nesesu wrote:
On Wednesday, August 8, 2012 2:29:52 AM UTC-7, William Sommerwerck wrote:
I don't know about the USA but the rest of the world has largly moved
to regulated SMPS for small device wall warts. And they generally
even suport the USA voltage too (Wot is it 120 volts) ;-)
Conventional external power supplies using bulky 50/60 Hz line
transformers have largely disappeared, as the parts used in switching
supplies have become less-expensive. Most products come with tiny
high-frequency supplies that are not only regulated (regulation is a
native feature of switching supplies), but will work on any line from
90V to 250V. This allows the manufacturer to have a single inventory.
The same supply is shipped to every country, with only a simple plug
adapter (where needed).

FWIW, I have found that many 'compliant' SMPS 'wall warts' cause severe
radio interference on the BC band and SW bands, but much less so on the
FM band. Conducted and radiated emission standards for these units are
generally fine unless they are connected directly to a receiver [where
the PSU is effectively in series with "Ground" ].

Neil S.

To power a cb radio, I had to add 3 more ferrites plus extra turns through
them to get acceptable results. To get low capacitive 60 Hz feedthrough,
you need to ground one output leg. That was necessary when using audio or
medical devices.

Greg