- ghuxtable January 4, 2021 at 5:40 pm
I have access to a SA124B which I have yet to learn to use (my RF experience is pretty limited) but need to test some gear for compliance to EN61000-6-4. Attachment has the relevant limits.
Presumably with a suitable antenna or antennas I can make these measurements?
I assume that the gain characteristics of the antenna(s) is somehow input into the Spike software and then compensated for?
Is ‘Quasi-Peak’ a mode that can be measured with the software (and what exactly does Quasi mean)?
Cheersghuxtable January 4, 2021 at 8:31 pmghuxtable January 4, 2021 at 9:02 pm
I have also noticed in the Spike manual, section 4.8, that ‘Precompliance measurements are available for BB series and SM series devices’. This answers my other query which I need not now ask – that being why was ‘EMC Precompliance’ greyed out and not available in my installation of Spike.
So why is it that the SA series devices do not have this option?
ghuxtable January 4, 2021 at 11:51 pm
- This reply was modified 2 weeks, 2 days ago by ghuxtable.
At risk of revealing my limited knowledge…
Attached is the test lab result I am trying to replicate.
How can I set up Spike to replicate the scale (dBuV/m) for example?
And show same limit lines?
Showing my lack of experience here.Andrew January 5, 2021 at 9:01 am
The precompliance measurements mode in Spike would allow you to setup a measurement like the one in the picture you provided, with one limitation, in that we only perform QP measurements at a single frequency. Ideally you would sweep with a peak detector, and check troublesome frequencies with the single frequency QP detector we provide. The single frequency QP detector is only available in precompliance mode.
The SA44 and SA124 are excluded from the precompliance measurements due to their lack of hardware image rejection. Using the SA124 for precompliance measurements will introduce false positive spurious image responses for every real signal input. Without a good understanding of the SA124 architecture it will be difficult to interpret the results.
At this point we do not have plans to enable precompliance measurements for the SA124. The BB60C is the most affordable analyzer we sell with precompliance mode enabled.
You can use the path loss table functionality to enter the antenna factor table. This will be applied for both sweep and precompliance measurement mode. Units would then be in dBuV/m. In precompliance mode, dBuV units are default, in sweep mode, you can select dBuV from the reference level control.
Let me know if you have follow up questions.
Regardsghuxtable January 5, 2021 at 5:47 pm
I am also having difficulty setting up the limit lines.
For example in the attached screenshot I have used -67dB to generate a 40dB limit line. I see that the Limit Line points are specified as ‘dBm’ but what does that mean? If it means dB relative to 1mV then I would subtract 60 to convert from dBuV to dBmV (40dBuV would become -20dBmV). How does 40dBuV/m convert to -67dBm ?ghuxtable January 6, 2021 at 12:30 am
Can you also please confirm that my understanding and implementation of the antenna factors is correct (by way of comparing the attached csv with the antenna spec’s also attached)?
Andrew January 6, 2021 at 9:43 am
- This reply was modified 2 weeks, 1 day ago by Andrew.
You can convert to dBm from dBuV by simply subtracting 107dB.
Try decreasing your reference level. The devices maximum sensitivity is ~50dBm or 57dBuV. Your noise floor will drop ~30dB from its current position. This will get you very close to the pictures in the other software you provided. Decrease ref level to 60dBuV or 55dBuV. Any lower than -50dBm and you won’t see any improvement in the noise floor.
Your path loss table values appear correct. Our software will linearly interpolate between your points. If you need more resolution you can also add more points later.
Regardsghuxtable January 6, 2021 at 3:42 pm
Yes I see what you mean about the noise floor. Why is it that the noise floor changes? I guess this has something to do with the amplifier circuitry and the sensitivity / gain required for the new reference level?
Is there a way to control the scale of the horizontal frequency axis so that it is logarithmic rather than linear?Andrew January 7, 2021 at 7:47 am
Yes, changes in the reference level affect sensitivity, which change gain and attenuation of the instrument. A lower reference level implies you will be making measurements on smaller signals, in which we increase the sensitivity.
In standard sweep mode, linear scale frequency is the only scale possible. There is no way to plot on a logarithmic scale outside of the precompliance mode. I apologize for the inconvenience.
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