Chapter 11 609
RF Section
A10 Tracking Generator (Option 002)
messages.) If the start frequency is changed to be greater than 300 kHz
and the output is still unleveled, ERR 900 TG UNLVL will be displayed
(see above).
The ALC MON line is monitored only at the end of a sweep. For this
reason, it is possible that the output could be unleveled during a portion
of a sweep, and, if the output returns to a leveled condition by the end of
the sweep, ERR 900 TG UNLVL will not be displayed.
If ERR 900 TG UNLVL is displayed, proceed as follows:
1. Check at which frequencies the output is unleveled. Set the
spectrum analyzer to zero span and step the center frequency in 50
MHz increments. Note at which frequencies the output is unleveled.
2. Check at which power levels the output is unleveled. Connect the RF
OUT 50 Ω to the INPUT 50 Ω connector. With the spectrum analyzer
in zero span, set the center frequency to 300 MHz or one of the
frequencies noted in step 1. Press
AUXCTRL, TRACKING
GENRATOR, SRC PWR ON, MORE 1 OF 3, TRACKING PEAK. Wait for
the "PEAKING" message to disappear. Step the TRK GEN RF
POWER setting in 1 dB increments and note at which power levels
the output is unleveled. It is acceptable for the output to be
unleveled only at power levels greater than the specified maximum
leveled output power level.
3. Check maximum power available from the TG. Connect the RF OUT
50 Ω to the INPUT 50 Ω connector. Press
PRESET, AMPLITUDE, 2, 0, +
dBm, LOG dB/DIV, 5, dB, AUX CTRL, TRACKING GENRATOR, SRC PWR
ON, MORE 1 OF 3, ALC EXT. No connection should be made to the ALC
EXT INPUT connector on the rear panel. The available power
should always be greater than +1 dBm. If the output is unleveled
only at specific frequencies, a power hole will usually be visible at
those frequencies.
4. Perform the "1ST LO OUTPUT Amplitude" performance test. If the
test fails, note the center frequency setting at which the power level
was out-of-tolerance. Repeat the test with the power sensor
connected to A7J3 (a right-angle SMA adapter will be necessary)
and note the center frequency of any out-of-tolerance power levels.
The power level should be +16.5 dBm ±2 dB.
If the power level is correct at W43 but out-of-tolerance at the 1ST
LO OUTPUT (front panel), and the center frequency setting of the
out-of-tolerance power levels is close to the frequencies at which the
output is unleveled, suspect either A10 or W46.
If the power level at W43 is also out-of-tolerance, suspect either the
A7 LODA or the A11 YTO. Refer to Chapter 10, "Synthesizer
Section."
5. If the output is unleveled only at certain power level settings or
certain frequencies, monitor A17J16 pin 1 with a DVM. Connect the
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