Motorola APX 7000 - Advanced Features; Geofence (ASTRO 25 Trunking System); Entering the Geofence Area

Troubleshooting Charts: RX RF Failure 5-33
5.15 RX RF Failure –Page 1
Inject a carrier wave with -47dBm
into antenna port. Remove shield,
SH3. Use a spectrum analyzer
and high-impedance RF probe to
measure the IF signal at the input
side of C601 going to the Abacus.
IF Frequency =
109.65 MHz?
Testing a
UHF1/VHF or
UHF1 / 7/800 or
UHF1/UHF2 or
UHF2/VHF or
UHF2/ 7/800
radio?
Poor RX
sensitivity or
no RX audio
No
No
Remove shield, SH12. IF level
at the mixer (output side of
series resistor, R511) about:
VHF: -44 dBm?
700: -48 dBm?
800: -45 dBm?
UHF1: -45 dBm?
UHF2: -46 dBm?
Yes
Yes
1
Yes
Yes
Remove shield, SH11.
Measure RF input level at the
antenna port (input side of
C1301).
RF level
about -49
dBm?
Remove shield, SH13.
Measure RF levels at the
input side of C1301 and the
input side of L1108,
compute RF switch, U1111
loss.
Yes
RF switch
loss < 1 dB?
Check digital logic
to the RF switch
and replace U1111
if needed.
No
Measure RF levels at the output side of L1108 and
the input side of C1122, compute RF switch, U1102
loss.
Note: The 15 dB attenuator in the RF switch will be
enabled.
RF switch
loss <17dB?
No
Yes
Testing a
VHF
channel?
Switch to a VHF channel.
Measure RF levels at input
side of C1122 and at the
input side of C301. Compute
RF switch, U1122 loss.
Testing a
700
channel?
No
Yes
RF switch
loss < 1
dB?
No
2
Inspect coaxial
antenna connector
and cable
assembly
Visual
inspection
OK?
Replace
bad part
Bad antenna
connector.
Replace cable
assembly.
No
No
Yes
No
Check digital logic
to the RF switch
and replace U1102
if needed.
Check digital
logic to the
RF switch
and replace
U1122
if needed.
Remove SH7.
Measure the LO
power going into the
mixer, U506, at the
output side of C599.
Remove shield, SH1.
Check the polarity
of T505 and check
to see that all pins
are grounded.
Visually inspect windings.
Remove SH7.
Measure the LO
power going into the
mixer, U506, at the
output side of C528.
Is the LO power
= -5 dBm?
Check FGU and
replace U506 if
needed.
Yes
Yes
No
Testing a
UHF1/VHF or
UHF1 / 7/800 or
UHF1/UHF2
UHF2/VHF or
UHF2 / 7/800
radio?
No
Yes
Replace T505
Check FGU and
replace U506 if
needed.
Is
polarity correct,
all pins gounded
and
windings look
ok?
No
Note: RF Test frequency used:
VHF: 154.275 MHz
UHF1: 424.975 MHz
UHF2: 485.075 MHz
700: 769.0625 MHz
800: 860.0625 MHz
Measured with a high impedance probe for relative comparisons and troubleshooting only.
Actual S21 gain or loss may differ if the test point is not 50 ohms.
Switch to a 700 channel.
Measure RF levels at input
side of C1122 and at the
input side of C402. Compute
RF switch, U1122 loss.
Yes
RF switch
loss < 2
dB?
No
3
Check digital
logic to the
RF switch
and replace
U1122
if needed.
Testing a
800
channel?
No
Switch to a 800 channel.
Measure RF levels at input
side of C1122 and at the
input side of C402. Compute
RF switch, U1122 loss.
Yes
RF switch
loss < 2
dB?
No
4
Check digital
logic to the
RF switch
and replace
U1122
if needed.
Testing a
UHF1
channel?
No
Switch to a UHF1 channel.
Measure RF levels at input
side of C1122 and at the
input side of C2035. Compute
RF switch, U1122 loss.
Yes
RF switch
loss < 2
dB?
No
15
Check digital
logic to the
RF switch
and replace
U1122
if needed.
Testing a
UHF2
channel?
No
Switch to a UHF2 channel.
Measure RF levels at input
side of C1122 and at the
input side of C1935. Compute
RF switch, U1122 loss.
Yes
RF switch
loss < 2
dB?
No
16
Check digital
logic to the
RF switch
and replace
U1122
if needed.
Yes Yes Yes Yes Yes