Forgot to add. The noise is common mode, not differential. Common mode
noise goes right through the radio out to the antenna transmission line to
antenna. Also into any capacitive grounding of radio system. This all
induces noise into the cb band. Really get real.
Some switching supplies generate a lot of noise that is in the radio
frequency area. They will power devices fine, but at the same time if you
want to receive something that some of the RF noise appears on, there will
be a problem. Some of the battery chargers around the house RF generate
noise even when not charging a battery.
Some small fans such as in a computer that work on DC have an internal
switching supply of sorts that can also generate RF noise over a wide
I built a lot of stuff for medical research, which is very sensitive to LF
noise, especially 60 Hz. I found most of the switcher supplies from jameco
were great at not producing noise in that area.
On cb I noticed what sounded like a charge and discharge, loud cracking.
Sounded like a power line leak. I went all around house finding strange
places where the noise showed up. Outside the noise was coming from power
lines. Walked up the street 300 feet, the noise was the strongest. Back at
the house I was convinced there was still something in the house. Started
flipping breakers. Found it. but didn't seem logical. My kitchen computer
area had a power strip. Look down at sears lithium power drill charger I
plugged in day before. Pulled plug, got it. The noise was not strong at the
device. I'm still wondering if neighbor has similar device up the street
where it was the strongest.
On 7/24/2012 6:06 AM, firstname.lastname@example.org wrote:
snipped bad advice.
That's exactly the point. Most devices ARE CRAP.
They're designed to work with the supplied accessories
at the lowest possible price.
The wall wart is often an integral part of the system design
for cheapo devices...especially where battery charging is involved.
I've hosted many a design review where some very smart engineer
was oblivious to the wider ramifications his "clever" design.
We know exactly ZERO about the "machine" being powered.
ANY advice on changing the wall wart is premature.
Making random WILD guesses about what is or isn't
compatible is irresponsible.
Most of the time, it's ok. But you're not the one
who suffers the consequences when it's not.
Safer to ask the OP what he's got before pontificating, don't you think?
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