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2.7.1.2
SPACE DIVERSITY OFFSET.
A potentiometer located near
Zl5
is
used
to
adjust the space diversity offset.
The
adjustment procedure
is exactly as above
e~cept
the space
diversity tie point is monitored with the oscilloscope.
2.7.1.3
AUTO MARK-HOLD THRESHOLD.
A potentiometer located
near Z22 is used to adjust the auto mark-hold threshold.
The
demodulator is connected and set up to receive an FSK signal
with 600 ohm step attenuator in series wi·th the input.
Monitor
TP3 with an oscilloscope, reduce the input level slowly from
0 dBm.
·The signal at TP3 will go from high to low when the
threshold is passed.
Adjust the potentiometer fo:r the desired
threshold (-55 dBm is nominal) •
2.7.2
Synthesizer Board
2.7.2.1
MARK MIXER BALANCE.
Apply an input signal to unit.
Monitor mark mixer outpat (TP5).
Adjust MX and MY pots until
the maximum excursions of the signal are superimposed, see
Figure
2-3.
Then adjust the MZ pot until
the signal
is
centered about zero volts.
This can be accomplished by using a
slower oscilloscope sweep so
that a sine wave eye pattern
appears on the scope and adjust for zero crossings at zero
volts.
Check also for symmetry of waveform, see Figure 2-4.
a.
Not Superimposed
b.
Superimposed
Figure 2-3.
Maximum Excursions
2-7
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