556 Chapter11
Synthesizer Section
Unlocked YTO PLL
16.If a problem exists only at particular CENTER FREQ and SPAN
settings, determine the desired fractional N oscillator frequency by
pressing
CAL, MORE 1 OF 2, FREQ DIAGNOSE, FRAC N FREQ and
setting the spectrum analyzer 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 LOMA (steps
18-21)
18.Set A14J23 jumper to the TEST position and set the spectrum
analyzer to the following settings:
Center frequency .................................................... 2.9GHz
Span ..............................................................................0Hz
19.Disconnect cable W34 from A15U100J1.
20.Use a power meter to measure the A7 LOMA sampler-drive output
at the end of W34. The power should measure greater than −9 dBm.
21.Place A14J23 jumper in the NORMAL position and reconnect W34
to A15U100J1.
Check sampler
IF (steps 22-26)
22.Set the spectrum analyzer to the following settings:
Center frequency .................................................. 300MHz
Span ..............................................................................0Hz
23.Place A14J23 jumper in the TEST position.
24.Disconnect W32 from A15J101. Monitor the sampler IF output
(A15J101, SAMPLER IF) with a synthesized spectrum analyzer
such as an 8568A/B or 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 A14J23 jumper in the NORMAL position. Reconnect W32 to
A15J101.
Check FM loop
sense (steps
27-34)
27.Set A14J23 jumper in the TEST position.
28.Set the spectrum analyzer to the following settings:
Center frequency .................................................. 300MHz
Span ..............................................................................0Hz
29.Connect an RF signal-generator output to A14J501. Set the signal
generator to the following settings:
Frequency .................................................................. 56MHz
Amplitude .................................................................... 0dBm
30.Monitor A14J17 pin 1 with a DVM or oscilloscope. Connect ground to
A14J17 pin 6.
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