Ni 5663 Vector Signal Analyzer

[leomdma]

Hello! I use the Ni 5663 Vector Signal Analyzer. When signal analyzer reading amplitude from generator, it does not match with amplitude by generator.  What could be the problem?

[leomdma]

and one more question, the ni 5601 module from vector signal analyzer, has electrical and mechanical attenuators, and i know that in automatically mode, used both types of attenuator. What is the algorithm works attenuators? When used mechanical attenuator? After some level of signal or otherwise?

[AirFrantz]

How far off are the readings from your VSA from the expected output power of the generator?  How are they connected?  If you are seeing less than expected on the VSA, this is most likely due to path loss (cabling/connections/instrument front ends) which would be completely normal.

As for your question about attenuation, I found the following in the NI-RFSA Help:

Increasing Measurement Speed by Disabling the Mechanical Attenuator

By default, NI-RFSA uses a mechanical switch to activate a 16 dB RF attenuator at certain reference levels. The mechanical switch provides superior distortion performance at the expense of slightly slower switching time than the other RF attenuation steps, which use electronic switches.

The following table approximates the reference levels above which the 16 dB RF attenuator is used. The exact reference levels differ for each downconverter.

Frequency	Reference Level
<120 MHz	>9 dBm
≥120 MHz, <3GHz	>5 dBm
≥3 GHz	>16 dBm

If your measurement application requires faster measurement speed than the mechanical attenuator provides but can tolerate reduced measurement accuracy, you can replace the 16 dB attenuator and mechanical switch with 16 dB (equivalent) attenuation and electronic switching. The faster switching speed of the electronic switch provides up to 3 ms improvement in measurement time (and approximately 0.5 dB reduction in measurement accuracy).

To disable the mechanical attenuator, set the Mechanical Attenuator Enabled property to Disabled or set the NIRFSA_ATTR_MECHANICAL_ATTENUATOR_ENABLED attribute to NIRFSA_VAL_DISABLED.

To return to default operation, set the Mechanical Attenuator Enabled property to Enabled or set the NIRFSA_ATTR_MECHANICAL_ATTENUATOR_ENABLED attribute to NIRFSA_VAL_ENABLED.