[RFI] Investigating receive noise - got a few questions

[Jim Brown]

Hi Michael,

My test is pretty simple -- a Kenwood TH-F6A talkie tuned a bit above 2 
MHz used as a probe.  Testing with a receiver working into your antenna 
is NOT always a good test, because there are so many other noise sources 
that combine to obscure one of them alone.  The average home probably 
has a couple of dozen switchers by 2018 -- they come in the door with 
virtually everything we buy that plugs into the wall! Some are wall 
warts, some are built into the equipment itself.

Yes, there are good switchers and bad ones. All of those that have come 
with my Thinkpads have been quiet. Some used switchers I found built for 
use with Motorola gear are quiet. So is a 20A supply built for use by 
hams. And so is the switcher in Elecraft's new KPA1500 power amp. Nearly 
all that came with other stuff are not.

73, Jim K9YC

On 11/29/2018 11:36 AM, Michael Coslo wrote:
> It seems to be a popular thing to condemn every switcher as noisy. Whenever I purchase something that comes with a wall wart, I check it out with my radio on all bands. Most pass.
>
> What is more, if we willy nilly replace the dreaded switchers with the linear, we could actually cause problems where one did not exist.
>
> Being built to be cheap, the linears I have seen have a transformer, a full wave rectifier, and a filter cap. My experience with Linear wall warts echos this http://www.dxing.info/equipment/wall_warts_bryant.dx
>
> If an Op wants to have no switchers, and if they want clean power. make a power distribution system with a well regulated, properly filtered power supply, and not allow a wall wart to be seen in their house.
>
> But really, check out that switcher before trashing it. You aren’t gaining a lot by going to a cheap linear wart, and might introduce problems.
>
>
>
> - Michael Coslo -
> Frequency Coordinator, Beaver Stadium
> 814-404-3991
> mjc5 at psu.edu
> mjcn3li at gmail.com
>
>> On Nov 28, 2018, at 11:14 PM, Roger (K8RI) <k8ri at rogerhalstead.com> wrote:
>>
>> One thing to keep in mind and this list seems to ignore. Not all switching supplies generate noise although many, if not most do.
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