Can you sweep a range larger than 5Mhz?

I’m new to spectrum analysers, and looking at buying the affordable USB-SA44B, 1Hz to 4.4Ghz model. I’d like to use it to see the noise floor between 1Mhz and 200Mhz before and after a Arduino device is turned on to see how much interference it is generating.

The specs for the SA44B say:
“Resolution bandwidths (RBW) of 0.1 Hz to 250 KHz and 5 MHz”

I’m worried that this means that the device can only scan a narrow range of frequencies for a given scan, and that this isn’t the correct device for looking at a 200Mhz window.

If i’m wrong about the above, and you can chain up a bunch of 5Mhz, 250Khz or even 0.1Hz scans to capture the entire 200Mhz range in one go, my next question would be which antenna should I go for 🙂

All the best!
– John

Hi John,

Sorry for the delay in response. The SA44B can sweep a larger range than its available RBW. The SA44B can be configured to sweep any range of frequencies within its 1Hz to 4.4GHz range. At a 200MHz span the minimum RBW available will be 6.5kHz.

As for antenna, I’m not familiar with the EMI/EMC antenna market. I would imagine it would depend on what you are attempting to achieve. Are you simply trying to find/characterize interference, an RF probe might be best in this case. If you need to simulate a real EMC test, you will likely need to recreate the test setup as close as possible with a calibrated antenna. I wish I could be more help. Maybe someone else on the board could help you out? You could create a separate topic. I know there have been several users on this board with EMC experience.

Regards,
Andrew

Hi John,
I do this all the time. Its a simple comparative test so antenna choice only needs to be something that covers the frequency range of interest. It simply has to remain in the same relative location/orientation.
Simply run the SA44B with a couple of traces – one in max hold and the other in average mode across the frequency range of interest. An EMC analyser peak mode is the same as max-hold, and quasi-peak will be less than peak but not less than average.
You just need to run each test for a little while to get a build up of most of the spikes or transients.
I then export the ambient (your DUT off) and DUT active respective traces out as CSV and post process with Excel/Matlab etc. This method is usually sufficient, however it can miss burst events due to the sweep times, and if your unit has any emissions in the region of persistent signals (FM radio for example) these may be masked. You can use the same method with the real time mode though to narrow in on any peculiarities. If this is going to be a common occurance for you and your product, then, if budget allows, the BB60C may be better (Spike includes the EMC Precompliance tools for BB series).

I’d still like to see the EMC tools opened up for the SA series, just with a disclaimer around its shortcomings. I’d still have to run a compliance test anyway, it would just be more convenient.

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