NF spectrum at 150 ...
 
Notifications
Clear all

NF spectrum at 150 kHz - 30 MHz weird spiking  

  RSS

Jakobster
(@jakobster)
Active Member
Joined: 9 years ago
Posts: 9
11/08/2011 5:40 am  

Hello,

I have an NF unit in use with a preamp and an H3 probe. They are all placed inside a GTEM (which is not on), in order to minimize ambient noise. The attached image is the outcome. Can you explain why the horrible spiking there? My NF is equipped with the 30 MHz add-on.

I have also noticed that whether having the NF and the amplifier plugged in for charging or not affects the spectrum at the frequency range 150 kHz - 10 MHz quite a bit. So noise is coupling to the sensor from the common power network through the power cable. I need to have them charging though, because my measurement work takes such a long time. An ordinary LISN would fix this, because it also functions as a noise filter from the power network side, right?


Quote
Jakobster
(@jakobster)
Active Member
Joined: 9 years ago
Posts: 9
11/08/2011 9:11 am  

I find it hard to believe it's a real signal, because I have the NF, the amplifier and the probe inside a tightly closed, commercial GTEM-unit and the signal peak is not affected whether I have the power cords plugged into either of the devices or not. Also, opening the door of the GTEM doesn't have any effect on the peak. The only thing going in the GTEM is the USB cable, which goes in through a deep, small diameter hole that is intended for bringing in cables as far as I know.

What also caught my attention is that in the attached screenshot the result tab shows the peak value at a frequency of 6,4 MHz instead of the ~20 MHz where the peak occurs. In addition, the graph behaves weirdly, since in the lower graph both the sweep trace and the average trace are above max trace at the ~20 MHz. So maybe it's a bug. I would check this using LCS but I cannot get it functioning with my NF at all. It just looses the connection with it in a second.


ReplyQuote
stb
 stb
(@stb)
Trusted Member
Joined: 11 years ago
Posts: 84
11/08/2011 9:27 am  

Hello,

please go to the mcs installation directory and take a look at the script directory beneath the data directory. Rename or move the script directory to a different location, away from the data directory. Does this peak still rise ? If not - Bug fixed for the next release ;-)

PGP
Homepage


ReplyQuote
Jakobster
(@jakobster)
Active Member
Joined: 9 years ago
Posts: 9
11/08/2011 9:44 am  

That did it, no more peak. Thanks!


ReplyQuote
Share: