[RFI] RFI Question

Jim Brown jim at audiosystemsgroup.com
Fri Feb 12 14:33:21 EST 2021

That feeling is correct. Simple way to study it. Build a simple NEC 
model and compute the response for a range of frequencies, one after 
another. Write down the field strength at the same horizontal and 
vertical angle. Do the same for every other horizontal and vertical angle.

Time consuming?  Sure, but you'll learn a lot. Oh -- and when you build 
that model, be sure to include signal return, whatever it is. Like the 
green wire running through the home that houses the noise source, maybe 
cable TV.

BTW -- there are very few devices that produce energy uniformly across 
the spectrum. The vast majority of electronic sources are the harmonics 
of switch-mode power supplies, variable speed motor controllers, or 
clocks for microprocessors. These are anything but uniform, showing up 
as "humps" of noise at intervals of 10-20 kHz, or steady carriers that 
don't move. The nature of these harmonic sources is that they get weaker 
with increasing frequency.

73, Jim K9YC

73, Jim K9YC

On 2/11/2021 11:02 PM, Tony wrote:
> I have a feeling it's not as simple as that. 

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