Motorola R-2400 Operator's Manual page 43

Set
the "Function" switch
to "Pwr
Mon/AnLzr
On"
and attenuator
to -30
dB. Verify that
the
display's center frequency reads
the
same as the
transmit
frequency
in
step
A-7
above.
Key the transmitter and adjust the reject notch
adjustments
on the duplexer
receiver leg cavities
for
minimum
signal
on the display. Change
the
attenuator,
as
necessary,
to
keep
the signal on the
display.
Loosen the cavity reject adjustment
nut
and slide
it
within its slot while
watching
the
display.
Tighten the adjustment
nut. Be careful
not
to
mistune
the rejection adjustment. Fine tune
the
rejection adjustment
by
turning the
bandpass
knob a maximum
of
+
/
-15
degrees.
This
com-
pletes
the duplexer receiver leg
reject notch
ad-
justment.
RE.fCT
FIGURE
5.13
*DUPLEXER ADJUSTMENT
SETUP;
REJECT NOTCH ON TRANSMIT LEG
5.16.0 CAVITY & DUPLEXER TUNING
BANDPASS
WITH
RETECT NOTCH
C.
Adjustment
of
Reject
Notch on Transmit
Leg
l.
Connect the
service
monitor's "RF
InlOut"
to
the
in-service duplexer
as
shown
in
figure
5.
13.
Dis-
connect the cable at the
duplexer transmitter
port
that comes
from
the
transmitter. Move the
serv-
ice
monitor's
"RF InlOut"
cable
from
the
duplexer receiver
port to the
duplexer transmis-
sion
port.
Reconnect the
cable
coming from
the
receiver
to
the
duplexer
receiver
port.
Disable the
receiver
PL.
2.
Set
"Function" switch
to "Gell", "FM",
and enter
the receiver frequency.
Set
the
attenuator
to
-30 dB and the
"RF
Vernier"
to
mid-ratrge,
to
allow
adequate signal
to get through the duplexer and quiet the
re-
ceiver. Reduce
the signal generator
output,
&S
necess
dry,
to
keep
the
receiver
limiter
meter
below saturation.
Adjust the reject notch
adjustments
on
the
duplexer transmit leg cavities
for minimum
signal
level on the
receiver
limiter
meter.
Change the
signal
generator output,
as
necessary,
to
keep the
received signal
up out
of
the noise and
below
saturation.
Loosen the
cavity reject adjustment
nut
and slide
it
within
its
slot while
watching
the
meter.
Tighten the adjustment
nut.
Be careful
not
to
mistune
the rejection adjustment. Fine-tune the
reject notch adjustment
by turning the bandpass
knob
a
maximum
of
+
/-15
degrees.
Remove
the test
equipment
and
connect
the
duplexer back
to
the repeater. Check
the
du-
plexer
for
insertion
loss
according to
its specifica-
tions.
FIGURE s.I4-DESENSITIZATION TEST
SETUP
5.I.7.0
DESENSITIZATION TEST
IN
SERVICE
DUPTEXER
Perform this test after retuning
a
duplexer
or
after
detecting inadequate
isolation
between
transmitter
and
receiver.
The following conditions may make
a
duplexer
appear mistuned:
High VSWR
antenna
IM
(intermodulation)
between repeater's
transmit-
ter
and an external signal
Faulty
cables
or
connectors
Improper
cable
length
or configuration
3. 2.
3.
4.
4.
5.
6.
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