Discontiunity in noise measurement

I’m looking at the noise from my amplifier circuit with the SA44B, but I’m getting a strange discontinuity around 16MHz. I run the same test with a different spectrum analyzer and there is no dicontinuity. Overall they look similar, but why is there a 3dBm drop at 16MHz? See attached data sets.

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Hi Elieser,

At 16 MHz the SA44B switches over to a more sensitive IF which is why you see the step in the amplitude.

Regards,
A.J.

Can that be calibrated out? My plots look horrible with a sharp 3dBm drop right in the middle . .

You can turn image/spur rejection off. This will force it to stay in the higher noise state, but also lets spurious signals through. Note that with the SA44B there is a 3 dB correction for broadband noise, as the software image rejection cannot filter out noise at the image frequency.

The BB60C can perform this measurement without the correction.

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