Greg wrote:

Here's a line of power inverters marketed to photographers, but possibly of
interest for use with radios. They offer "pure sine wave" inverters as well
as cheaper switching power supplies.

What's the difference, in layman's terms, between sine wave and switching
power supplies? What are the pros & cons for practical applications?

I've always wondered if the switching power supplies, like the Radio Shack
models, that convert 120VAC to 13VDC, are appropriate for radios.

Thanks,

Greg

They are "Pure sine wave" only when fed into a purely resistive
load. When you power a radio with one, the power diodes at the input
create a nonlinear load: Very heavy at the peaks and no load at lower
voltages. The inverter would have to be run at a very small percentage
of its rating along with some other loading or through a resonant line
filter to help even out the load to the inverter.


A lot of cheap "Wall warts" are built without caps across the
rectifiers which cause them to generate a lot of RF noise and carry it
right to the radio with the DC power. I've got a couple hundred Wall
warts and very few have the extra caps to stop the RF problems. All you
have to do with most of them is plug it in close to a radio and you'll
hear some noise but it's a lot higher if you power the radio from it.

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida