Troubleshooting

RF Output Power Problems

Signal Loss While Working with a Spectrum Analyzer

The effects of reverse power can cause problems with the signal generator’s RF output when the signal generator is used with a spectrum analyzer that does not have preselection capability.

Some spectrum analyzers have as much as +5 dBm LO feedthrough at their RF input port at some frequencies. If the frequency difference between the LO feedthrough and the RF carrier is less than the ALC bandwidth, the LO’s reverse power can cause amplitude modulation of the signal generator’s RF output. The rate of the undesired AM equals the difference in frequency between the spectrum analyzer’s LO feedthrough and the RF carrier of the signal generator.

Reverse power problems can be solved by using one of two unleveled operating modes: ALC off or power search.

Setting ALC Off Mode

ALC off mode deactivates the automatic leveling circuitry prior to the signal generator’s RF output. In this mode, a power meter is required to measure the output of the signal generator and assist in achieving the required output power at the point of detection.

Use the following steps to set the signal generator to the ALC off mode:

1.Preset the signal generator: press Preset.

2.Set the desired frequency: press Frequency and enter the desired frequency.

3.Set the desired amplitude: press Amplitude and enter the desired amplitude.

4.Turn the RF off: set RF On/Off to Off

5.Turn the signal generator’s automatic leveling control (ALC) off: press Amplitude > ALC Off On to Off.

6.Monitor the RF output amplitude as measured by the power meter.

7.Press Amplitude and adjust the signal generator’s RF output amplitude until the desired power is measured by the power meter.

Setting Power Search Mode

Power search mode executes a power search routine that temporarily activates the ALC, calibrates the power of the current RF output, and then disconnects the ALC circuitry.

Use the following steps to set the signal generator to manual fixed power search mode:

1.Preset the signal generator: press Preset.

2.Set the desired frequency: press Frequency and enter the desired frequency.

3.Set the desired amplitude: press Amplitude and enter the desired amplitude.

4.Turn the signal generator’s automatic leveling control (ALC) off: press Amplitude > ALC Off On to Off.

5.Turn the RF on: set RF On/Off to On.

6.Press Do Power Search.

This executes the manual fixed power search routine, which is the default mode.

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Chapter 10

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Agilent Technologies E8247C PSG CW, E8267C PSG Signal Loss While Working with a Spectrum Analyzer, Setting ALC Off Mode
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E8267C PSG, E8247C PSG CW, E8257C PSG specifications

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