[RFI] GE Microwave

[Jim Brown]

On 8/28/2012 6:15 AM, Hardy Landskov wrote:
> Corcom filters have a common mode choke on the hot and neutral in 
> their filters but not on the green wire. What is your take on that?
> 73 Hardy N7RT 

Useless if the noise is common mode on all three conductors unless the 
filter is effectively bonded to the noise source by a very short 
conductcor.  I have a bunch of their filters here, bought surplus. Used 
to own their stock when they were a public company.  Good company, good 
products.

One root of the problem is the power systems equivalent of The Pin One 
Problem -- that is, the noise source is not properly banded to its 
enclosure, so the noise is common mode on all three conductors. A simple 
example: I own three Astron linear supplies, all three of which have the 
same fault -- the green wire and circuit common go to the chassis lug of 
an old fashioned terminal strip, which is insulated from the chassis by 
PAINT.  A simple test with a DC ohmeter shows no continuity between the 
green wire and the chassis. These products are in violation of every 
building code I know of, and should not have passed final test. And such 
faults are NOT unusual.  If this product was a switching power supply, 
the lack of that bond would cause line cord to radiate a lot of common 
mode noise!

Another root cause is what WE call common mode -- all three conductors 
-- is different from what the power industry calls common mode -- noise 
between neutral and green.

73, Jim K9YC