EMC problem in a receiver-cable-Spectrum Analyzer system

[Grig]

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?

 

[g579]

Re: EMC problem

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 ?

 

[Grig]

Re: EMC problem

What is "measuring setup"?

 

[sinip]

Re: EMC problem

What is "measuring setup"?

Instruments and procedures used to take certain measurement.

 

[Grig]

Re: EMC problem

The procedure is

Receiver(500kHz-1500kHz and ferrite antenna)+cableRG58(~10meter)+Spect Analyzer

and see spectrum
also receiver demodulates AM and i can check sound

When Spect Analyzer is connected with cable the sound is very noisy
When Spect Analyzer is not connected the sound is noiseless

 

[3dandyw]

Re: EMC problem

hey you can still try to make a model and do a simulation: FLOEMC or MICROSTRIPES (3D EM Solution)

AW

 

[bamdad]

Re: EMC problem

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...

 

[dfullmer]

Re: EMC problem

Hi guys,

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?

Regards

dfullmer

 

[Grig]

Re: EMC problem

Hi
What is conducted emission?

Added after 52 seconds:

What is FLOEMC?

 

[dfullmer]

Re: EMC problem

Hi Grig,

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.

Regards,

dfullmer