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Table 8-1. Numbered Error Messages (8 of 17)

4 If you do not know the modulation bandwidth for your VCO source, you can determine it

(cont'd) by locating the 3 dB roll-off frequency of the VCO tune port. The following steps describe

a procedure for determining the modulation bandwidth.

a. Connect a tracking generator output (such as the HP 3585A) to the tuning input port

on your VCO.

b. Set the tracking generator output to sweep the audio spectrum.

c. Connect the RF output from your VCO to a modulation analyzer (such as an

8901

A).

Set the modulation analyzer to measure FM.

e. Connect an audio spectrum analyzer to the MODULATION OUTPUT on the

8901

1. Increase the frequency spectrum of the tracking generator, if necessary, until the

3 dB roll-off frequency can be seen on the audio analyzer's display. The 3 dB

frequency should be > ten times the PLL bandwidth for the measurement.

The modulation bandwidth of a VCO can also be determined using the Bessel Null

technique. Apply a series of audio frequencies to the tune port of the VCO. Observe on

an RF Spectrum Analyzer and adjust the audio modulation level for the first carrier

null.

Calculate the VCO's modulation sensitivity at each audio frequency using the level and

frequency of the audio signal at the null setting.

7. The noise on one or both sources exceeds the small angle limit. For information

about verifying the noise level and recommended action, refer to Evaluating Noise

Above the Small Angle Line in Chapter 3 of the Operating Manual. For information

about measuring sources with high close-in noise, refer to Ignore Out of Lock in the

Test Mode Section of Chapter 5 of this manual.

5 Measured VCO peak tuning range exceeds 500 kHz (or 200 MHz.) The Peak

Tuning Range limit for the system is 500 kHz (or 200 MHz if an RF analyzer is configured

in the system). The Peak Tuning Range is the product of the VCO Tuning Constant

multiplied by the Voltage Tuning Range of the VCO. (If the system measures the VCO's

Tuning Constant, it will use the measured value to compute the Peak Tuning Range for

the measurement.)

Action:

Reduce the Voltage Tuning Range entered for the VCO source you are using, or

select a VCO source with a lower Tuning Constant.

6 Unable to establish quadrature. Occurs when source is under system control and

system is unable to acquire quadrature. The system attempts to acquire quadrature at

the beginning of the measurement and after it has completed a measurement segment if

quadrature was lost at any time while the segment was being measured.

Action:

Manually adjust for quadrature by adjusting the source frequency (or the Phase

Shifter if one is being used). Adjust for center scale on the HP 11848A Quadrature Meter.

Numbered Error Messages 8-9

1 2 ... 399 400 401 402 403 404 405 406 407 408 409 ... 452 453

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Agilent Technologies HP 8642A/B Specifiche Pagina 404

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