TROUBLESHOOTING: LO Output Test
3.3 RX Main VCO Test
Use this test on a unit with the following symptom: no RX.
Is there
a signal at the
SLEDGEHAMMER
VCO_IN port
?
Using a high impedance probe on
the spectrum analyzer, check the LO
output at the junction of C1 on the
SLEDGEHAMMER VCO_IN port.
Probe for the LO signal by placing
the probe on the VCO module pin 1.
The level will be low. Adjust the
spectrum analyzer accordingly.
Check for opens,shorts, or
missing components
on the SFout line.
Check band select lines. For 800
band, voltage at C332 is low and
voltage at C331 is high. For 900
band, voltage at C332 is high
and voltage at C331 is low.
Check for opens, shorts, or missing
components on the RF_OUT out
path. Check for a bad connection
from the VCO module to the radio
board or a bad VCO module.
The FGU is working properly.
Further investigation in the
FGU requires noise
performance or locktime
testing, such as
H&N or SBN.
Check for opens, shorts, or missing
components on R323, R324, R326,
C322, C323, C324, C325, C326, C327,
C328, C347. Check for a bad connection
from the VCO module to the radio board.
Yes
No
Is
Level >2.5 V
?
Is
the LO signal at
VCO output
?
Is
SFout voltage
(2.55 Vdc) at pin 5
Is
the signal level at
least 70mV Rms
?
Is
the signal at
1702.250 MHz
(800 band) or
1870.0375 MHz
(900 band)
?
Check for opens, shorts,
or missing components
On C331, C332.
If OK, see Digital Analysis Tests.
Yes
No
Yes
No
Note: Run the RX BER
851.0125 Test before
beginning this test. (Run
the RX BER 935.01875
Test before beginning to
test the 900 MHz band.)
LO Frequency Range: 2x RX Freq.
851.0125 MHz = 1702.025 MHz (800 band)
935.01875 = 1870.0375 MHz (900 band).
No
NoNo
No
Yes
Yes
Yes
Continued
on next
page
If no opens/shorts or
missing components are
found, on SFout line,
Replace the
ROADRUNNER.
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