[RFI] SOLAR INSTALLATION PROS/CONS

[Jim Brown]

Tests performed in labs are one thing, and by their design, they often 
fail to expose fundamental problems. One of the most common is failure 
of the Green wire to be properly bonded to the shielding enclosure of 
the noise source. When this happens, the noise is ON the green wire, and 
goes right past any traditional line filters.

There's also the issue of defining common mode. For EMC testing, it's 
the voltage between neutral and Green, and traditional line filters are 
DIFFERENTIAL filters -- they are not applied to the Green wire, they are 
referenced to it! From an RF point of view, common mode is the algebraic 
sum of current on all of the conductors of a cable, and it is that 
algebraic sum that RADIATES. The only thing that a power line filter can 
do, if properly applied at the noise source, is to bond the green wire 
properly, and with what my EE profs called a "zero length lead."

As to the DC circuit -- all parts of it MUST be treated as a 
transmission line run with twisted pair, as I noted in an earlier post. 
It must be treated this way because it's NOT DC, it's DC modulated by a 
rectangular wave, and, to minimize dissipation, usually has the fastest 
rise and fall times practical, which maximizes harmonic content.

There is a better way -- mathematically shaping of the rise and fall 
transitions like Elecraft introduced with their K3 transceiver to 
minimize key clicks. Designer Wayne Burdick describes it as "sigmoidal" 
or a "raised cosine function."

Bottom line -- this is a SYSTEM DESIGN problem that includes overall 
system architecture, the equipment used, and its installation. And as 
usual, the chain is as strong as its weakest link.

73, Jim K9YC

On 5/23/2021 6:03 PM, Carter, Michael wrote:
> For those who would like to know what are the
> conducted and radiated RFI limits in the EU and
> U.S., this report (beginning on p. 11) provides
> a nice summary: