[RFI] Apple and Motorola Wall Chargers

[Dale]

Michael,

A "quiet" switcher (that term should be classed as an oxymoron) may well not disturb your radios or other equipment, but it sure can raise havoc with 160m and AM b'cast band reception.  I have factory original OEM chargers for my Samsung cell phone and Icom IC-91A HT.  Both wipe out reception on the AM band if the charger, device being charged, or cable from charger to device is located any closer than about 5 feet to the AM radio.  In my vehicle, the mobile charger wipes out the AM band in the car radio, which is a bummer when wanting to listen to news or a sports event.  I don't know if that is due to radiated coupling between the charger's output cord and the vehicle's vertical rod antenna (about 3 feet away, on the passenger side fender) or conducted emissions on the 13.6 VDC power bus.  Bad news, either way.  

With the ever-increasing use of Li-Ion batteries in portable devices, use of old-style linear chargers (meant for Nicads) is problematical.  The good news is that many of the switcher/chargers are "smart" chargers that properly control charge rates for the batteries.  That smarts is often buried within the switcher driver chip, so it is not feasible to separate the power supply function from the charging circuitry.  Let's face it: switchers are here to stay for a long time.

Actually making your own linear DC power supply to operate a device is not difficult - you can find filament transformers, diodes, filter caps, and linear regulator ICs in various output voltages, but the problem comes when you need to limit charging current to a battery pack.  That can also be true when "recycling" a charger wall wart from one device to another. 

73, Dale
WA9ENA        


-----Original Message-----
>From: Michael Coslo <mjc5 at psu.edu>
>Sent: Aug 15, 2013 7:56 PM
>To: Rfi List <rfi at contesting.com>
>Subject: Re: [RFI] Apple and Motorola Wall Chargers
>
>Don't use any after market Apple Power supplies. They are horribly made linear supplies, which might be quiet, but they are badly designed, single rectifier, bad circuit board layout. There is a not really confirmed rumor that a person in China was electrocuted by one of the knock-offs.
>
>The Apple unit is a well designed switcher, which as far as I know, is quiet, and will charge iPhones and iPads at a high rate quickly and safely. 
>
>Note that Apple has a trade in program for people who bought the counterfeit supplies, trade it in, and Apple will sell you a real one for 10 dollars. Which isn't too bad, considering, they are replacing something that the maker of the counterfeit P.S. won't.
>
>But back to the real Apple supply, with it being quiet, there probably isn't much need to replace it. If you really don't want it, charge the iPad off a USB - although it will be slower. 
>
>- 73  Mike N3LI -
>
>
>On Aug 15, 2013, at 5:18 PM, qrv at kd4e.com wrote:
>
>> There's an aftermarket one of those white things that is a RFI-monster!
>> 
>> It has since died but I cleaned it up by plugging it into a well-filtered power strip.
>> 
>> I don't do Apple stuff, other then the two teens have iPods, so
>> can't help with alternatives.
>
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