[RFI] Another Solar Panel RFI System

Jim Brown jim at audiosystemsgroup.com
Fri Dec 23 17:12:31 EST 2022


On 12/23/2022 1:34 PM, Hare, Ed, W1RFI wrote:
> would probably require 30 to 40 dB lower emissions. This would add very 
> real costs and, with additional shielding needed, add weight to most 
> electronic devices. 

For many (most?) products, shielding is NOT required. FAR more 
significant are circuit design issues, like proper termination of cable 
shields and the power system "green wire," wave-shaping of power-control 
products (SMPS, variable speed motor controllers, etc.), PCB layout and 
construction. I strongly suspect that emissions from

Well-laid out multi-layer boards provide significant self-shielding; the 
key is that the "ground" layers MUST be continuous. If unbroken, they 
form a transmission line with each trace, confining fields to a narrow 
region around the trace. If broken, the trace becomes a single 
conductor, combining with whatever return circuit is available to act as 
an antenna for whatever current it carries.

Shielding between windings CAN be an issue for components like signal 
coupling transformers, like those coupling to pairs in Ethernet cables 
and other data networks, including DSL. And I strongly suspect that 
improper termination of cable shields (the Pin One Problem) is the 
primary mechanism for leakage from CATV systems. And poorly terminated 
F-connectors have a major cause of leakage since the earliest days of 
those systems.

By waveshaping, I'm talking about what Elecraft has done with their 
keying envelope to optimize readability while minimizing harmonic content.

None of which changes my assessment of the likelihood of FCC Regs 
changing for the better. :)

73, Jim K9YC







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