Andrew
Thank you for the reply.

I did try the audio modulation and zero span options but could not find away of averaging noise over a suitable period.

To measure a noise figure under the Y factor method you need to measure a change in the noise floor when you switch on a calibrated noise source. I use a 5dB excess noise reference source so I am looking for about a 6dB change with a low noise amplifier and less with a noisy one. Spike gives the expected result using an ordinary sweep with suitable bandwidth but it is not as easy to use as the measurement receiver utility in version 2.18 software which reports the change directly.

Has anybody else used a SA44B to measure noise figures and if so how?

Richard

Andrew
Thank you for your comments.

No the problem is not related to image rejection, switching off ‘Spur Reject’ has no effect, still reading 3dB low.

The Spike measurement receiver utility (MRU) fails to synchronise to zero with white noise always reading a few dBs negative. The version 2.18 software in contrast synchronises fine with white noise.

I did a test using the Spike MRU where I inputted a pure sign wave, it synchronised fine and I then added a 6dB attenuator and got a reading of -5.981dB. So the Spike MRU works fine with a sign wave but not with noise even after you correct for the synchronisation offset.

I notice the Spike MRU lacks the options available in the old software e.g. bandwidth adjustment,FM and AM detection and gives unstable readings with noise suggesting it’s using a very narrow bandwidth. Is this the problem?

Richard

Thanks for the information, I do not think I will be upgrading to a TG124A just to be able to get a 10MHz GPS disciplined input it’s not that critical. However when not functioning as a scalar network analyser I will probably lock my SA44B.

Richard

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