David ) writes:
A low B Flat on a portable synthesiser coupled to a 12 volt amp?

Well that's the general idea, a sine wave oscillator feeding an audio
amplifier.

A square wave inverter is only on or off, so efficiency is better.
But of course, it has lots of harmonics from the square wave, which
of course can interfere with reception. There's also the issue of
whether the equipment that is powered from it can handle it. The
square waves may not be good for specific pieces of equipment.

I"m not even sure what this is about. A shortwave radio, if it
uses an external power supply, is not going to need an inverter.
You either power it with batteries (a separate stash, or filtered
from a car battery), or an AC adaptor. Current demand is not
so high that a regular transformer power supply will be too bulky,
so there's no need for anything fancy.

The only case one needs an inverter for shortwave receivers is if
the receiver has a built in supply, and now way of powering from
an external DC supply.

Michael