2005
Troubleshooting Charts: Flowcharts 5-25
5.6.14 Poor RX Sensitivity or No RX Audio (380–470 MHz and 450–520 MHz)—Part 1
of 2
Figure 5-16. Poor RX Sensitivity or No RX Audio (380–470 MHz and 450–520 MHz)—Part 1 of 2

Poor Rx
Sensitivity or no
Rx audio
Measure Transceiver
12dB Sinad by injecting
signal at antenna port
Yes
Yes
3kHz FM Deviation
1kHz Audio tone
12 dB Sinad
Sensitivity
< - 117.5 dBm Std.
<-121dBm w/pre-amp
Check RF level at
Mixer LO injection port
at R5388
Receiver
is working
properly
No
Yes
Good?
1
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)
No
Yes
LO level
at + 24dBm?
Check RX front-end
tuning
Check Receiver
VCO troubleshooting
flowchart
(LO injection section)
Retune Front-End
filters using tuner
and help screens
No
Yes