Interesting. Are you using that for radiated measurements?
I have looked into TEM cells, they can actually be bought for quite low funds now:
Lately I bought a LISN and a Siglent spectrum analyzer, so I can do conducted emission measurements. I would like to add radiated measurements to that capability also
I have this antenna, but have not verified the setup:
Kalus,
I use it for radiated work above 900 MHz. I have done radiated immunity and wire induced immunity testing at lower frequencies. It is also great for RF measurements to test radio sensitivity.
TEM cells have an upper frequency limit based on the dimensions. If you are handy and creative, you can build one yourself. Or, if you have access to a sheet metal shop. You can build it from galvanized heating duct materials. This article is pretty good. untitled (chaosproject.com)
I am contemplating a LISN. I built one a long time back. â WARNING, Always use an attenuator between the LISN and your spectrum analyzer as well as not switching things while the analyzer is connected. The spikes will blow out the front end of the spectrum analyzer. I worked with guys that did it twice!
I have a couple of similar antennas from Printed Circuit Board Antennas| Commercial and Hobby Antennas (wa5vjb.com). They work pretty well. That one should also.
It can be expensive. A collegaue of mine tested a converter without a filter, and blew the testreceiver. That was only a 50.000 USD dollar mistake 
I am going to build thios protection circuit:
Itâs just a high pass filter
The problem with conducted emissions measurements for me is the logistics of setting up a ground plane. I can do it and have done it, but itâs a PITA.
Often conducted emissions problem areas are from 150kHz to 5MHz, and in that range a big ground plane is not that important. Next time you do the measurements, try to keep the strap and lift the DUT away from the ground plane
On parts storage, I do sometimes spend up to 30minutes to find a part
Anyone dine this: take hires pictures of all the parts, let some AI SW do text recognition, so next time I need a part I can search for it in a database and the picture ID will show where the part is?
I would not be comfortable with that as my protection. The capacitor is a low impedance for transients. I always use a 10 dB attenuator. , â a $15 10 dB sma pad would work. You just have to calibrate it out in the measurements. There is usually enough noise floor margin on a spectrum analyzer.
Many commercial LISNs have limiters.
Yup. Lots of mesh from the hardware store or aluminum foil.
There are a lot of times when you can get away with out it of make something very small and crude for prescan work. You do need it for the certification tests. It really depends on the DUT and the particular test. You have to do it for a while to figure it out.
A ground plane is essential for accurate CE measurements in my experience and understanding of the test setup,. The measurement is highly dependent on capacitive coupling between the EUT and the plane (why line cord length and positioning have such a big effect on the measurement). The GP doesnât have to be âbigâ, but it should be a few multiples of the EUT dimensions and it must be the specified distance from the EUT. The GP is usually horizontal in commercial test labs, but it can be vertical, which may be easier in a DIY setup.
Not all parts are labeled with identifying information. Sometimes just a date code on things like SOTs and SMD caps usually have nothing on them at all.
The real trick is to be diligent about keeping your parts organized.
For my surface mount parts, I have them in a set of books with vinyl inserts that I can slide the tape into. I have 5 6-ring notebooks - typically a page is for one kind of part (805 resistors, for example) and all the similar pages are in one book so finding the right part is pretty quick.
My loose parts (a few big SMDs and all TH parts) are stored in small parts bins and labeled. I have to say, that isnât as easy as with the SMD books.
I keep a database of all my parts and try to update it when I use them. But, Iâm not as good at that. So when I run out, of something, I put it in a disti shopping cart. I generally have a number of things in a mouser or LCSC shopping cart. They donât auto empty them due to inactivity so when I actually place an order it picks up my needed items. A recent example, I use a lot of BSS138s. I noticed I was down to just a couple so I added 50 to my LCSC shopping cart. Next time I order from them, the BSS138s will be there.
I forgot about the vertical approach! Until recently, I always had more than ample lab space. My DUTâs were always well less than half a cubic foot and plastic-encased. There was very little capacitance to ground. The emissions were differential mode and there was a wall-wart. 10-20 dB margins were always easy to get. So, there was lots of margin going into the real test. That being said, the certified site I built and ran did meet the ANSI specifications.
The standard test is DUT distance of 80cm to the floor and 40cm to the wall (both ground planes). So the capacitance is low and normally crops up at 10MHz+, specifically as the room resonance
Anyway, I have a test coming during the coming week, so could do some reference tests with different distances and write back here
I would love to see the results!
hej @hedrickbt no worries mate! after much agonising, I bought the AD2, though would love to hear your thoughts on the DSO Nano all the same
one thing iâve been contemplating for ages is to make addressable leds that go into/behind a parts box so theyâre visible, hook it up to a google spreadsheet so i can search the part in the spreadsheet and it locates it in the space.
it suffered from feature creep and at one point became a galvo laser that could swivel and point a dot in 3d to the location or rough location of the item
for most parts i use either the cubes or the blue frame with clear box hang on the wall storage thats so common those would be perfect to add an addressable LED array too , each one could be a standalone module with an address so simpler and a serial number/mac address or something
I just bought an ESD lab chair, just to try to get the setup more up to standard
What do you guys/girls use for flooring. I am hesitant buying expensive flooring, so was thinking about just placing a 4mm aluminium plate on the floor. I may have one laying around.
About the connection to earth, was thinking a megaohm resistor, since I do not feel comfortable with a hard strapped to earth plate below me when I am working on high voltage power suppliesâŚ
So got back to this post, today I was measuring on a controller, with plenty of CM noise
Test on top of LISN (Ground plane):
Test lifted 40cm:
Seems to be no measurable difference