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Author Topic: RFI Power Cords with filters  (Read 3022 times)
WB4BYQ
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Posts: 180




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« on: January 19, 2010, 06:13:38 AM »

Please look at these power cords that have RFI filers built into the cord.

http://www.emceupen.com/

these cords could solve at lot of problems.

richard
WB4BYQ
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N3OX
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« Reply #1 on: January 19, 2010, 08:19:03 AM »

Those are interesting... one of my computers could really benefit from a couple of those... as it stands I put a Corcom filter in a box ;-)

You tried to obtain small quantities yet?
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
WX7G
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Posts: 6332




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« Reply #2 on: January 19, 2010, 11:32:27 AM »

Interesting cords. The model NA101 is the one to try as it incorporates Y-caps.

The thing that can render these filter cords ineffective for the common-mode RF issues amateurs have is that the common-mode RF currents are present on all three conductors; line, neutral, and ground. These line cord filters provide common-mode filtering on the line and neutral only.

They are designed to enable a product to pass FCC and EU conducted emissions EMI tests. The real world situation is a bit different in that rather than having an EMI ground at the end of the power cord it may be 50 feet away at the building AC service entrance.

So, the trick of running the power cord thru a ferrite core provides an increased common-mode impedance for all three wires.
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WX7G
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« Reply #3 on: January 19, 2010, 11:34:34 AM »

I should add that these cords are designed to help a unit pass conducted radiation testing and conducted emission testing. They do not help with radiated susceptability testing, and it is that that mimics the amateur radio EMI environment.
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WB4BYQ
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Posts: 180




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« Reply #4 on: January 19, 2010, 01:18:21 PM »

I have not tried to order any,  not sure who sells the cords.  have not called the company yet either.  WX7G does have a good point of view on the engineering of the cords.  i just wanted to post the find.

i found the information in a samlex swithching power supply papers with the supply.  i will quote what they say.

"Following additional guidelines may be followed to reduce the effects of RF noise:

Use additional appropriate AC radio frequency interference (RFI) power line filter immediately before the ac input to the power supply.  Recommended:
Corcom Inc. (www.cor.com) "Q" series.  Filtered, ferrite coated cord set (www.emceupen.com) is another source.  These cord sets, with integral line interference filters, reduce common and differential mode interferences over a wide frequency range.  Because they are shielded, they are also effective against radiated interferences.  In addition to the built-in filter networks, the cable conductors are coated with an RF absorbing ferrite compound.  This provides additional attenuation at high frequencies that is lacking in most reqular LC filters.  The RF
absorption of the ferrite-coated cable avoids resonance's at high frequencies, reducing the conducted and radiated RF noises even further."

Maybe some one can tell us if they work.

richard
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WX7G
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« Reply #5 on: January 19, 2010, 03:35:26 PM »

I mean to say the cords are designed to enable a unit to pass 'conducted emissions' and 'radiated emissions.'

Consumer gear is tested for radiated susceptibility at 3 V/m. Hams often have to solve problems where the fields are >100 V/m. This is where common-mode filtering - ferrite - on all three wires (line, neutral, and ground) can be helpful.
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