Chapter 10 543
Synthesizer Section
Unlocked YTO PLL
Check the fractional N oscillator (steps 14-18)
13.Set the HP 8560E/EC to the following settings:
Center frequency .................................................. 300MHz
Span .............................................................................. 0Hz
14.Monitor the fractional N PLL output at A14J304 (FRAC N TEST)
with a synthesized spectrum analyzer such as an HP 8568A/B or HP
8566A/B. Refer to function block AI of A14 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 A14J304, about 30 dB less
than the fractional N signal, when unlocked.
16.If a problem exists only at particular center frequency 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 HP 8560E/EC 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 LODA (steps 19-22)
18.Set jumper A14J23 to the TEST position and set the HP 8560E/EC
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 LODA 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 A15U100J1.
Check sampler IF (steps 23-27)
22.Set the HP 8560E/EC to the following settings:
Center frequency .................................................. 300MHz
Span .............................................................................. 0Hz
23.Place jumper A14J23 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 HP 8568A/B or HP 8566A/B.
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