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Service Manual
RF Cable Test
Figure 23. Duplex Test Screen
Tx Frequency
Off
Tx Power
dBm
-0.62
Tune Mode
Rf Gen Freq
Auto / Manual
834.990000
MHz
Tune Freq
Amplitude
834.990000
0.0
MHz
dBm
Atten Hold
Input Port
RF In / Ant
On / Off
IF Filter
Output Port
15 KHz
RF Out /
Dupl
Ext TX key
On / Off
In order to properly measure and adjust
the parameters of a telephone, it is im-
portant that you use RF cabling that has
minimal loss. Therefore, it is important
that you test the RF cable for proper loss.
This can easily be done by using the
DUPLEX TEST screen of your HP8920.
To test the cable, set up the DUPLEX
screen as shown above.
Action:
Take the cable under test and connect it
from the RF in/out port to the Duplex
Out port. At this point you will be get-
ting some type of power reading for cable
loss.
Good range: -.2 dBm through -.8 dBm
Bad cable:
More than -.8 dBm
DUPLEX TEST
AC Level
dB
SINAD
AF Anl In
AF Gen1 Freq
1.0000
Audio I n
Filter 1
AFGen1 To
50 Hz HPF
FM
Off
Filter 2
KHz
FM Coupling
15kHz LPF
AC / DC
DE Emphasis
Audio Out
750 us / Off
AC / DC
Detector
RMS
Motorola Confidential Proprietary
To test the RF cable for proper loss:
Off
•
Tune Freq should be set to TX fre-
quency: 834.990000 MHz.
Off
RF Gen Freq should be set to
•
same frequency (834.990000 MHz).
•
Tx Power should be set to read in
To Screen
dBm, not Watts.
RF GEN
RF ANL
AF ANL
SCOPE
SPEC ANL
ENCODER
DECODER
RADIO INT
More
If the reading you are getting shows gain
(positive number,) you may need to zero
the power meter. This may happen on
an HP8920 whose memory has just been
cleared.
To zero the meter, press the TX button
on the 8920 panel. Bring the cursor down
to the field under TX Pwr Zero where
it reads Zero. Tap the cursor on the Zero
field and it will highlight for a moment
as it zeroes the meter. Set up the screen
as shown above, and test your cable.
Test Procedures
RF Cable Test
37
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