Rick (W-A-one-R-K-T) wrote:
I have a so-called "modified sine wave" inverter that is connected to 200+
amp hours of deep discharge battery located in about the center of the
house in the basement. About a 30-foot length of #14 wire goes to an
outlet box in the shack, down on one end of the house, and provides 110VAC
(of a sort) when the power is off and I don't feel like hauling out the
generator. :-)

Trouble is, whenever I turn on the inverter it spews harmonics all up and
down the HF band and makes it difficult to impossible to hear weak signals.

I realize that a pure sine wave inverter would mostly alleviate this but
that's not gonna happen any time soon... meanwhile is there a filter I can
apply to the output of the inverter to round off the corners of the
modified sine wave (which is really nothing but a stairstep square wave)
and eliminate the worst of the harmonic noise?

Thanks...

Shield the inverter and the battery together,
put an ac filter made for computers on the output of the inverter were it exits
the shielded enclosure, and ground the shielded enclosure to earth. You should
see a big difference in noise...

Bob N9LVU