About a month ago I posted an article about my "modified sine wave"
inverter and how to get rid of the strong noise it generates across the HF
bands.

I got several helpful responses and I thought you might be interested in
the results.

I ordered a Sprague 20JX5306A line filter from HSC Electronic Supply
(www.halted.com), cut a three-wire extension cord about four inches from
the plug end, and inserted the filter.

It works quite well. There is still some noise, around S2 or S3 as
contrasted with S8 to S9+ that it was before. There are some other things
I can do such as enclosing the inverter and filter in a grounded metal
box. But, all in all it works acceptably as is.