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Check the fractional N oscillator (steps 13-17)
13. Set the spectrum analyzer to the following settings:
Centerfrequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
14. Monitor the fractional N PLL output at A145304 (FRAC N TEST) with a synthesized
spectrum analyzer such as an HP
8568A/B
or HP
8566A/B.
Refer to function block AI of
Al4 frequency control schematic.
15. The signal at A14J304 (FRAC N TEST) should measure approximately -10
dBm
at
66.7 MHz. If the loop is unlocked, the sampler IF frequency can also be seen on A145304,
about 30 dB below the fractional N signal.
16. If a problem exists only at particular CENTER FREQ and SPAN settings, determine
the desired fractional N oscillator frequency by pressing (CAL),
NDRE
1
OF
2
,
F%lZg
DIAGlilOSE
, F&X 8
FREq
and setting the HP 85633 to SINGLE trigger mode.
17. If the fractional N oscillator frequency is not correct, refer to “Unlocked Fractional N
PLL” in this chapter.
Check sampler drive output of A7 SLODA (steps 18-21)
18. Set jumper A14J23 to the TEST position and set the spectrum analyzer to the following
settings:
Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 GHz
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
19. Disconnect cable W34 from A15UlOOJl.
20. Use a power meter to measure the A7 SLODA sampler-drive output at the end of W34.
The power should measure greater than -9
dBm.
21. Place jumper A14J23 in the NORMAL position and reconnect W34 to A15UlOOJl.
Check sampler IF (steps 22-28)
22. Set the spectrum analyzer to the following settings:
Center frequency
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.300
MHz
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
23. Place jumper A14J23 in the TEST position.
24. Disconnect W32 from
A15JlOl.
Monitor the sampler IF output (A15J101, SAMPLER IF)
with a synthesized spectrum analyzer such as an HP
8568A/B
or HP
8566A/B.
25. The sampler IF should measure between 46 MHz and 86 MHz at -15
dBm
to
+2
dBm.
If the signal frequency or amplitude is incorrect, refer to “Unlocked Offset PLL” in this
chapter.
26. Set jumper A14J23 in the NORMAL position. Reconnect W32 to
A15JlOl.
Check FM loop sense (steps 27-34)
27. Set jumper A14J23 in the TEST position.
28. Set the spectrum analyzer to the following settings:
Synthesizer Section 1
l-27