SWL/RFI noise source discovery
 

After looking for 2 weeks for the source of
noise that was producing an s-5 noise from
3 to 8 MHz on the dial of my older Icom I
found the source. My Dewalt cordless drill
drop-in battery charger. Apparently this charger
uses a rather harmonic-rich power supply and
charging circuit. Remove the battery and unplug
the charger and the noise disappears. Any of
you having a Dewalt cordless drop in may want
to check this also.

I just discovered the same thing yesterday: both my cell phone charger
and my Rigid cordless drill charger spew incredible amounts of RFI. I
suspect today's "smart" chargers are almost all big RFI emitters.
Ditto my laptop AC power coverter!

"brass eyelets" wrote:
After looking for 2 weeks for the source of
noise that was producing an s-5 noise from
3 to 8 MHz on the dial of my older Icom I
found the source. My Dewalt cordless drill
drop-in battery charger. Apparently this charger
uses a rather harmonic-rich power supply and
charging circuit. Remove the battery and unplug
the charger and the noise disappears. Any of
you having a Dewalt cordless drop in may want
to check this also.

On 16 Nov 2003 15:58:33 -0800, (Marc A. Murison)
wrote:

I just discovered the same thing yesterday: both my cell phone charger
and my Rigid cordless drill charger spew incredible amounts of RFI. I
suspect today's "smart" chargers are almost all big RFI emitters.
Ditto my laptop AC power coverter!

Damn cheap, poorly designed switching power supplies! I replace them
with analog supplies rated the same or higher current. Analog
float-chargers aren't that hard to build, either.


"brass eyelets" wrote:
After looking for 2 weeks for the source of
noise that was producing an s-5 noise from
3 to 8 MHz on the dial of my older Icom I
found the source. My Dewalt cordless drill
drop-in battery charger. Apparently this charger
uses a rather harmonic-rich power supply and
charging circuit. Remove the battery and unplug
the charger and the noise disappears. Any of
you having a Dewalt cordless drop in may want
to check this also.

On Mon, 17 Nov 2003 01:04:39 GMT, Herbert West
wrote:

Damn cheap, poorly designed switching power supplies! I replace them
with analog supplies rated the same or higher current. Analog
float-chargers aren't that hard to build, either.

Yes, but they're often quite efficient. The problem is the
certification idiots. These manufacturers put just enough ferrite
material in these devices to meet the specification, but not enough to
be truly effective.

An easier and possibly cheaper solution might be to put ferrites on
the power cords going in and out of the charger. If it's a wall wart,
put the wall wart on a small outlet strip and put an RF block
(ferrites and three high voltage bypass capacitors) on the strip
before it goes in to your house.


Jake Brodsky, AB3A
"Beware of the massive impossible!"