Modulation Acceptance Bandwidth; Rf Preselector Shape And Bandwidth; Receiver Frequency Adjustment - Motorola R-2200 Operator's Manual

5.7.0 MODULATION ACCEPTANCE BANDWIDTH
1.
Perform the I2 dB SINAD Sensitivity test with the
service monitor in the same set-up as shown in
figure 5.2.
2. Increase the RF output level 6 dB above the I2 dB
SINAD level, to double the voltage. For example,
0.35uV increased 6 dB=0.7uV.
3. Turn the "I KHz Lvl" control clockwise to increase
the deviation until the SINAD level returns to I2
dB. Read the amount of deviation on the display as
the modulation acceptance bandwidth of the re-
ceiver.
4. A typical modulation acceptance value for a re-
ceiver is 7 KHz. Refer to the specification for the
specific receiver under test. Any loss of modulation
acceptance bandwidth indicates improper align-
ment or a component failure in a receiver's IF cir-
cuit.
RF PRESELECTDR SHAPE AIID BANDWIDTH
D I D
\lwt:ISI\IAD/
Rf h/Out - - Ext ....... - Out Hod Out Ext Hod "
0 0 0 0 0
K.ECTIDN fl. TER
II..ECTIIN FRE0 SIJNM.
FIGURE 5.4- PROBE SETUP
5.8.0 RF PRESELECTOR SHAPE AND
BANDWIDTH
Use this test to insure proper preselector alignment for
multi-frequency receivers. Tune the preselector for
greater rejection of an interfering frequency from near-
by transmitters.
5-4
I. Connect the service monitor's "Antenna" to the
antenna connector of the receiver under test. Con-
nect the "Vert/SINAD/Dist" port to the RF probe.
Connect the probe to the first available low im-
pedance point following the preselector, as shown
in figure 5.4.
2. Disable the receiver's mixer injection.
3. Set scope to Ext Vert DC, "Function" to "Hi Gen",
modulation to "CW", and the scope sweep control
to "IOOuS/div".
4. Enter the approximate center frequency of the pre-
selector. Adjust the RF Level (and scope vertical
controls) to produce a trace on the CRT screen at
the lowest readable RF level to minimize the
possibility of overloading the circuits being tested.
5. Using the Frequency Stepping function, determine
at what frequency the peak DC voltage occurs on
the DVM or CRT.
6. The 3 dB (. 707 of peak) and 6 dB (.5 of peak) band-
width points can be checked by stepping either up
or down in frequency and observing the change in
DC level from the RF probe.
D
I
'Monl:M.:I:!OMHztl
E:J
t>.v • fnq •
0.0 ICHt Errar 0.00 ICHt
YwtiStc""/
Rf In/out Dlstii>IIM
0
Q
Ext HoriE Domod Out
0 0
Hod Out Ext Hod
In
0 0
LfiiT lJNDER TEST
FIGURE 5.5- FREQUENCY ADJUSTMENT SETUP
5.9.0 RECEIVER FREQUENCY ADJUSTMENT
I. Connect the service monitor to the receiver under
test, as shown in figure 5.5.
2. Set "Function" switch to "Sens Mon" (or "Anlzr
Sens Mon" on the R-2400). Program the monitor
for the local oscillator frequency.