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@psu.edu>
>Sent: Aug 15, 2013 7:56 PM
>To: Rfi List <rfi@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@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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