[RFI] Question: Conducted vs. Radiated Emissions

[Gary Johnson]

Jim is once again spot-on about the huge procedural error regarding how conducted emissions are measured for consumer devices. The FCC Part 15 requires only a single-ended (hot to ground, neutral to ground) measurement of noise voltage using a line impedance stabilization network (LISN). There is NO common-mode measurement required, no use of any clamp-on current sensing device. 

MIL (and some other) standards are completely different and do require proper CM measurements. Those of us who worked in EMC always brought our current probes with us when trying to track down a problem. Performance data for lights and various devices that I present on my RFI website DO have true common-mode noise data. http://wb9jps.com/Gary_Johnson/RFI.html <http://wb9jps.com/Gary_Johnson/RFI.html>

-Gary NA6O

> 
> 3) Test setups are specified in such a manner that fundamental design 
> and construction errors as important and as common as "The Pin One 
> Problem" are never seen or excited. This includes the all too common 
> failure of a "Pin One Like" problem with termination of the Green Wire, 
> and of coax connectors in CATV systems and home entertainment equipment.
> 
> And it is #3 that is, by far, the most common and most powerful 
> mechanism for coupling RFI in and out of equipment. It is, for example, 
> the most likely mechanism coupling HF backhaul data in CATV and DSL 
> systems (see page 2 of http://k9yc.com/KillingReceiveNoise.pdf and note 
> the link to work by W0QE and W0IVJ to document it). This stuff is almost 
> certainly common mode current on coax shields, coupled by Pin One 
> Problems at the point of connection, and coupled by I/O circuitry in DSL 
> systems with poor common mode isolation.
> 
> 73, Jim K9YC
> 
> 
> From: Thomas Hoyer <thoyer1 at verizon.net>
> 
> Typically conducted emissions are measured using a clamp on coupler and are lower in frequency. In the DO-160 I've been involved with, testing and the range for conducted emissions is typically 150khz to 150mhz.