> "...The mechanism that causes all of that noise is the rectifier diodes.
> If you use diodes that have a long minority carrier lifetime, no problem,
> but with the faster diodes that are being used nowadays..."
That's a new one on me. I had not heard of RFI/EMI generated by PN junction
switching in linear-mode power supplies. In reading through Dallas
Lankford's description, I was initially certain he was discussing a Radio
Shack switch-mode supply until I saw the simplicity of the circuit in the
photos.
What types of short minority carrier lifetime diodes are the culprits and
why are they now being used in linear power supplies in place of the
garden-variety 1N400x types?
Paul, W9AC
----- Original Message -----
From: "Martin Ewing" <martin.s.ewing@gmail.com>
Cc: "RFI List" <rfi@contesting.com>
Sent: Tuesday, January 12, 2010 11:08 AM
Subject: Re: [RFI] New switching wallwarts - RFI potential?
Interesting about LF EMC, but no info on the new switching supplies.
I have done no serious tests, but so far have not seen any issues with
the new generation mini-switching wall-warts -- and they are really
proliferating around here.
73 Martin AA6E
On Tue, Jan 12, 2010 at 10:53 AM, Tim Duffy K3LR <k3lr@k3lr.com> wrote:
> Hi Pete!
>
> Here is a great paper on wallwarts.
>
> http://www.kongsfjord.no/dl/Antennas/Low%20Noise%20Active%20Antennas%20AC-DC
> %20Power%20Supplies%20II.pdf
>
>
> 73,
> Tim K3LR
>
> -----Original Message-----
> From: rfi-bounces@contesting.com [mailto:rfi-bounces@contesting.com] On
> Behalf Of Pete Smith N4ZR
> Sent: Tuesday, January 12, 2010 9:36 AM
> To: RFI List
> Subject: [RFI] New switching wallwarts - RFI potential?
>
> Recently, I have begun receiving a new type of wall-wart with various
> pieces of consumer equipment and, most recently, with my QS1R SDR. Ones
> I've seen have generally been for 5 volts at 1 amp, are much lighter
> than the old ones, and I even got one that said Switching Adapter on the
> side.
>
> It also claimed, of course, to be FCC approved and UL listed, but no CE.
>
> These adapters are very attractive - in addition to the high current
> rating they are narrow, so that 6 of them would fit on a 6-hole surge
> suppressor, even without wall-wart-spaced outlets. but I'm a little
> concerned - I don't think I'm hearing mine, but my shack is a long way
> from my antennas.
>
> Has anyone had occasion to test these critters?
>
> --
> 73, Pete N4ZR
> Visit the Contesting Compendium at http://wiki.contesting.com
> The World Contest Station Database, updated daily at
> www.conteststations.com
> The Reverse Beacon Network at http://reversebeacon.net
>
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--
Dr. Martin S. Ewing, AA6E
Member IEEE, URSI, AAS, ARRL
Branford, Connecticut
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