Hi
The system is
receiver (~1 MHz)-cable-Spectrum Analyzer
When cable ground is connected to the receiver ground I have great received noise
When transformer was used between cable and receiver the noise was less but was
What is the common practice in such cases?
What is the best solution?
Ground isolating transformers are needed sometimes when using/measuring with equiments with GNDs which may be on a very different potencial, and may gather with their grounds (ground loops) low and high freq signals and noises.
There are cases, when even the isolation transformer does not help. Then you should find some different measuring setup.
What kind of setup you use ?
What is the input impedance of your spectrum analyzer? where exactly are you trying to measure? what is the output impedance of the point you're trying to do the measurement at? some other point that comes in mind is that if your analyzer has a DC coupled input, it might change the bias point of your output stage transistor...
I'm just a little curious. Hope the questions are not too stupid. Are you talking about conducted emission problems or radiated emissions? Is it broadcast or line cord? If its conducted are you using a LISN? What standard are you trying to reach?
When working on electromagnetic compliance the standards look for a couple of different things. In terms of the amount of noise that you generate they can come in a couple different forms. One way is broadcast - radio frequencies propagating through space. Another is conducted emissions and these tend to be the amount of noise your product generates and then passes back along the power cord or some other cable. These emissions can travel back into the local building grid and disrupt other machine. They can also be conducted out the cable and then broadcast like an antenna if the frequency is high enough. Hope that helps.
as for the FLOEMC I am not familiar with this software but based on the description I would assume it is a simulation software.