Hey Jay, did you happen to do any VSWR readings on your TEM cell? I am curious how you decided to move the septum up a bit without affecting the characteristic impedance too much? In the near future I will need to test an "electrically large" DUT and I saw in some papers that the device being tested should generally be <1/3 of the septum height otherwise you through off the characteristic impedance of the cell.
I suppose I can do some impedance measurements and throw in my aluminum enclosure to see what it does without any active electronics in it.
I moved the septum to increase the working height in the TEM cell.
The width of the septum was adjusted to obtain a nominal 50
I did measure the impedance using a TDR. The TEM cell was connected to the TDR with a piece of Goreflex cable that was known to be 50
The TEM cell was open at the far end.
The measured impedance is about 58
I also measured VSWR with the TEM cell terminated with a 50
load.
The bottom of the screen is 0.6, so the VSWR was better 1:1.6 over the range 300kHz to 1GHz with a small exception which is 1: 2.2, indicated by the marker.
I did not bother to try and correct any of this, because when you put the device under test in the TEM it will change the impedance.
I use my TEM cell for relative measurements.
Regards,
Jay_Diddy_B