612 Chapter11
RF Section
A10 Tracking Generator (Option 002)
ignoring the desired output signal. If any spurious responses are
greater than −20 dBc, the vernier accuracy measurement may fail.
Refer to "Harmonic/Spurious Outputs Too High" in this chapter.
3. Check for excessive LO feedthrough. Use the "LO Feedthrough"
performance test in the HP 8560 E-Series Spectrum Analyzer
Calibration Guide, but check over a center frequency range of 300
kHz to 100 MHz. The LO feedthrough will be 3.9107 GHz greater
than the center frequency setting.
Harmonic/Spurious Outputs Too High
Harmonic and spurious outputs may be generated by A10 itself or may
be present on the either the 600 MHz drive or 1st LO drive signal.
There is a direct relationship between spurious signals on the 1st LO
and spurious signals on the TG output. There is a five-to-one
relationship between spurious signals on the 600 MHz drive and the
spurious signals on the TG output. For example, if the 600 MHz signal
moves 1 MHz, the TG output signal will move 5 MHz. This is due to the
multiplication in the pentupler.
1. If the "Harmonic Spurious Responses" performance test failed,
connect another spectrum analyzer, such as an HP 8566A/B, to the
HP 8560E/EC 1ST LO OUTPUT connector. Set the HP 8560E/EC to
each frequency as indicated in the performance test, with the span
set to 0 Hz. At each frequency setting, press
SGL
SWP, CAL, MORE 1 OF 2, FREQ DIAGNOSE, LO FREQ. The frequency
displayed will be the fundamental frequency of the 1ST LO
OUTPUT. Use the HP 8566A/B to measure the level of the second
and third harmonics of the 1st LO signal.
NOTE The 1st LO typically has a higher harmonic content than the tracking
generator output. For the purposes of this check, it is the variation in
harmonic content versus frequency which is important.
If the variation of the harmonic level of the 1st LO versus frequency
tracks the harmonic level variation of the tracking generator output,
repeat this step while measuring the 1st LO signal at the end of W43
nearest A10. If there is little variation in the 1st LO harmonic level
between the 1ST LO OUTPUT connector and W43, and the relative
variation in harmonic level tracks with the TG output harmonic
level, suspect either the A7 LODA or A11 YTO.
If the harmonic level variation of the 1st LO versus frequency does
not track the harmonic level variation of the TG output, suspect A10.
2. If sidebands are present at the same frequency offset at every output
frequency, check the spectral purity of the 1st LO and the 600 MHz
drive signals using another spectrum analyzer. When checking the
1st LO, the HP 8560E/EC must be set to zero span. Press
CAL,
MORE 1 OF 2, FREQ DIAGNOSE, LO FREQ to determine the 1st LO
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