100kHz on Signalhound display

I’ve been doing noise figure measurents successfully with the SignalHound. However, I have a 100kHz signal on the trace I’m trying to measure. I can work around this, but is this a known problem with the SignalHound or a fault on my unit?
best wishes,

Ed Long

Eduk,
The SA44B works by capturing 200 kHz patches of spectrum and processing them. There seems to be some 200 kHz periodicity. I noticed that the peak-to-peak periodicity improves for the stronger signal, so it looks like what you are seeing is the IF filter shape on the SA44B’s noise level.

Because your RBW is 100 kHz, the software has a hard time correcting for IF flatness. If you reduce your resolution bandwidth to 30 kHz, the software will have an easier time correcting the IF flatness, and this ripple should be reduced.

I think the following is quite a useful follow up. I have set the RBW to 30kHz and the VBW to 3kHz. I have averaged 100 sweeps. The trace shows the Y-factor from our amplifier with an RFDesign RFD2305 noise diode with an ENR of 5.7. Most of the 100kHz/ 200kHz is gone and we get a fairly flat noise trace. The noise figure is calculated from the ENR and the Y-factor and comes to 1.32dB. A test house measurement of the same amplifier gave a noise figure of 1.27dB. This figure was measured on HP346B noise figure meter.

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