Hi! (What is the trick to get the pictures in line with the text? OK, thanks Tim! Is it possible to keep them at default tumbnail size and only load to full size by mouseclick?)
in the meanwhile my BNC-sockets arrived from china as I missed to order the cheap TE 5-1634503-1 from Mouser when I ordered all other components for Mate and Lisn.
![](https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/?action=dlattach;attach=1177376)
I measured the transmission behavior with Scope Bode Plot function:
When measuring it from Lisn2 In to CM Out it's like this: (result -6dB)
![](https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/?action=dlattach;attach=1177380;image)
Same but leaving DM-port unterminated: (result -9dB)
![](https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/?action=dlattach;attach=1177384;image)
When measuring from Lisn2 In to DM Out: (result -6dB)
(seems there is some signed integer treated as unsigned somewhere in the MSO5000 Bode Plot script when phase flips over 180°)
![](https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/?action=dlattach;attach=1177388;image)
When measuring from Lisn1 In to CM out: (result -6dB)
![](https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/?action=dlattach;attach=1177392;image)
From Lisn1 to DM out: (result -6dB)
(Why does it shows a higher edge frequency? Is there an impedance discontinuity because of too much twists in the copper ends near the solder pads? Or should I remove the last winding form CAT5 because it fills the hole in the core and coulpes in to the other side?)
![](https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/?action=dlattach;attach=1177396;image)
Seems that these cores are close to the TDK ones, are they?
When measuring the whole path from DUT+ and DUT- through
the forums final double Lisn with -10dB attenuators inside and
through the Lisn-Mate to CM out I've got the following results:
(I guess it is -6dB because the signal was divided by 2 when feeding it to DUT+ and DUT-,
but why isn't it -10dB-10dB-6dB-6dB=-32dB)
![](https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/?action=dlattach;attach=1177400;image)
When measuring the whole path from DUT+ and DUT- to DM out: (-3dB ?)
![](https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/?action=dlattach;attach=1177404;image)
There first I thought something went wrong, but on the other hand it reflects somehow the overlay of both DM-plots above.
P.S.: I had have only one BNC termination and used a 25cm BNC to SMA cable with a SMA termination at the end for second termination. For third termination I simply connected the Lisns SMA output to the port. You find the termination type in the file names for each plot.
For noise measurements I am still wondering how I have to set my correction level in the spectrum analyzer with the different setups:
1 Lisn with -10dB attenuator no mate +10dBµV (add 10dB noise)
2 Lisn with -10dB attenuator no mate +16dBµV
2 Lisn with -10dB attenuator mate DM out, CM terminated +3dBµV
2 Lisn with -10dB attenuator mate CM out, DM terminated +6dBµV
This is what the scope plot tells me, but the scope shows a dB relation between two peak ac voltages, how does it fits to the absolute dBµV ?
I guess as this is also relation of voltage to 1µV, it fits very well, right?
But as the CISPR standard does not distinguishes between CM and DM and only measures with two Lisn the output of one of them
do I have to compensate anyhow or is the -6dB included into the standard?
And as Jay_Diddi_B writes in post #21 that this Mate stuff is only for interest on the way to find the noise source but with correct design could stay in the setup,
then I should have to compensate the SA in the same way as without Mate like this:
1 Lisn with -10dB attenuator no mate +4dBµV
2 Lisn with -10dB attenuator no mate +10dBµV
2 Lisn with -10dB attenuator mate DM out, CM terminated +10dBµV
2 Lisn with -10dB attenuator mate CM out, DM terminated +10dBµV
Please correct me if I am wrong!
For me it's same: "Also, I have no idea what I'm talking about."
And: "I appreciate all of your guidance (and patience with me)."
Kind Regards,
Hanno