Hello, Bob.
Thanks for your explaining. I know that this is a complicated thing, but I bought? "tinySA Ultra"? to be able to find out if my developments are in safe distance to allowed limits of electromagnetic noise, or if (and where) my DUT excesses this limits.?
This saves a lot visits for pre-compliance testing and therefore lots of money (-> the reason why I bought the ULTRA for).
As far as I know, it is legal to do a self-declaration that a device is complying, but then it - of course - indeed has to be compliant. But knowing that my DUT is far below allowed limits before even doing a first pre-compliance test is always a good start.
So I would do the testing by either moving to a location some kilometers away from buildings and mobile phone antennas, etc., move to a deep parking house, or similar, ? and do two scans:
One without my DUT turned on (recording the environmental noise), and another one with my DUT turned on (recording environmental noise + DUT's noise). Or I build a Faraday cage using a fine and grounded metal mesh and do the above inside the laboratory. (will also reduce external influence) before.
The difference should be my DUT then, right?? As my developments usually are small devices for automating or recording something, they are often battery operated. If not, a certified power adapter with cable length shorter than 1m makes life also lots easier.
?
This will at least give me information on noise generated by the DUT.?? Doing this math without an automated script is a horrible job, because tinySA (Ultra) by itself is not really easy to use (at least for me).
If additional tests are required (i.e. the Conduction Emitted Tests), this is another part I will have to do separately. But most important is the direct emission to air, because I often use plastic enclosures and digital electronics. Well, I already try to always use Microchip PIC controllers with internal oscillators, this drastically reduces radiation, but it is still digital, with lots of square waves therefore.
?
