I had a neighbor that had a no name brand cell phone charger that his son's
girlfriend would bring with her when she would visit the home. terrible noise
on 40 meters. traced it with my portable sony short wave receiver to their
home across the street and down one house. the neighbor was very helpfull by
cutting the power ac breakers one at time till we found the breaker that we
needed. i made some filters with small corcom 5 amp emi/rfi filters in small
plastic box for projects with heavy duty two wire extension cords by cutting
the plug in about 2 feet from the end and drilling holes in the box, soldering
the two wires to the filter, making sure that the polarity was correct and
sealing the ends with silicon. i plug the two wire charger in the plug of the
cord and no noise at all. i have made several of these filters with one
corcom, two corcom, three corcom. fix my son's no name brand dell laptop
charger that was causing rfi on 160, 80, 40. it is a two wire plug.
if you do not filter the ground on a three conductor the rfi will flow around
the filter on the ground, that is were i use a ft-240-31, or ft-240-43, or
ft-240-77 to wind all three conductors.
From: firstname.lastname@example.org [email@example.com] On Behalf Of
Peter Laws [firstname.lastname@example.org]
Sent: Tuesday, January 04, 2011 2:25 PM
Subject: Re: [RFI] Cell Phone Charger Duracell made in China
On Tue, Jan 4, 2011 at 13:03, Jim Brown <email@example.com> wrote:
> One of the most problematic elements of chargers like this is that the
> connector that connects to the cell phone is non-standard and the
> charging voltage and current are unknown. This makes it a bit of a
> challenge to home brew something to replace it.
Mobile manufacturers have decided to standardize on Micro-B USB
connectors. Since they are also usually the USB connector for the
phone and thus are USB-standard, that pretty much limits it to 5 V dc.
The USB spec is limited to 0.5 A draw, but that's from a computer,
not a wall wart, so I imagine the phone could draw more from the
wall-wart if that was needed. See, for example,
When will all manufacturers/models actually ship phones with those
connections, who knows? But it's in their interest so it probably
won't take too much longer.
I noticed that the Tecsun PL-606 LW/MW/SW/FM rig I just ordered from
China doesn't even come with a wall-wart at all (probably avoids
Customs issues) but has a USB jack for charging/powering. Hopefully
Peter Laws | N5UWY | plaws plaws net | Travel by Train!
RFI mailing list
RFI mailing list