[RFI] Inverter RFI

[Jim Brown]

  On 10/7/2010 8:24 AM, Michael Coslo wrote:
> Good morning, all.
>
> I do a little contesting mobile. For this use, I have a laptop that I run off an inverter. It's the typical 800 watt not-quite-sine wave inverter that unfortunately puts out a fair amount of RFI. I'm pretty certain that the interference is on the power line, there may be some radiated too, but I can hear it with no antenna connected. Has anyone found any sort of solution for this sort of thing?

Two suggestions.

First, wind multiple turns of the AC cable through a #31 or #43 
Fair-Rite toroid or big clamp-on. See the Choke Cookbook and the 
measured curves in Appendix One, and use a number of turns that puts the 
resonant peak where it will cover the frequencies of interest.

http://audiosystemsgroup.com/RFI-Ham.pdf

Second, if you still have noise, add a commercial line filter, like one 
of those shown in

http://audiosystemsgroup.com/PowerFilters.pdf

My educated guess is that the choke will be more effective than the 
commercial filter, but you never know. FWIW, these inverters are well 
known to put out a lot of trash.

73, Jim Brown K9YC