HP 11710A Operating And Service Manual page 12

Page 8
Model 11710A
PERFORMANCE TESTS
Performance Tests on Down-Converted Signal (Cont'd)
48.
g-
h. Repeat steps d and e.
i.
j.
k.
60 dBc.
1.
— 80 dBm
ADJUSTMENTS
49. Local Oscillator Frequency Adjustment
igure 11. RE ERENCE:
DESCRIPTION:
PROCEDURE:
(Cont ' d)
An oscilloscope, triggered by an external reference, is used to set the local oscillator
(LO) frequency. If the generator to be used with the Down Converter has a counter
readout, the LO is adjusted using the generator ' s reference. Otherwise, the frequency
is adjusted to 5 MHz using a suitable frequency standard.
Set generator ' s output level to — 87 dBm and frequency to 5.1 MHz. Set spectrum
analyzer ' s frequency span to 5.1 MHz, input attenuation to 0 dB, and linear sensi ­
tivity to 2 n V/division.
Adjust spectrum analyzers vertical reference level to bring signal to top graticule
line. Tune generator frequency through 5.00 to 5.5 MHz range while observing
second and third harmonics on analyzer display. If desired, adjust analyzer ' s fre ­
quency span, center frequency, and resolution bandwidth. Harmonics should be
greater than 35 dB below fundamental.
Set spectrum analyzer ' s resolution bandwidth to 10 kHz, frequency tune to
10 MHz, and frequency span to 2 MHz per division. Tune signal generator to
5.5 MHz. All signals except 500 kHz fundamental and its harmonics should be
greater than 60 dB below the fundamental.
Disconnect R input to Down Converter. Set spectrum analyzer ' s resolution band ­
width to 3 kHz, frequency tune to 5 MHz, frequency span to 0.2 MHz per division,
and input attenuation to 0 dB. ine tune analyzer to locate 5 MHz signal. Signal
level should be less than — 80 dBm. If it is not, adjust A1R5 (5 MHz Null) for
lowest signal level.
Set spectrum analyzer ' s input attenuation to 40 dB and vertical reference level to
0 dBm (log). Set generator ' s output level to 0 dBm.
NOTE
If the signal level cannot be adjusted properly in step I, monitor
signal at A1TP2 and adjust for lowest signal level. Repeat step I
and verify output is within specification.
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