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Re: [RFI] Cell Phone Charger Duracell made in China

To: "rfi@contesting.com" <rfi@contesting.com>
Subject: Re: [RFI] Cell Phone Charger Duracell made in China
From: "Battles,Richard" <Battles.Richard@lee.k12.al.us>
Date: Tue, 4 Jan 2011 16:26:26 -0600
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
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: rfi-bounces@contesting.com [rfi-bounces@contesting.com] On Behalf Of 
Peter Laws [plaws@plaws.net]
Sent: Tuesday, January 04, 2011 2:25 PM
To: rfi@contesting.com
Subject: Re: [RFI] Cell Phone Charger Duracell made in China

On Tue, Jan 4, 2011 at 13:03, Jim Brown <jim@audiosystemsgroup.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
it's Micro!

Peter Laws | N5UWY | plaws plaws net | Travel by Train!
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