EMI noise in the 50-500 kHz range

Unanswered Question
Sep 8th, 2010

Could a wireless IP phone system cause noise in this range?

I'm working with a test device that is built to pick up signals in the 50-500 kHz range and the device is now picking up "external noise" that severely affects the reliability of the tests.

The noise seem to have a periodic nature of 30-32 Hz and is nearly attenuated in one direction as well..

The user claims that the noise appeared whenever they installed a Cisco IP phone system.  They are using 7925 wireless phones.

I have this problem too.
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Kayle Miller Tue, 10/05/2010 - 13:42

Stephen,

    

     If I have learned anything from years in the RF business I have learned anything is possible, in terms of your issue, I find it highly unlikely that the phone would produce EMI in the range you specify and at the strength that it sounds as though it's doing. With that being said it's possible I've never had the equipment on hand to test a 7925 that low, so I can't say from my perspective definitively oneway or the other on it.

     I'd suggest they try shutting off the phones and see if the noise source goes away.

Hope this helps.  Please rate useful posts.

skendrish Fri, 10/08/2010 - 08:10

Thanks for the input.  The sensor on our equipment is basically an antenna for EMI in the 10 - 750 kHz range.

Although the sensor is directly coupled with the steels we test, any strong external source can still get into our processing.

I'm also seeing that it's very directional and exists in certain areas of the facility only.

Since I'm not a signals eingineer, etc. Is there anyone that we can contract to go into our customer's facitlity and characterize the noise and it's source or sources?

Our engineers told me once that the equiment to do this is quite expensive for us to procure.  Are their services for this?

I'm located near Pittsburgh, PA USA but our customer facitilty is in Kitchener, Ontario Canada.

I suppose that we could use our test sensor to find the highest source of the noise, but the system isn't as portable as we woudl like it to be.

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