616 Chapter12
RF Section
A14 Frequency Control Assembly
positive 3.9107 GHz 1st IF offset between the desired harmonic of the
YTO frequency and the center frequency. This signal is 0.5 V/GHz of
tuned frequency and is available at the rear panel. The output can be
set for 0.50 V/GHz or 0.25 V/GHz.
1. On the spectrum analyzer, press
PRESET, and set the controls to the
following settings:
Start frequency ..............................................................0Hz
Stop frequency ....................................................... 26.5GHz
2. On the spectrum analyzer, press
AUX CTRL, REAR PANEL, and
V/GHz .25 .50 so that .50 is underlined.
3. Monitor the rear panel LO SWP | FAV OUTPUT with an
oscilloscope. The waveform should resemble Figure 12-5 on page
617.
4. Set the spectrum analyzer controls as follows:
Start frequency ........................................................... 8GHz
Stop frequency .......................................................... 10GHz
5. Monitor A14J15 pin 1 with an oscilloscope. The waveform should
resemble Figure 12-7 on page 618.
6. If the ramp is not correct, confirm the operation of the Main Coil
Tune DAC and Sweep Generator. Refer to “Unlocked YTO PLL” in
Chapter 11 .
7. Set the spectrum analyzer to the following settings:
Center frequency .......................................................... 5GHz
Span .................................................................................0Hz
8. Monitor A14J15 pin 3 with a DVM. For a center frequency of 5 GHz,
the voltage should measure −1.33 Vdc ±0.2 Vdc. Use the following
formula to calculate the voltage:
EQUATION {\rm V\sb {(J15\ pin\ 3)]] = {\rm {-0.25\ V \over
GHz}\ (freq\ in\ GHz)+offset} EQUATION
Offset voltage: −0.98 V in bands 0 and 5
−0.078 V in bands 1, 2, and 3
+0.98 V in band 4
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